14 files changed, 9594 insertions, 0 deletions
diff --git a/src/lib-sql/Makefile.am b/src/lib-sql/Makefile.am
new file mode 100644
index 0000000..89c3d2d
--- /dev/null
+++ b/src/lib-sql/Makefile.am
@@ -0,0 +1,144 @@
+noinst_LTLIBRARIES = libsql.la libdriver_test.la
+
+SQL_DRIVER_PLUGINS =
+
+# automake seems to force making this unconditional..
+NOPLUGIN_LDFLAGS =
+
+if SQL_PLUGINS
+if BUILD_MYSQL
+MYSQL_LIB = libdriver_mysql.la
+SQL_DRIVER_PLUGINS += mysql
+endif
+if BUILD_PGSQL
+PGSQL_LIB = libdriver_pgsql.la
+SQL_DRIVER_PLUGINS += pgsql
+endif
+if BUILD_SQLITE
+SQLITE_LIB = libdriver_sqlite.la
+SQL_DRIVER_PLUGINS += sqlite
+endif
+if BUILD_CASSANDRA
+CASSANDRA_LIB = libdriver_cassandra.la
+SQL_DRIVER_PLUGINS += cassandra
+endif
+
+sql_module_LTLIBRARIES = \
+	$(MYSQL_LIB) \
+	$(PGSQL_LIB) \
+	$(SQLITE_LIB) \
+	$(CASSANDRA_LIB)
+
+sql_moduledir = $(moduledir)
+endif
+
+sql_drivers = @sql_drivers@
+
+AM_CPPFLAGS = \
+	-I$(top_srcdir)/src/lib \
+	-I$(top_srcdir)/src/lib-settings \
+	$(SQL_CFLAGS)
+
+dist_sources = \
+	sql-api.c \
+	sql-db-cache.c
+
+if ! SQL_PLUGINS
+driver_sources = \
+	driver-mysql.c \
+	driver-pgsql.c \
+	driver-sqlite.c \
+	driver-cassandra.c
+endif
+
+libsql_la_SOURCES = \
+	$(dist_sources) \
+	$(driver_sources) \
+	driver-sqlpool.c
+libsql_la_LIBADD = $(SQL_LIBS)
+
+nodist_libsql_la_SOURCES = sql-drivers-register.c
+
+deplibs = \
+	../lib-dovecot/libdovecot.la
+
+if SQL_PLUGINS
+libdriver_mysql_la_LDFLAGS = -module -avoid-version
+libdriver_mysql_la_LIBADD = $(MYSQL_LIBS)
+libdriver_mysql_la_CPPFLAGS = $(AM_CPPFLAGS) $(MYSQL_CFLAGS)
+libdriver_mysql_la_SOURCES = driver-mysql.c
+
+libdriver_pgsql_la_LDFLAGS = -module -avoid-version
+libdriver_pgsql_la_LIBADD = $(PGSQL_LIBS)
+libdriver_pgsql_la_CPPFLAGS = $(AM_CPPFLAGS) $(PGSQL_CFLAGS)
+libdriver_pgsql_la_SOURCES = driver-pgsql.c
+
+libdriver_sqlite_la_LDFLAGS = -module -avoid-version
+libdriver_sqlite_la_LIBADD = $(SQLITE_LIBS)
+libdriver_sqlite_la_CPPFLAGS = $(AM_CPPFLAGS) $(SQLITE_CFLAGS)
+libdriver_sqlite_la_SOURCES = driver-sqlite.c
+
+libdriver_cassandra_la_LDFLAGS = -module -avoid-version
+libdriver_cassandra_la_LIBADD = $(CASSANDRA_LIBS)
+libdriver_cassandra_la_CPPFLAGS = $(AM_CPPFLAGS) $(CASSANDRA_CFLAGS)
+libdriver_cassandra_la_SOURCES = driver-cassandra.c
+else
+endif
+
+libdriver_test_la_LDFLAGS = -avoid-version
+libdriver_test_la_CPPFLAGS = $(AM_CPPFLAGS) \
+	-I$(top_srcdir)/src/lib-test
+libdriver_test_la_SOURCES = driver-test.c
+
+noinst_HEADERS = driver-test.h
+
+pkglib_LTLIBRARIES = libdovecot-sql.la
+libdovecot_sql_la_SOURCES = 
+libdovecot_sql_la_LIBADD = libsql.la $(deplibs)
+libdovecot_sql_la_DEPENDENCIES = libsql.la
+libdovecot_sql_la_LDFLAGS = -export-dynamic
+
+headers = \
+	sql-api.h \
+	sql-api-private.h \
+	sql-db-cache.h
+
+pkginc_libdir=$(pkgincludedir)
+pkginc_lib_HEADERS = $(headers)
+
+sql-drivers-register.c: Makefile
+	rm -f $@
+	echo '/* this file automatically generated by Makefile */' >$@
+	echo '#include "lib.h"' >>$@
+	echo '#include "sql-api.h"' >>$@
+if ! SQL_PLUGINS
+	for i in $(sql_drivers) null; do \
+	  if [ "$${i}" != "null" ]; then \
+	        echo "extern struct sql_db driver_$${i}_db;" >>$@ ; \
+	  fi; \
+	done
+endif
+	echo 'void sql_drivers_register_all(void) {' >>$@
+if ! SQL_PLUGINS
+	for i in $(sql_drivers) null; do \
+	  if [ "$${i}" != "null" ]; then \
+	        echo "sql_driver_register(&driver_$${i}_db);" >>$@ ; \
+	  fi; \
+	done
+endif
+	echo '}' >>$@
+
+if SQL_PLUGINS
+install-exec-local:
+	for d in auth dict; do \
+	  $(mkdir_p) $(DESTDIR)$(moduledir)/$$d; \
+	  for driver in $(SQL_DRIVER_PLUGINS); do \
+	    rm -f $(DESTDIR)$(moduledir)/$$d/libdriver_$$driver.so; \
+	    $(LN_S) ../libdriver_$$driver.so $(DESTDIR)$(moduledir)/$$d; \
+	  done; \
+	done
+endif
+
+
+distclean-generic:
+	rm -f Makefile sql-drivers-register.c
diff --git a/src/lib-sql/Makefile.in b/src/lib-sql/Makefile.in
new file mode 100644
index 0000000..e807466
--- /dev/null
+++ b/src/lib-sql/Makefile.in
@@ -0,0 +1,1159 @@
+# Makefile.in generated by automake 1.16.1 from Makefile.am.
+# @configure_input@
+
+# Copyright (C) 1994-2018 Free Software Foundation, Inc.
+
+# This Makefile.in is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY, to the extent permitted by law; without
+# even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+# PARTICULAR PURPOSE.
+
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+
+
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+@BUILD_SQLITE_TRUE@@SQL_PLUGINS_TRUE@am__append_3 = sqlite
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+	./$(DEPDIR)/libdriver_mysql_la-driver-mysql.Plo \
+	./$(DEPDIR)/libdriver_pgsql_la-driver-pgsql.Plo \
+	./$(DEPDIR)/libdriver_sqlite_la-driver-sqlite.Plo \
+	./$(DEPDIR)/libdriver_test_la-driver-test.Plo \
+	./$(DEPDIR)/sql-api.Plo ./$(DEPDIR)/sql-db-cache.Plo \
+	./$(DEPDIR)/sql-drivers-register.Plo
+am__mv = mv -f
+COMPILE = $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) \
+	$(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS)
+LTCOMPILE = $(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) \
+	$(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) \
+	$(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) \
+	$(AM_CFLAGS) $(CFLAGS)
+AM_V_CC = $(am__v_CC_@AM_V@)
+am__v_CC_ = $(am__v_CC_@AM_DEFAULT_V@)
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+LINK = $(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) \
+	$(LIBTOOLFLAGS) --mode=link $(CCLD) $(AM_CFLAGS) $(CFLAGS) \
+	$(AM_LDFLAGS) $(LDFLAGS) -o $@
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+am__v_CCLD_0 = @echo "  CCLD    " $@;
+am__v_CCLD_1 = 
+SOURCES = $(libdovecot_sql_la_SOURCES) \
+	$(libdriver_cassandra_la_SOURCES) \
+	$(libdriver_mysql_la_SOURCES) $(libdriver_pgsql_la_SOURCES) \
+	$(libdriver_sqlite_la_SOURCES) $(libdriver_test_la_SOURCES) \
+	$(libsql_la_SOURCES) $(nodist_libsql_la_SOURCES)
+DIST_SOURCES = $(libdovecot_sql_la_SOURCES) \
+	$(am__libdriver_cassandra_la_SOURCES_DIST) \
+	$(am__libdriver_mysql_la_SOURCES_DIST) \
+	$(am__libdriver_pgsql_la_SOURCES_DIST) \
+	$(am__libdriver_sqlite_la_SOURCES_DIST) \
+	$(libdriver_test_la_SOURCES) $(am__libsql_la_SOURCES_DIST)
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+    n|no|NO) false;; \
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+  { items[$$0] = 1; nonempty = 1; } \
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+'
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+# e.g., the same source file might be shared among _SOURCES variables
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+am__define_uniq_tagged_files = \
+  list='$(am__tagged_files)'; \
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+MYSQL_CONFIG = @MYSQL_CONFIG@
+MYSQL_LIBS = @MYSQL_LIBS@
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+
+# automake seems to force making this unconditional..
+NOPLUGIN_LDFLAGS = 
+OBJDUMP = @OBJDUMP@
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+top_builddir = @top_builddir@
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+noinst_LTLIBRARIES = libsql.la libdriver_test.la
+SQL_DRIVER_PLUGINS = $(am__append_1) $(am__append_2) $(am__append_3) \
+	$(am__append_4)
+@BUILD_MYSQL_TRUE@@SQL_PLUGINS_TRUE@MYSQL_LIB = libdriver_mysql.la
+@BUILD_PGSQL_TRUE@@SQL_PLUGINS_TRUE@PGSQL_LIB = libdriver_pgsql.la
+@BUILD_SQLITE_TRUE@@SQL_PLUGINS_TRUE@SQLITE_LIB = libdriver_sqlite.la
+@BUILD_CASSANDRA_TRUE@@SQL_PLUGINS_TRUE@CASSANDRA_LIB = libdriver_cassandra.la
+@SQL_PLUGINS_TRUE@sql_module_LTLIBRARIES = \
+@SQL_PLUGINS_TRUE@	$(MYSQL_LIB) \
+@SQL_PLUGINS_TRUE@	$(PGSQL_LIB) \
+@SQL_PLUGINS_TRUE@	$(SQLITE_LIB) \
+@SQL_PLUGINS_TRUE@	$(CASSANDRA_LIB)
+
+@SQL_PLUGINS_TRUE@sql_moduledir = $(moduledir)
+AM_CPPFLAGS = \
+	-I$(top_srcdir)/src/lib \
+	-I$(top_srcdir)/src/lib-settings \
+	$(SQL_CFLAGS)
+
+dist_sources = \
+	sql-api.c \
+	sql-db-cache.c
+
+@SQL_PLUGINS_FALSE@driver_sources = \
+@SQL_PLUGINS_FALSE@	driver-mysql.c \
+@SQL_PLUGINS_FALSE@	driver-pgsql.c \
+@SQL_PLUGINS_FALSE@	driver-sqlite.c \
+@SQL_PLUGINS_FALSE@	driver-cassandra.c
+
+libsql_la_SOURCES = \
+	$(dist_sources) \
+	$(driver_sources) \
+	driver-sqlpool.c
+
+libsql_la_LIBADD = $(SQL_LIBS)
+nodist_libsql_la_SOURCES = sql-drivers-register.c
+deplibs = \
+	../lib-dovecot/libdovecot.la
+
+@SQL_PLUGINS_TRUE@libdriver_mysql_la_LDFLAGS = -module -avoid-version
+@SQL_PLUGINS_TRUE@libdriver_mysql_la_LIBADD = $(MYSQL_LIBS)
+@SQL_PLUGINS_TRUE@libdriver_mysql_la_CPPFLAGS = $(AM_CPPFLAGS) $(MYSQL_CFLAGS)
+@SQL_PLUGINS_TRUE@libdriver_mysql_la_SOURCES = driver-mysql.c
+@SQL_PLUGINS_TRUE@libdriver_pgsql_la_LDFLAGS = -module -avoid-version
+@SQL_PLUGINS_TRUE@libdriver_pgsql_la_LIBADD = $(PGSQL_LIBS)
+@SQL_PLUGINS_TRUE@libdriver_pgsql_la_CPPFLAGS = $(AM_CPPFLAGS) $(PGSQL_CFLAGS)
+@SQL_PLUGINS_TRUE@libdriver_pgsql_la_SOURCES = driver-pgsql.c
+@SQL_PLUGINS_TRUE@libdriver_sqlite_la_LDFLAGS = -module -avoid-version
+@SQL_PLUGINS_TRUE@libdriver_sqlite_la_LIBADD = $(SQLITE_LIBS)
+@SQL_PLUGINS_TRUE@libdriver_sqlite_la_CPPFLAGS = $(AM_CPPFLAGS) $(SQLITE_CFLAGS)
+@SQL_PLUGINS_TRUE@libdriver_sqlite_la_SOURCES = driver-sqlite.c
+@SQL_PLUGINS_TRUE@libdriver_cassandra_la_LDFLAGS = -module -avoid-version
+@SQL_PLUGINS_TRUE@libdriver_cassandra_la_LIBADD = $(CASSANDRA_LIBS)
+@SQL_PLUGINS_TRUE@libdriver_cassandra_la_CPPFLAGS = $(AM_CPPFLAGS) $(CASSANDRA_CFLAGS)
+@SQL_PLUGINS_TRUE@libdriver_cassandra_la_SOURCES = driver-cassandra.c
+libdriver_test_la_LDFLAGS = -avoid-version
+libdriver_test_la_CPPFLAGS = $(AM_CPPFLAGS) \
+	-I$(top_srcdir)/src/lib-test
+
+libdriver_test_la_SOURCES = driver-test.c
+noinst_HEADERS = driver-test.h
+pkglib_LTLIBRARIES = libdovecot-sql.la
+libdovecot_sql_la_SOURCES = 
+libdovecot_sql_la_LIBADD = libsql.la $(deplibs)
+libdovecot_sql_la_DEPENDENCIES = libsql.la
+libdovecot_sql_la_LDFLAGS = -export-dynamic
+headers = \
+	sql-api.h \
+	sql-api-private.h \
+	sql-db-cache.h
+
+pkginc_libdir = $(pkgincludedir)
+pkginc_lib_HEADERS = $(headers)
+all: all-am
+
+.SUFFIXES:
+.SUFFIXES: .c .lo .o .obj
+$(srcdir)/Makefile.in: @MAINTAINER_MODE_TRUE@ $(srcdir)/Makefile.am  $(am__configure_deps)
+	@for dep in $?; do \
+	  case '$(am__configure_deps)' in \
+	    *$$dep*) \
+	      ( cd $(top_builddir) && $(MAKE) $(AM_MAKEFLAGS) am--refresh ) \
+	        && { if test -f $@; then exit 0; else break; fi; }; \
+	      exit 1;; \
+	  esac; \
+	done; \
+	echo ' cd $(top_srcdir) && $(AUTOMAKE) --foreign src/lib-sql/Makefile'; \
+	$(am__cd) $(top_srcdir) && \
+	  $(AUTOMAKE) --foreign src/lib-sql/Makefile
+Makefile: $(srcdir)/Makefile.in $(top_builddir)/config.status
+	@case '$?' in \
+	  *config.status*) \
+	    cd $(top_builddir) && $(MAKE) $(AM_MAKEFLAGS) am--refresh;; \
+	  *) \
+	    echo ' cd $(top_builddir) && $(SHELL) ./config.status $(subdir)/$@ $(am__maybe_remake_depfiles)'; \
+	    cd $(top_builddir) && $(SHELL) ./config.status $(subdir)/$@ $(am__maybe_remake_depfiles);; \
+	esac;
+
+$(top_builddir)/config.status: $(top_srcdir)/configure $(CONFIG_STATUS_DEPENDENCIES)
+	cd $(top_builddir) && $(MAKE) $(AM_MAKEFLAGS) am--refresh
+
+$(top_srcdir)/configure: @MAINTAINER_MODE_TRUE@ $(am__configure_deps)
+	cd $(top_builddir) && $(MAKE) $(AM_MAKEFLAGS) am--refresh
+$(ACLOCAL_M4): @MAINTAINER_MODE_TRUE@ $(am__aclocal_m4_deps)
+	cd $(top_builddir) && $(MAKE) $(AM_MAKEFLAGS) am--refresh
+$(am__aclocal_m4_deps):
+
+clean-noinstLTLIBRARIES:
+	-test -z "$(noinst_LTLIBRARIES)" || rm -f $(noinst_LTLIBRARIES)
+	@list='$(noinst_LTLIBRARIES)'; \
+	locs=`for p in $$list; do echo $$p; done | \
+	      sed 's|^[^/]*$$|.|; s|/[^/]*$$||; s|$$|/so_locations|' | \
+	      sort -u`; \
+	test -z "$$locs" || { \
+	  echo rm -f $${locs}; \
+	  rm -f $${locs}; \
+	}
+
+install-pkglibLTLIBRARIES: $(pkglib_LTLIBRARIES)
+	@$(NORMAL_INSTALL)
+	@list='$(pkglib_LTLIBRARIES)'; test -n "$(pkglibdir)" || list=; \
+	list2=; for p in $$list; do \
+	  if test -f $$p; then \
+	    list2="$$list2 $$p"; \
+	  else :; fi; \
+	done; \
+	test -z "$$list2" || { \
+	  echo " $(MKDIR_P) '$(DESTDIR)$(pkglibdir)'"; \
+	  $(MKDIR_P) "$(DESTDIR)$(pkglibdir)" || exit 1; \
+	  echo " $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=install $(INSTALL) $(INSTALL_STRIP_FLAG) $$list2 '$(DESTDIR)$(pkglibdir)'"; \
+	  $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=install $(INSTALL) $(INSTALL_STRIP_FLAG) $$list2 "$(DESTDIR)$(pkglibdir)"; \
+	}
+
+uninstall-pkglibLTLIBRARIES:
+	@$(NORMAL_UNINSTALL)
+	@list='$(pkglib_LTLIBRARIES)'; test -n "$(pkglibdir)" || list=; \
+	for p in $$list; do \
+	  $(am__strip_dir) \
+	  echo " $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=uninstall rm -f '$(DESTDIR)$(pkglibdir)/$$f'"; \
+	  $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=uninstall rm -f "$(DESTDIR)$(pkglibdir)/$$f"; \
+	done
+
+clean-pkglibLTLIBRARIES:
+	-test -z "$(pkglib_LTLIBRARIES)" || rm -f $(pkglib_LTLIBRARIES)
+	@list='$(pkglib_LTLIBRARIES)'; \
+	locs=`for p in $$list; do echo $$p; done | \
+	      sed 's|^[^/]*$$|.|; s|/[^/]*$$||; s|$$|/so_locations|' | \
+	      sort -u`; \
+	test -z "$$locs" || { \
+	  echo rm -f $${locs}; \
+	  rm -f $${locs}; \
+	}
+
+install-sql_moduleLTLIBRARIES: $(sql_module_LTLIBRARIES)
+	@$(NORMAL_INSTALL)
+	@list='$(sql_module_LTLIBRARIES)'; test -n "$(sql_moduledir)" || list=; \
+	list2=; for p in $$list; do \
+	  if test -f $$p; then \
+	    list2="$$list2 $$p"; \
+	  else :; fi; \
+	done; \
+	test -z "$$list2" || { \
+	  echo " $(MKDIR_P) '$(DESTDIR)$(sql_moduledir)'"; \
+	  $(MKDIR_P) "$(DESTDIR)$(sql_moduledir)" || exit 1; \
+	  echo " $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=install $(INSTALL) $(INSTALL_STRIP_FLAG) $$list2 '$(DESTDIR)$(sql_moduledir)'"; \
+	  $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=install $(INSTALL) $(INSTALL_STRIP_FLAG) $$list2 "$(DESTDIR)$(sql_moduledir)"; \
+	}
+
+uninstall-sql_moduleLTLIBRARIES:
+	@$(NORMAL_UNINSTALL)
+	@list='$(sql_module_LTLIBRARIES)'; test -n "$(sql_moduledir)" || list=; \
+	for p in $$list; do \
+	  $(am__strip_dir) \
+	  echo " $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=uninstall rm -f '$(DESTDIR)$(sql_moduledir)/$$f'"; \
+	  $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=uninstall rm -f "$(DESTDIR)$(sql_moduledir)/$$f"; \
+	done
+
+clean-sql_moduleLTLIBRARIES:
+	-test -z "$(sql_module_LTLIBRARIES)" || rm -f $(sql_module_LTLIBRARIES)
+	@list='$(sql_module_LTLIBRARIES)'; \
+	locs=`for p in $$list; do echo $$p; done | \
+	      sed 's|^[^/]*$$|.|; s|/[^/]*$$||; s|$$|/so_locations|' | \
+	      sort -u`; \
+	test -z "$$locs" || { \
+	  echo rm -f $${locs}; \
+	  rm -f $${locs}; \
+	}
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+	-rm -f ./$(DEPDIR)/libdriver_test_la-driver-test.Plo
+	-rm -f ./$(DEPDIR)/sql-api.Plo
+	-rm -f ./$(DEPDIR)/sql-db-cache.Plo
+	-rm -f ./$(DEPDIR)/sql-drivers-register.Plo
+	-rm -f Makefile
+maintainer-clean-am: distclean-am maintainer-clean-generic
+
+mostlyclean: mostlyclean-am
+
+mostlyclean-am: mostlyclean-compile mostlyclean-generic \
+	mostlyclean-libtool
+
+pdf: pdf-am
+
+pdf-am:
+
+ps: ps-am
+
+ps-am:
+
+uninstall-am: uninstall-pkginc_libHEADERS uninstall-pkglibLTLIBRARIES \
+	uninstall-sql_moduleLTLIBRARIES
+
+.MAKE: install-am install-strip
+
+.PHONY: CTAGS GTAGS TAGS all all-am am--depfiles check check-am clean \
+	clean-generic clean-libtool clean-noinstLTLIBRARIES \
+	clean-pkglibLTLIBRARIES clean-sql_moduleLTLIBRARIES \
+	cscopelist-am ctags ctags-am distclean distclean-compile \
+	distclean-generic distclean-libtool distclean-tags distdir dvi \
+	dvi-am html html-am info info-am install install-am \
+	install-data install-data-am install-dvi install-dvi-am \
+	install-exec install-exec-am install-exec-local install-html \
+	install-html-am install-info install-info-am install-man \
+	install-pdf install-pdf-am install-pkginc_libHEADERS \
+	install-pkglibLTLIBRARIES install-ps install-ps-am \
+	install-sql_moduleLTLIBRARIES install-strip installcheck \
+	installcheck-am installdirs maintainer-clean \
+	maintainer-clean-generic mostlyclean mostlyclean-compile \
+	mostlyclean-generic mostlyclean-libtool pdf pdf-am ps ps-am \
+	tags tags-am uninstall uninstall-am \
+	uninstall-pkginc_libHEADERS uninstall-pkglibLTLIBRARIES \
+	uninstall-sql_moduleLTLIBRARIES
+
+.PRECIOUS: Makefile
+
+
+sql-drivers-register.c: Makefile
+	rm -f $@
+	echo '/* this file automatically generated by Makefile */' >$@
+	echo '#include "lib.h"' >>$@
+	echo '#include "sql-api.h"' >>$@
+@SQL_PLUGINS_FALSE@	for i in $(sql_drivers) null; do \
+@SQL_PLUGINS_FALSE@	  if [ "$${i}" != "null" ]; then \
+@SQL_PLUGINS_FALSE@	        echo "extern struct sql_db driver_$${i}_db;" >>$@ ; \
+@SQL_PLUGINS_FALSE@	  fi; \
+@SQL_PLUGINS_FALSE@	done
+	echo 'void sql_drivers_register_all(void) {' >>$@
+@SQL_PLUGINS_FALSE@	for i in $(sql_drivers) null; do \
+@SQL_PLUGINS_FALSE@	  if [ "$${i}" != "null" ]; then \
+@SQL_PLUGINS_FALSE@	        echo "sql_driver_register(&driver_$${i}_db);" >>$@ ; \
+@SQL_PLUGINS_FALSE@	  fi; \
+@SQL_PLUGINS_FALSE@	done
+	echo '}' >>$@
+
+@SQL_PLUGINS_TRUE@install-exec-local:
+@SQL_PLUGINS_TRUE@	for d in auth dict; do \
+@SQL_PLUGINS_TRUE@	  $(mkdir_p) $(DESTDIR)$(moduledir)/$$d; \
+@SQL_PLUGINS_TRUE@	  for driver in $(SQL_DRIVER_PLUGINS); do \
+@SQL_PLUGINS_TRUE@	    rm -f $(DESTDIR)$(moduledir)/$$d/libdriver_$$driver.so; \
+@SQL_PLUGINS_TRUE@	    $(LN_S) ../libdriver_$$driver.so $(DESTDIR)$(moduledir)/$$d; \
+@SQL_PLUGINS_TRUE@	  done; \
+@SQL_PLUGINS_TRUE@	done
+
+distclean-generic:
+	rm -f Makefile sql-drivers-register.c
+
+# Tell versions [3.59,3.63) of GNU make to not export all variables.
+# Otherwise a system limit (for SysV at least) may be exceeded.
+.NOEXPORT:
diff --git a/src/lib-sql/driver-cassandra.c b/src/lib-sql/driver-cassandra.c
new file mode 100644
index 0000000..4e66809
--- /dev/null
+++ b/src/lib-sql/driver-cassandra.c
@@ -0,0 +1,2579 @@
+/* Copyright (c) 2015-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "istream.h"
+#include "array.h"
+#include "hostpid.h"
+#include "hex-binary.h"
+#include "str.h"
+#include "ioloop.h"
+#include "net.h"
+#include "write-full.h"
+#include "time-util.h"
+#include "var-expand.h"
+#include "safe-memset.h"
+#include "settings-parser.h"
+#include "sql-api-private.h"
+
+#ifdef BUILD_CASSANDRA
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <cassandra.h>
+#include <pthread.h>
+
+#define IS_CONNECTED(db) \
+	((db)->api.state != SQL_DB_STATE_DISCONNECTED && \
+	 (db)->api.state != SQL_DB_STATE_CONNECTING)
+
+#define CASSANDRA_FALLBACK_WARN_INTERVAL_SECS 60
+#define CASSANDRA_FALLBACK_FIRST_RETRY_MSECS 50
+#define CASSANDRA_FALLBACK_MAX_RETRY_MSECS (1000*60)
+
+#define CASS_QUERY_DEFAULT_WARN_TIMEOUT_MSECS (5*1000)
+
+typedef void driver_cassandra_callback_t(CassFuture *future, void *context);
+
+enum cassandra_counter_type {
+	CASSANDRA_COUNTER_TYPE_QUERY_SENT,
+	CASSANDRA_COUNTER_TYPE_QUERY_RECV_OK,
+	CASSANDRA_COUNTER_TYPE_QUERY_RECV_ERR_NO_HOSTS,
+	CASSANDRA_COUNTER_TYPE_QUERY_RECV_ERR_QUEUE_FULL,
+	CASSANDRA_COUNTER_TYPE_QUERY_RECV_ERR_CLIENT_TIMEOUT,
+	CASSANDRA_COUNTER_TYPE_QUERY_RECV_ERR_SERVER_TIMEOUT,
+	CASSANDRA_COUNTER_TYPE_QUERY_RECV_ERR_SERVER_UNAVAILABLE,
+	CASSANDRA_COUNTER_TYPE_QUERY_RECV_ERR_OTHER,
+	CASSANDRA_COUNTER_TYPE_QUERY_SLOW,
+
+	CASSANDRA_COUNTER_COUNT
+};
+static const char *counter_names[CASSANDRA_COUNTER_COUNT] = {
+	"sent",
+	"recv_ok",
+	"recv_err_no_hosts",
+	"recv_err_queue_full",
+	"recv_err_client_timeout",
+	"recv_err_server_timeout",
+	"recv_err_server_unavailable",
+	"recv_err_other",
+	"slow",
+};
+
+enum cassandra_query_type {
+	CASSANDRA_QUERY_TYPE_READ,
+	CASSANDRA_QUERY_TYPE_READ_MORE,
+	CASSANDRA_QUERY_TYPE_WRITE,
+	CASSANDRA_QUERY_TYPE_DELETE,
+
+	CASSANDRA_QUERY_TYPE_COUNT
+};
+
+static const char *cassandra_query_type_names[CASSANDRA_QUERY_TYPE_COUNT] = {
+	"read", "read-more", "write", "delete"
+};
+
+struct cassandra_callback {
+	unsigned int id;
+	struct timeout *to;
+	CassFuture *future;
+	struct cassandra_db *db;
+	driver_cassandra_callback_t *callback;
+	void *context;
+};
+
+struct cassandra_db {
+	struct sql_db api;
+
+	char *hosts, *keyspace, *user, *password;
+	CassConsistency read_consistency, write_consistency, delete_consistency;
+	CassConsistency read_fallback_consistency, write_fallback_consistency;
+	CassConsistency delete_fallback_consistency;
+	CassLogLevel log_level;
+	bool debug_queries;
+	bool latency_aware_routing;
+	bool init_ssl;
+	unsigned int protocol_version;
+	unsigned int num_threads;
+	unsigned int connect_timeout_msecs, request_timeout_msecs;
+	unsigned int warn_timeout_msecs;
+	unsigned int heartbeat_interval_secs, idle_timeout_secs;
+	unsigned int execution_retry_interval_msecs, execution_retry_times;
+	unsigned int page_size;
+	in_port_t port;
+
+	CassCluster *cluster;
+	CassSession *session;
+	CassTimestampGen *timestamp_gen;
+	CassSsl *ssl;
+
+	int fd_pipe[2];
+	struct io *io_pipe;
+	ARRAY(struct cassandra_sql_prepared_statement *) pending_prepares;
+	ARRAY(struct cassandra_callback *) callbacks;
+	ARRAY(struct cassandra_result *) results;
+	unsigned int callback_ids;
+
+	char *metrics_path;
+	char *ssl_ca_file;
+	char *ssl_cert_file;
+	char *ssl_private_key_file;
+	char *ssl_private_key_password;
+	CassSslVerifyFlags ssl_verify_flags;
+
+	struct timeout *to_metrics;
+	uint64_t counters[CASSANDRA_COUNTER_COUNT];
+
+	struct timeval primary_query_last_sent[CASSANDRA_QUERY_TYPE_COUNT];
+	time_t last_fallback_warning[CASSANDRA_QUERY_TYPE_COUNT];
+	unsigned int fallback_failures[CASSANDRA_QUERY_TYPE_COUNT];
+
+	/* for synchronous queries: */
+	struct ioloop *ioloop, *orig_ioloop;
+	struct sql_result *sync_result;
+
+	char *error;
+};
+
+struct cassandra_result {
+	struct sql_result api;
+	CassStatement *statement;
+	const CassResult *result;
+	CassIterator *iterator;
+	char *query;
+	char *error;
+	CassConsistency consistency, fallback_consistency;
+	enum cassandra_query_type query_type;
+	struct timeval page0_start_time, start_time, finish_time;
+	unsigned int row_count, total_row_count, page_num;
+	cass_int64_t timestamp;
+
+	pool_t row_pool;
+	ARRAY_TYPE(const_string) fields;
+	ARRAY(size_t) field_sizes;
+
+	sql_query_callback_t *callback;
+	void *context;
+
+	bool is_prepared:1;
+	bool query_sent:1;
+	bool finished:1;
+	bool paging_continues:1;
+};
+
+struct cassandra_transaction_context {
+	struct sql_transaction_context ctx;
+	int refcount;
+
+	sql_commit_callback_t *callback;
+	void *context;
+
+	struct cassandra_sql_statement *stmt;
+	char *query;
+	cass_int64_t query_timestamp;
+	char *error;
+
+	bool begin_succeeded:1;
+	bool begin_failed:1;
+	bool failed:1;
+};
+
+struct cassandra_sql_arg {
+	unsigned int column_idx;
+
+	char *value_str;
+	const unsigned char *value_binary;
+	size_t value_binary_size;
+	int64_t value_int64;
+};
+
+struct cassandra_sql_statement {
+	struct sql_statement stmt;
+
+	struct cassandra_sql_prepared_statement *prep;
+	CassStatement *cass_stmt;
+
+	ARRAY(struct cassandra_sql_arg) pending_args;
+	cass_int64_t timestamp;
+
+	struct cassandra_result *result;
+};
+
+struct cassandra_sql_prepared_statement {
+	struct sql_prepared_statement prep_stmt;
+
+	/* NULL, until the prepare is asynchronously finished */
+	const CassPrepared *prepared;
+	/* statements waiting for prepare to finish */
+	ARRAY(struct cassandra_sql_statement *) pending_statements;
+	/* an error here will cause the prepare to be retried on the next
+	   execution attempt. */
+	char *error;
+
+	bool pending;
+};
+
+extern const struct sql_db driver_cassandra_db;
+extern const struct sql_result driver_cassandra_result;
+
+static struct {
+	CassConsistency consistency;
+	const char *name;
+} cass_consistency_names[] = {
+	{ CASS_CONSISTENCY_ANY, "any" },
+	{ CASS_CONSISTENCY_ONE, "one" },
+	{ CASS_CONSISTENCY_TWO, "two" },
+	{ CASS_CONSISTENCY_THREE, "three" },
+	{ CASS_CONSISTENCY_QUORUM, "quorum" },
+	{ CASS_CONSISTENCY_ALL, "all" },
+	{ CASS_CONSISTENCY_LOCAL_QUORUM, "local-quorum" },
+	{ CASS_CONSISTENCY_EACH_QUORUM, "each-quorum" },
+	{ CASS_CONSISTENCY_SERIAL, "serial" },
+	{ CASS_CONSISTENCY_LOCAL_SERIAL, "local-serial" },
+	{ CASS_CONSISTENCY_LOCAL_ONE, "local-one" }
+};
+
+static struct {
+	CassLogLevel log_level;
+	const char *name;
+} cass_log_level_names[] = {
+	{ CASS_LOG_CRITICAL, "critical" },
+	{ CASS_LOG_ERROR, "error" },
+	{ CASS_LOG_WARN, "warn" },
+	{ CASS_LOG_INFO, "info" },
+	{ CASS_LOG_DEBUG, "debug" },
+	{ CASS_LOG_TRACE, "trace" }
+};
+
+static struct event_category event_category_cassandra = {
+	.parent = &event_category_sql,
+	.name = "cassandra"
+};
+
+static pthread_t main_thread_id;
+static bool main_thread_id_set;
+
+static void driver_cassandra_prepare_pending(struct cassandra_db *db);
+static void
+prepare_finish_pending_statements(struct cassandra_sql_prepared_statement *prep_stmt);
+static void driver_cassandra_result_send_query(struct cassandra_result *result);
+static void driver_cassandra_send_queries(struct cassandra_db *db);
+static void result_finish(struct cassandra_result *result);
+
+static void log_one_line(const CassLogMessage *message,
+			 enum log_type log_type, const char *log_level_str,
+			 const char *text, size_t text_len)
+{
+	/* NOTE: We may not be in the main thread. We can't use the
+	   standard Dovecot functions that may use data stack. That's why
+	   we can't use i_log_type() in here, but have to re-implement the
+	   internal logging protocol. Otherwise preserve Cassandra's own
+	   logging format. */
+	fprintf(stderr, "\001%c%s %u.%03u %s(%s:%d:%s): %.*s\n",
+		log_type+1, my_pid,
+		(unsigned int)(message->time_ms / 1000),
+		(unsigned int)(message->time_ms % 1000),
+		log_level_str,
+		message->file, message->line, message->function,
+		(int)text_len, text);
+}
+
+static void
+driver_cassandra_log_handler(const CassLogMessage* message,
+			     void *data ATTR_UNUSED)
+{
+	enum log_type log_type = LOG_TYPE_ERROR;
+	const char *log_level_str = "";
+
+	switch (message->severity) {
+	case CASS_LOG_DISABLED:
+	case CASS_LOG_LAST_ENTRY:
+		i_unreached();
+	case CASS_LOG_CRITICAL:
+		log_type = LOG_TYPE_PANIC;
+		break;
+	case CASS_LOG_ERROR:
+		log_type = LOG_TYPE_ERROR;
+		break;
+	case CASS_LOG_WARN:
+		log_type = LOG_TYPE_WARNING;
+		break;
+	case CASS_LOG_INFO:
+		log_type = LOG_TYPE_INFO;
+		break;
+	case CASS_LOG_TRACE:
+		log_level_str = "[TRACE] ";
+		/* fall through */
+	case CASS_LOG_DEBUG:
+		log_type = LOG_TYPE_DEBUG;
+		break;
+	}
+
+	/* Log message may contain LFs, so log each line separately. */
+	const char *p, *line = message->message;
+	while ((p = strchr(line, '\n')) != NULL) {
+		log_one_line(message, log_type, log_level_str, line, p - line);
+		line = p+1;
+	}
+	log_one_line(message, log_type, log_level_str, line, strlen(line));
+}
+
+static void driver_cassandra_init_log(void)
+{
+	failure_callback_t *fatal_callback, *error_callback;
+	failure_callback_t *info_callback, *debug_callback;
+
+	i_get_failure_handlers(&fatal_callback, &error_callback,
+			       &info_callback, &debug_callback);
+	if (i_failure_handler_is_internal(debug_callback)) {
+		/* Using internal logging protocol. Use it ourself to set log
+		   levels correctly. */
+		cass_log_set_callback(driver_cassandra_log_handler, NULL);
+	}
+}
+
+static int consistency_parse(const char *str, CassConsistency *consistency_r)
+{
+	unsigned int i;
+
+	for (i = 0; i < N_ELEMENTS(cass_consistency_names); i++) {
+		if (strcmp(cass_consistency_names[i].name, str) == 0) {
+			*consistency_r = cass_consistency_names[i].consistency;
+			return 0;
+		}
+	}
+	return -1;
+}
+
+static int log_level_parse(const char *str, CassLogLevel *log_level_r)
+{
+	unsigned int i;
+
+	for (i = 0; i < N_ELEMENTS(cass_log_level_names); i++) {
+		if (strcmp(cass_log_level_names[i].name, str) == 0) {
+			*log_level_r = cass_log_level_names[i].log_level;
+			return 0;
+		}
+	}
+	return -1;
+}
+
+static void driver_cassandra_set_state(struct cassandra_db *db,
+				       enum sql_db_state state)
+{
+	/* switch back to original ioloop in case the caller wants to
+	   add/remove timeouts */
+	if (db->ioloop != NULL)
+		io_loop_set_current(db->orig_ioloop);
+	sql_db_set_state(&db->api, state);
+	if (db->ioloop != NULL)
+		io_loop_set_current(db->ioloop);
+}
+
+static void driver_cassandra_close(struct cassandra_db *db, const char *error)
+{
+	struct cassandra_sql_prepared_statement *prep_stmt;
+	struct cassandra_result *const *resultp;
+
+	io_remove(&db->io_pipe);
+	if (db->fd_pipe[0] != -1) {
+		i_close_fd(&db->fd_pipe[0]);
+		i_close_fd(&db->fd_pipe[1]);
+	}
+	driver_cassandra_set_state(db, SQL_DB_STATE_DISCONNECTED);
+
+	array_foreach_elem(&db->pending_prepares, prep_stmt) {
+		prep_stmt->pending = FALSE;
+		prep_stmt->error = i_strdup(error);
+		prepare_finish_pending_statements(prep_stmt);
+	}
+	array_clear(&db->pending_prepares);
+
+	while (array_count(&db->results) > 0) {
+		resultp = array_front(&db->results);
+		if ((*resultp)->error == NULL)
+			(*resultp)->error = i_strdup(error);
+		result_finish(*resultp);
+	}
+
+	if (db->ioloop != NULL) {
+		/* running a sync query, stop it */
+		io_loop_stop(db->ioloop);
+	}
+}
+
+static void driver_cassandra_log_error(struct cassandra_db *db,
+				       CassFuture *future, const char *str)
+{
+	const char *message;
+	size_t size;
+
+	cass_future_error_message(future, &message, &size);
+	e_error(db->api.event, "%s: %.*s", str, (int)size, message);
+}
+
+static struct cassandra_callback *
+cassandra_callback_detach(struct cassandra_db *db, unsigned int id)
+{
+	struct cassandra_callback *cb, *const *cbp;
+
+	/* usually there are only a few callbacks, so don't bother with using
+	   a hash table */
+	array_foreach(&db->callbacks, cbp) {
+		cb = *cbp;
+		if (cb->id == id) {
+			array_delete(&db->callbacks,
+				     array_foreach_idx(&db->callbacks, cbp), 1);
+			return cb;
+		}
+	}
+	return NULL;
+}
+
+static void cassandra_callback_run(struct cassandra_callback *cb)
+{
+	timeout_remove(&cb->to);
+	cb->callback(cb->future, cb->context);
+	cass_future_free(cb->future);
+	i_free(cb);
+}
+
+static void driver_cassandra_future_callback(CassFuture *future ATTR_UNUSED,
+					     void *context)
+{
+	struct cassandra_callback *cb = context;
+
+	if (pthread_equal(pthread_self(), main_thread_id) != 0) {
+		/* called immediately from the main thread. */
+		cassandra_callback_detach(cb->db, cb->id);
+		cb->to = timeout_add_short(0, cassandra_callback_run, cb);
+		return;
+	}
+
+	/* this isn't the main thread - communicate with main thread by
+	   writing the callback id to the pipe. note that we must not use
+	   almost any dovecot functions here because most of them are using
+	   data-stack, which isn't thread-safe. especially don't use
+	   i_error() here. */
+	if (write_full(cb->db->fd_pipe[1], &cb->id, sizeof(cb->id)) < 0) {
+		const char *str = t_strdup_printf(
+			"cassandra: write(pipe) failed: %s\n",
+			strerror(errno));
+		(void)write_full(STDERR_FILENO, str, strlen(str));
+	}
+}
+
+static void driver_cassandra_input_id(struct cassandra_db *db, unsigned int id)
+{
+	struct cassandra_callback *cb;
+
+	cb = cassandra_callback_detach(db, id);
+	if (cb == NULL)
+		i_panic("cassandra: Received unknown ID %u", id);
+	cassandra_callback_run(cb);
+}
+
+static void driver_cassandra_input(struct cassandra_db *db)
+{
+	unsigned int ids[1024];
+	ssize_t ret;
+
+	ret = read(db->fd_pipe[0], ids, sizeof(ids));
+	if (ret < 0)
+		e_error(db->api.event, "read(pipe) failed: %m");
+	else if (ret == 0)
+		e_error(db->api.event, "read(pipe) failed: EOF");
+	else if (ret % sizeof(ids[0]) != 0)
+		e_error(db->api.event, "read(pipe) returned wrong amount of data");
+	else {
+		/* success */
+		unsigned int i, count = ret / sizeof(ids[0]);
+
+		for (i = 0; i < count &&
+			    db->api.state != SQL_DB_STATE_DISCONNECTED; i++)
+			driver_cassandra_input_id(db, ids[i]);
+		return;
+	}
+	driver_cassandra_close(db, "IPC pipe closed");
+}
+
+static void
+driver_cassandra_set_callback(CassFuture *future, struct cassandra_db *db,
+			      driver_cassandra_callback_t *callback,
+			      void *context)
+{
+	struct cassandra_callback *cb;
+
+	i_assert(callback != NULL);
+
+	cb = i_new(struct cassandra_callback, 1);
+	cb->future = future;
+	cb->callback = callback;
+	cb->context = context;
+	cb->db = db;
+
+	array_push_back(&db->callbacks, &cb);
+	cb->id = ++db->callback_ids;
+	if (cb->id == 0)
+		cb->id = ++db->callback_ids;
+
+	/* NOTE: The callback may be called immediately by this same thread.
+	   This is checked within the callback. It may also be called at any
+	   time after this call by another thread. So we must not access "cb"
+	   again after this call. */
+	cass_future_set_callback(future, driver_cassandra_future_callback, cb);
+}
+
+static void connect_callback(CassFuture *future, void *context)
+{
+	struct cassandra_db *db = context;
+
+	if (cass_future_error_code(future) != CASS_OK) {
+		driver_cassandra_log_error(db, future,
+					   "Couldn't connect to Cassandra");
+		driver_cassandra_close(db, "Couldn't connect to Cassandra");
+		return;
+	}
+	driver_cassandra_set_state(db, SQL_DB_STATE_IDLE);
+	if (db->ioloop != NULL) {
+		/* driver_cassandra_sync_init() waiting for connection to
+		   finish */
+		io_loop_stop(db->ioloop);
+	}
+	driver_cassandra_prepare_pending(db);
+	driver_cassandra_send_queries(db);
+}
+
+static int driver_cassandra_connect(struct sql_db *_db)
+{
+	struct cassandra_db *db = (struct cassandra_db *)_db;
+	CassFuture *future;
+
+	i_assert(db->api.state == SQL_DB_STATE_DISCONNECTED);
+
+	if (pipe(db->fd_pipe) < 0) {
+		e_error(_db->event, "pipe() failed: %m");
+		return -1;
+	}
+	db->io_pipe = io_add(db->fd_pipe[0], IO_READ,
+			     driver_cassandra_input, db);
+	driver_cassandra_set_state(db, SQL_DB_STATE_CONNECTING);
+
+	future = cass_session_connect_keyspace(db->session, db->cluster,
+					       db->keyspace);
+	driver_cassandra_set_callback(future, db, connect_callback, db);
+	return 0;
+}
+
+static void driver_cassandra_disconnect(struct sql_db *_db)
+{
+	struct cassandra_db *db = (struct cassandra_db *)_db;
+
+	driver_cassandra_close(db, "Disconnected");
+}
+
+static const char *
+driver_cassandra_escape_string(struct sql_db *db ATTR_UNUSED,
+			       const char *string)
+{
+	string_t *escaped;
+	unsigned int i;
+
+	if (strchr(string, '\'') == NULL)
+		return string;
+	escaped = t_str_new(strlen(string)+10);
+	for (i = 0; string[i] != '\0'; i++) {
+		if (string[i] == '\'')
+			str_append_c(escaped, '\'');
+		str_append_c(escaped, string[i]);
+	}
+	return str_c(escaped);
+}
+
+static int driver_cassandra_parse_connect_string(struct cassandra_db *db,
+						 const char *connect_string,
+						 const char **error_r)
+{
+	const char *const *args, *key, *value, *error;
+	string_t *hosts = t_str_new(64);
+	bool read_fallback_set = FALSE, write_fallback_set = FALSE;
+	bool delete_fallback_set = FALSE;
+
+	db->log_level = CASS_LOG_WARN;
+	db->read_consistency = CASS_CONSISTENCY_LOCAL_QUORUM;
+	db->write_consistency = CASS_CONSISTENCY_LOCAL_QUORUM;
+	db->delete_consistency = CASS_CONSISTENCY_LOCAL_QUORUM;
+	db->connect_timeout_msecs = SQL_CONNECT_TIMEOUT_SECS*1000;
+	db->request_timeout_msecs = SQL_QUERY_TIMEOUT_SECS*1000;
+	db->warn_timeout_msecs = CASS_QUERY_DEFAULT_WARN_TIMEOUT_MSECS;
+
+	args = t_strsplit_spaces(connect_string, " ");
+	for (; *args != NULL; args++) {
+		value = strchr(*args, '=');
+		if (value == NULL) {
+			*error_r = t_strdup_printf(
+				"Missing value in connect string: %s", *args);
+			return -1;
+		}
+		key = t_strdup_until(*args, value++);
+
+		if (str_begins(key, "ssl_"))
+			db->init_ssl = TRUE;
+
+		if (strcmp(key, "host") == 0) {
+			if (str_len(hosts) > 0)
+				str_append_c(hosts, ',');
+			str_append(hosts, value);
+		} else if (strcmp(key, "port") == 0) {
+			if (net_str2port(value, &db->port) < 0) {
+				*error_r = t_strdup_printf(
+					"Invalid port: %s", value);
+				return -1;
+			}
+		} else if (strcmp(key, "dbname") == 0 ||
+			   strcmp(key, "keyspace") == 0) {
+			i_free(db->keyspace);
+			db->keyspace = i_strdup(value);
+		} else if (strcmp(key, "user") == 0) {
+			i_free(db->user);
+			db->user = i_strdup(value);
+		} else if (strcmp(key, "password") == 0) {
+			i_free(db->password);
+			db->password = i_strdup(value);
+		} else if (strcmp(key, "read_consistency") == 0) {
+			if (consistency_parse(value, &db->read_consistency) < 0) {
+				*error_r = t_strdup_printf(
+					"Unknown read_consistency: %s", value);
+				return -1;
+			}
+		} else if (strcmp(key, "read_fallback_consistency") == 0) {
+			if (consistency_parse(value, &db->read_fallback_consistency) < 0) {
+				*error_r = t_strdup_printf(
+					"Unknown read_fallback_consistency: %s", value);
+				return -1;
+			}
+			read_fallback_set = TRUE;
+		} else if (strcmp(key, "write_consistency") == 0) {
+			if (consistency_parse(value,
+					      &db->write_consistency) < 0) {
+				*error_r = t_strdup_printf(
+					"Unknown write_consistency: %s", value);
+				return -1;
+			}
+		} else if (strcmp(key, "write_fallback_consistency") == 0) {
+			if (consistency_parse(value,
+					      &db->write_fallback_consistency) < 0) {
+				*error_r = t_strdup_printf(
+					"Unknown write_fallback_consistency: %s",
+					value);
+				return -1;
+			}
+			write_fallback_set = TRUE;
+		} else if (strcmp(key, "delete_consistency") == 0) {
+			if (consistency_parse(value,
+					      &db->delete_consistency) < 0) {
+				*error_r = t_strdup_printf(
+					"Unknown delete_consistency: %s", value);
+				return -1;
+			}
+		} else if (strcmp(key, "delete_fallback_consistency") == 0) {
+			if (consistency_parse(value,
+					      &db->delete_fallback_consistency) < 0) {
+				*error_r = t_strdup_printf(
+					"Unknown delete_fallback_consistency: %s",
+					value);
+				return -1;
+			}
+			delete_fallback_set = TRUE;
+		} else if (strcmp(key, "log_level") == 0) {
+			if (log_level_parse(value, &db->log_level) < 0) {
+				*error_r = t_strdup_printf(
+					"Unknown log_level: %s", value);
+				return -1;
+			}
+		} else if (strcmp(key, "debug_queries") == 0) {
+			db->debug_queries = TRUE;
+		} else if (strcmp(key, "latency_aware_routing") == 0) {
+			db->latency_aware_routing = TRUE;
+		} else if (strcmp(key, "version") == 0) {
+			if (str_to_uint(value, &db->protocol_version) < 0) {
+				*error_r = t_strdup_printf(
+					"Invalid version: %s", value);
+				return -1;
+			}
+		} else if (strcmp(key, "num_threads") == 0) {
+			if (str_to_uint(value, &db->num_threads) < 0) {
+				*error_r = t_strdup_printf(
+					"Invalid num_threads: %s", value);
+				return -1;
+			}
+		} else if (strcmp(key, "heartbeat_interval") == 0) {
+			if (settings_get_time(value, &db->heartbeat_interval_secs,
+					      &error) < 0) {
+				*error_r = t_strdup_printf(
+					"Invalid heartbeat_interval '%s': %s",
+					value, error);
+				return -1;
+			}
+		} else if (strcmp(key, "idle_timeout") == 0) {
+			if (settings_get_time(value, &db->idle_timeout_secs,
+					      &error) < 0) {
+				*error_r = t_strdup_printf(
+					"Invalid idle_timeout '%s': %s",
+					value, error);
+				return -1;
+			}
+		} else if (strcmp(key, "connect_timeout") == 0) {
+			if (settings_get_time_msecs(value,
+						    &db->connect_timeout_msecs,
+						    &error) < 0) {
+				*error_r = t_strdup_printf(
+					"Invalid connect_timeout '%s': %s",
+					value, error);
+				return -1;
+			}
+		} else if (strcmp(key, "request_timeout") == 0) {
+			if (settings_get_time_msecs(value,
+						    &db->request_timeout_msecs,
+						    &error) < 0) {
+				*error_r = t_strdup_printf(
+					"Invalid request_timeout '%s': %s",
+					value, error);
+				return -1;
+			}
+		} else if (strcmp(key, "warn_timeout") == 0) {
+			if (settings_get_time_msecs(value,
+						    &db->warn_timeout_msecs,
+						    &error) < 0) {
+				*error_r = t_strdup_printf(
+					"Invalid warn_timeout '%s': %s",
+					value, error);
+				return -1;
+			}
+		} else if (strcmp(key, "metrics") == 0) {
+			i_free(db->metrics_path);
+			db->metrics_path = i_strdup(value);
+		} else if (strcmp(key, "execution_retry_interval") == 0) {
+			if (settings_get_time_msecs(value,
+						    &db->execution_retry_interval_msecs,
+						    &error) < 0) {
+				*error_r = t_strdup_printf(
+					"Invalid execution_retry_interval '%s': %s",
+					value, error);
+				return -1;
+			}
+#ifndef HAVE_CASSANDRA_SPECULATIVE_POLICY
+			*error_r = t_strdup_printf(
+	"This cassandra version does not support execution_retry_interval");
+			return -1;
+#endif
+		} else if (strcmp(key, "execution_retry_times") == 0) {
+			if (str_to_uint(value, &db->execution_retry_times) < 0) {
+				*error_r = t_strdup_printf(
+					"Invalid execution_retry_times %s",
+					value);
+				return -1;
+			}
+#ifndef HAVE_CASSANDRA_SPECULATIVE_POLICY
+			*error_r = t_strdup_printf(
+	"This cassandra version does not support execution_retry_times");
+			return -1;
+#endif
+		} else if (strcmp(key, "page_size") == 0) {
+			if (str_to_uint(value, &db->page_size) < 0) {
+				*error_r = t_strdup_printf(
+					"Invalid page_size: %s",
+					value);
+				return -1;
+			}
+		} else if (strcmp(key, "ssl_ca") == 0) {
+			db->ssl_ca_file = i_strdup(value);
+		} else if (strcmp(key, "ssl_cert_file") == 0) {
+			db->ssl_cert_file = i_strdup(value);
+		} else if (strcmp(key, "ssl_private_key_file") == 0) {
+			db->ssl_private_key_file = i_strdup(value);
+		} else if (strcmp(key, "ssl_private_key_password") == 0) {
+			db->ssl_private_key_password = i_strdup(value);
+		} else if (strcmp(key, "ssl_verify") == 0) {
+			if (strcmp(value, "none") == 0) {
+				db->ssl_verify_flags = CASS_SSL_VERIFY_NONE;
+			} else if (strcmp(value, "cert") == 0) {
+				db->ssl_verify_flags = CASS_SSL_VERIFY_PEER_CERT;
+			} else if (strcmp(value, "cert-ip") == 0) {
+				db->ssl_verify_flags =
+					CASS_SSL_VERIFY_PEER_CERT |
+					CASS_SSL_VERIFY_PEER_IDENTITY;
+#if HAVE_DECL_CASS_SSL_VERIFY_PEER_IDENTITY_DNS == 1
+			} else if (strcmp(value, "cert-dns") == 0) {
+				db->ssl_verify_flags =
+					CASS_SSL_VERIFY_PEER_CERT |
+					CASS_SSL_VERIFY_PEER_IDENTITY_DNS;
+#endif
+			} else {
+				*error_r = t_strdup_printf(
+					"Unsupported ssl_verify flags: '%s'",
+					value);
+				return -1;
+			}
+		} else {
+			*error_r = t_strdup_printf(
+				"Unknown connect string: %s", key);
+			return -1;
+		}
+	}
+
+	if (!read_fallback_set)
+		db->read_fallback_consistency = db->read_consistency;
+	if (!write_fallback_set)
+		db->write_fallback_consistency = db->write_consistency;
+	if (!delete_fallback_set)
+		db->delete_fallback_consistency = db->delete_consistency;
+
+	if (str_len(hosts) == 0) {
+		*error_r = t_strdup_printf("No hosts given in connect string");
+		return -1;
+	}
+	if (db->keyspace == NULL) {
+		*error_r = t_strdup_printf("No dbname given in connect string");
+		return -1;
+	}
+
+	if ((db->ssl_cert_file != NULL && db->ssl_private_key_file == NULL) ||
+	    (db->ssl_cert_file == NULL && db->ssl_private_key_file != NULL)) {
+		*error_r = "ssl_cert_file and ssl_private_key_file need to be both set";
+		return -1;
+	}
+
+	db->hosts = i_strdup(str_c(hosts));
+	return 0;
+}
+
+static void
+driver_cassandra_get_metrics_json(struct cassandra_db *db, string_t *dest)
+{
+#define ADD_UINT64(_struct, _field) \
+	str_printfa(dest, "\""#_field"\": %llu,", \
+		(unsigned long long)metrics._struct._field);
+#define ADD_DOUBLE(_struct, _field) \
+	str_printfa(dest, "\""#_field"\": %02lf,", metrics._struct._field);
+	CassMetrics metrics;
+
+	cass_session_get_metrics(db->session, &metrics);
+	str_append(dest, "{ \"requests\": {");
+	ADD_UINT64(requests, min);
+	ADD_UINT64(requests, max);
+	ADD_UINT64(requests, mean);
+	ADD_UINT64(requests, stddev);
+	ADD_UINT64(requests, median);
+	ADD_UINT64(requests, percentile_75th);
+	ADD_UINT64(requests, percentile_95th);
+	ADD_UINT64(requests, percentile_98th);
+	ADD_UINT64(requests, percentile_99th);
+	ADD_UINT64(requests, percentile_999th);
+	ADD_DOUBLE(requests, mean_rate);
+	ADD_DOUBLE(requests, one_minute_rate);
+	ADD_DOUBLE(requests, five_minute_rate);
+	ADD_DOUBLE(requests, fifteen_minute_rate);
+	str_truncate(dest, str_len(dest)-1);
+
+	str_append(dest, "}, \"stats\": {");
+	ADD_UINT64(stats, total_connections);
+	ADD_UINT64(stats, available_connections);
+	ADD_UINT64(stats, exceeded_pending_requests_water_mark);
+	ADD_UINT64(stats, exceeded_write_bytes_water_mark);
+	str_truncate(dest, str_len(dest)-1);
+
+	str_append(dest, "}, \"errors\": {");
+	ADD_UINT64(errors, connection_timeouts);
+	ADD_UINT64(errors, pending_request_timeouts);
+	ADD_UINT64(errors, request_timeouts);
+	str_truncate(dest, str_len(dest)-1);
+
+	str_append(dest, "}, \"queries\": {");
+	for (unsigned int i = 0; i < CASSANDRA_COUNTER_COUNT; i++) {
+		str_printfa(dest, "\"%s\": %"PRIu64",", counter_names[i],
+			    db->counters[i]);
+	}
+	str_truncate(dest, str_len(dest)-1);
+	str_append(dest, "}}");
+}
+
+static void driver_cassandra_metrics_write(struct cassandra_db *db)
+{
+	struct var_expand_table tab[] = {
+		{ '\0', NULL, NULL }
+	};
+	string_t *path = t_str_new(64);
+	string_t *data;
+	const char *error;
+	int fd;
+
+	if (var_expand(path, db->metrics_path, tab, &error) <= 0) {
+		e_error(db->api.event, "Failed to expand metrics_path=%s: %s",
+			db->metrics_path, error);
+		return;
+	}
+
+	fd = open(str_c(path), O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK, 0600);
+	if (fd == -1) {
+		e_error(db->api.event, "creat(%s) failed: %m", str_c(path));
+		return;
+	}
+	data = t_str_new(1024);
+	driver_cassandra_get_metrics_json(db, data);
+	if (write_full(fd, str_data(data), str_len(data)) < 0)
+		e_error(db->api.event, "write(%s) failed: %m", str_c(path));
+	i_close_fd(&fd);
+}
+
+static void driver_cassandra_free(struct cassandra_db **_db)
+{
+	struct cassandra_db *db = *_db;
+	*_db = NULL;
+
+	event_unref(&db->api.event);
+	i_free(db->metrics_path);
+	i_free(db->hosts);
+	i_free(db->error);
+	i_free(db->keyspace);
+	i_free(db->user);
+	i_free(db->password);
+	i_free(db->ssl_ca_file);
+	i_free(db->ssl_cert_file);
+	i_free(db->ssl_private_key_file);
+	i_free_and_null(db->ssl_private_key_password);
+	array_free(&db->api.module_contexts);
+	if (db->ssl != NULL)
+		cass_ssl_free(db->ssl);
+	i_free(db);
+}
+
+static int driver_cassandra_init_ssl(struct cassandra_db *db, const char **error_r)
+{
+	buffer_t *buf = t_buffer_create(512);
+	CassError c_err;
+
+	db->ssl = cass_ssl_new();
+	i_assert(db->ssl != NULL);
+
+	if (db->ssl_ca_file != NULL) {
+		if (buffer_append_full_file(buf, db->ssl_ca_file, SIZE_MAX,
+					    error_r) < 0)
+			return -1;
+		if ((c_err = cass_ssl_add_trusted_cert(db->ssl, str_c(buf))) != CASS_OK) {
+			*error_r = cass_error_desc(c_err);
+			return -1;
+		}
+	}
+
+	if (db->ssl_private_key_file != NULL && db->ssl_cert_file != NULL) {
+		buffer_set_used_size(buf, 0);
+		if (buffer_append_full_file(buf, db->ssl_private_key_file,
+					    SIZE_MAX, error_r) < 0)
+			return -1;
+		c_err = cass_ssl_set_private_key(db->ssl, str_c(buf),
+					         db->ssl_private_key_password);
+		safe_memset(buffer_get_modifiable_data(buf, NULL), 0, buf->used);
+		if (c_err != CASS_OK) {
+			*error_r = cass_error_desc(c_err);
+			return -1;
+		}
+
+		buffer_set_used_size(buf, 0);
+		if (buffer_append_full_file(buf, db->ssl_cert_file, SIZE_MAX, error_r) < 0)
+			return -1;
+		if ((c_err = cass_ssl_set_cert(db->ssl, str_c(buf))) != CASS_OK) {
+			*error_r = cass_error_desc(c_err);
+			return -1;
+		}
+	}
+
+	cass_ssl_set_verify_flags(db->ssl, db->ssl_verify_flags);
+
+	return 0;
+}
+
+static int driver_cassandra_init_full_v(const struct sql_settings *set,
+					struct sql_db **db_r,
+					const char **error_r)
+{
+	struct cassandra_db *db;
+	int ret;
+
+	db = i_new(struct cassandra_db, 1);
+	db->api = driver_cassandra_db;
+	db->fd_pipe[0] = db->fd_pipe[1] = -1;
+	db->api.event = event_create(set->event_parent);
+	event_add_category(db->api.event, &event_category_cassandra);
+	event_set_append_log_prefix(db->api.event, "cassandra: ");
+
+	T_BEGIN {
+		ret = driver_cassandra_parse_connect_string(db,
+			set->connect_string, error_r);
+	} T_END_PASS_STR_IF(ret < 0, error_r);
+
+	if (ret < 0) {
+		driver_cassandra_free(&db);
+		return -1;
+	}
+
+	if (db->init_ssl && driver_cassandra_init_ssl(db, error_r) < 0) {
+		driver_cassandra_free(&db);
+		return -1;
+	}
+
+	driver_cassandra_init_log();
+	cass_log_set_level(db->log_level);
+	if (db->log_level >= CASS_LOG_DEBUG)
+		event_set_forced_debug(db->api.event, TRUE);
+
+	if (db->protocol_version > 0 && db->protocol_version < 4) {
+		/* binding with column indexes requires v4 */
+		db->api.v.prepared_statement_init = NULL;
+		db->api.v.prepared_statement_deinit = NULL;
+		db->api.v.statement_init_prepared = NULL;
+	}
+
+	db->timestamp_gen = cass_timestamp_gen_monotonic_new();
+	db->cluster = cass_cluster_new();
+
+#ifdef HAVE_CASS_CLUSTER_SET_USE_HOSTNAME_RESOLUTION
+	if ((db->ssl_verify_flags & CASS_SSL_VERIFY_PEER_IDENTITY_DNS) != 0) {
+		CassError c_err;
+		if ((c_err = cass_cluster_set_use_hostname_resolution(
+				db->cluster, cass_true)) != CASS_OK) {
+			*error_r = cass_error_desc(c_err);
+			driver_cassandra_free(&db);
+			return -1;
+		}
+	}
+#endif
+	cass_cluster_set_ssl(db->cluster, db->ssl);
+	cass_cluster_set_timestamp_gen(db->cluster, db->timestamp_gen);
+	cass_cluster_set_connect_timeout(db->cluster, db->connect_timeout_msecs);
+	cass_cluster_set_request_timeout(db->cluster, db->request_timeout_msecs);
+	cass_cluster_set_contact_points(db->cluster, db->hosts);
+	if (db->user != NULL && db->password != NULL)
+		cass_cluster_set_credentials(db->cluster, db->user, db->password);
+	if (db->port != 0)
+		cass_cluster_set_port(db->cluster, db->port);
+	if (db->protocol_version != 0)
+		cass_cluster_set_protocol_version(db->cluster, db->protocol_version);
+	if (db->num_threads != 0)
+		cass_cluster_set_num_threads_io(db->cluster, db->num_threads);
+	if (db->latency_aware_routing)
+		cass_cluster_set_latency_aware_routing(db->cluster, cass_true);
+	if (db->heartbeat_interval_secs != 0)
+		cass_cluster_set_connection_heartbeat_interval(db->cluster,
+			db->heartbeat_interval_secs);
+	if (db->idle_timeout_secs != 0)
+		cass_cluster_set_connection_idle_timeout(db->cluster,
+			db->idle_timeout_secs);
+#ifdef HAVE_CASSANDRA_SPECULATIVE_POLICY
+	if (db->execution_retry_times > 0 && db->execution_retry_interval_msecs > 0)
+		cass_cluster_set_constant_speculative_execution_policy(
+			db->cluster, db->execution_retry_interval_msecs,
+			db->execution_retry_times);
+#endif
+	if (db->ssl != NULL) {
+		e_debug(db->api.event, "Enabling TLS for cluster");
+		cass_cluster_set_ssl(db->cluster, db->ssl);
+	}
+	db->session = cass_session_new();
+	if (db->metrics_path != NULL)
+		db->to_metrics = timeout_add(1000, driver_cassandra_metrics_write,
+					     db);
+	i_array_init(&db->results, 16);
+	i_array_init(&db->callbacks, 16);
+	i_array_init(&db->pending_prepares, 16);
+	if (!main_thread_id_set) {
+		main_thread_id = pthread_self();
+		main_thread_id_set = TRUE;
+	}
+
+	*db_r = &db->api;
+	return 0;
+}
+
+static void driver_cassandra_deinit_v(struct sql_db *_db)
+{
+	struct cassandra_db *db = (struct cassandra_db *)_db;
+
+	driver_cassandra_close(db, "Deinitialized");
+
+	i_assert(array_count(&db->callbacks) == 0);
+	array_free(&db->callbacks);
+	i_assert(array_count(&db->results) == 0);
+	array_free(&db->results);
+	i_assert(array_count(&db->pending_prepares) == 0);
+	array_free(&db->pending_prepares);
+
+	cass_session_free(db->session);
+	cass_cluster_free(db->cluster);
+	cass_timestamp_gen_free(db->timestamp_gen);
+	timeout_remove(&db->to_metrics);
+	sql_connection_log_finished(_db);
+	driver_cassandra_free(&db);
+}
+
+static void driver_cassandra_result_unlink(struct cassandra_db *db,
+					   struct cassandra_result *result)
+{
+	struct cassandra_result *const *results;
+	unsigned int i, count;
+
+	results = array_get(&db->results, &count);
+	for (i = 0; i < count; i++) {
+		if (results[i] == result) {
+			array_delete(&db->results, i, 1);
+			return;
+		}
+	}
+	i_unreached();
+}
+
+static void driver_cassandra_log_result(struct cassandra_result *result,
+					bool all_pages, long long reply_usecs)
+{
+	struct cassandra_db *db = (struct cassandra_db *)result->api.db;
+	struct timeval now;
+	unsigned int row_count;
+
+	i_gettimeofday(&now);
+
+	string_t *str = t_str_new(128);
+	str_printfa(str, "Finished %squery '%s' (",
+		    result->is_prepared ? "prepared " : "", result->query);
+	if (result->timestamp != 0)
+		str_printfa(str, "timestamp=%"PRId64", ", result->timestamp);
+	if (all_pages) {
+		str_printfa(str, "%u pages in total, ", result->page_num);
+		row_count = result->total_row_count;
+	} else {
+		if (result->page_num > 0 || result->paging_continues)
+			str_printfa(str, "page %u, ", result->page_num);
+		row_count = result->row_count;
+	}
+	str_printfa(str, "%u rows, %lld+%lld us): %s", row_count, reply_usecs,
+		    timeval_diff_usecs(&now, &result->finish_time),
+		    result->error != NULL ? result->error : "success");
+
+	struct event_passthrough *e =
+		sql_query_finished_event(&db->api, result->api.event,
+					 result->query, result->error == NULL,
+					 NULL);
+	if (result->error != NULL)
+		e->add_str("error", result->error);
+
+	struct event *event = e->event();
+	if (db->debug_queries)
+		event_set_forced_debug(event, TRUE);
+	if (reply_usecs/1000 >= db->warn_timeout_msecs) {
+		db->counters[CASSANDRA_COUNTER_TYPE_QUERY_SLOW]++;
+		e_warning(event, "%s", str_c(str));
+	} else {
+		e_debug(event, "%s", str_c(str));
+	}
+}
+
+static void driver_cassandra_result_free(struct sql_result *_result)
+{
+	struct cassandra_db *db = (struct cassandra_db *)_result->db;
+	struct cassandra_result *result = (struct cassandra_result *)_result;
+	long long reply_usecs;
+
+	i_assert(!result->api.callback);
+	i_assert(result->callback == NULL);
+
+	if (_result == db->sync_result)
+		db->sync_result = NULL;
+
+	reply_usecs = timeval_diff_usecs(&result->finish_time,
+					 &result->start_time);
+	driver_cassandra_log_result(result, FALSE, reply_usecs);
+
+	if (result->page_num > 0 && !result->paging_continues) {
+		/* Multi-page query finishes now. Log a debug/warning summary
+		   message about it separate from the per-page messages. */
+		reply_usecs = timeval_diff_usecs(&result->finish_time,
+						 &result->page0_start_time);
+		driver_cassandra_log_result(result, TRUE, reply_usecs);
+	}
+
+	if (result->result != NULL)
+		cass_result_free(result->result);
+	if (result->iterator != NULL)
+		cass_iterator_free(result->iterator);
+	if (result->statement != NULL)
+		cass_statement_free(result->statement);
+	pool_unref(&result->row_pool);
+	event_unref(&result->api.event);
+	i_free(result->query);
+	i_free(result->error);
+	i_free(result);
+}
+
+static void result_finish(struct cassandra_result *result)
+{
+	struct cassandra_db *db = (struct cassandra_db *)result->api.db;
+	bool free_result = TRUE;
+
+	result->finished = TRUE;
+	result->finish_time = ioloop_timeval;
+	driver_cassandra_result_unlink(db, result);
+
+	i_assert((result->error != NULL) == (result->iterator == NULL));
+
+	result->api.callback = TRUE;
+	T_BEGIN {
+		result->callback(&result->api, result->context);
+	} T_END;
+	result->api.callback = FALSE;
+
+	free_result = db->sync_result != &result->api;
+	if (db->ioloop != NULL)
+		io_loop_stop(db->ioloop);
+
+	i_assert(!free_result || result->api.refcount > 0);
+	result->callback = NULL;
+	if (free_result)
+		sql_result_unref(&result->api);
+}
+
+static void query_resend_with_fallback(struct cassandra_result *result)
+{
+	struct cassandra_db *db = (struct cassandra_db *)result->api.db;
+	time_t last_warning =
+		ioloop_time - db->last_fallback_warning[result->query_type];
+
+	if (last_warning >= CASSANDRA_FALLBACK_WARN_INTERVAL_SECS) {
+		e_warning(db->api.event,
+			  "%s - retrying future %s queries with consistency %s (instead of %s)",
+			  result->error, cassandra_query_type_names[result->query_type],
+			  cass_consistency_string(result->fallback_consistency),
+			  cass_consistency_string(result->consistency));
+		db->last_fallback_warning[result->query_type] = ioloop_time;
+	}
+	i_free_and_null(result->error);
+	db->fallback_failures[result->query_type]++;
+
+	result->consistency = result->fallback_consistency;
+	driver_cassandra_result_send_query(result);
+}
+
+static void counters_inc_error(struct cassandra_db *db, CassError error)
+{
+	switch (error) {
+	case CASS_ERROR_LIB_NO_HOSTS_AVAILABLE:
+		db->counters[CASSANDRA_COUNTER_TYPE_QUERY_RECV_ERR_NO_HOSTS]++;
+		break;
+	case CASS_ERROR_LIB_REQUEST_QUEUE_FULL:
+		db->counters[CASSANDRA_COUNTER_TYPE_QUERY_RECV_ERR_QUEUE_FULL]++;
+		break;
+	case CASS_ERROR_LIB_REQUEST_TIMED_OUT:
+		db->counters[CASSANDRA_COUNTER_TYPE_QUERY_RECV_ERR_CLIENT_TIMEOUT]++;
+		break;
+	case CASS_ERROR_SERVER_WRITE_TIMEOUT:
+		db->counters[CASSANDRA_COUNTER_TYPE_QUERY_RECV_ERR_SERVER_TIMEOUT]++;
+		break;
+	case CASS_ERROR_SERVER_UNAVAILABLE:
+		db->counters[CASSANDRA_COUNTER_TYPE_QUERY_RECV_ERR_SERVER_UNAVAILABLE]++;
+		break;
+	default:
+		db->counters[CASSANDRA_COUNTER_TYPE_QUERY_RECV_ERR_OTHER]++;
+		break;
+	}
+}
+
+static bool query_error_want_fallback(CassError error)
+{
+	switch (error) {
+	case CASS_ERROR_LIB_WRITE_ERROR:
+	case CASS_ERROR_LIB_REQUEST_TIMED_OUT:
+		/* Communication problems on client side. Maybe it will work
+		   with fallback consistency? */
+		return TRUE;
+	case CASS_ERROR_LIB_NO_HOSTS_AVAILABLE:
+		/* The client library couldn't connect to enough Cassandra
+		   nodes. The error message text is the same as for
+		   CASS_ERROR_SERVER_UNAVAILABLE. */
+		return TRUE;
+	case CASS_ERROR_SERVER_SERVER_ERROR:
+	case CASS_ERROR_SERVER_OVERLOADED:
+	case CASS_ERROR_SERVER_IS_BOOTSTRAPPING:
+	case CASS_ERROR_SERVER_READ_TIMEOUT:
+	case CASS_ERROR_SERVER_READ_FAILURE:
+	case CASS_ERROR_SERVER_WRITE_FAILURE:
+		/* Servers are having trouble. Maybe with fallback consistency
+		   we can reach non-troubled servers? */
+		return TRUE;
+	case CASS_ERROR_SERVER_UNAVAILABLE:
+		/* Cassandra server knows that there aren't enough nodes
+		   available. "All hosts in current policy attempted and were
+		   either unavailable or failed". */
+		return TRUE;
+	case CASS_ERROR_SERVER_WRITE_TIMEOUT:
+		/* Cassandra server couldn't reach all the needed nodes.
+		   This may be because it hasn't yet detected that the servers
+		   are down, or because the servers are just too busy. We'll
+		   try the fallback consistency to avoid unnecessary temporary
+		   errors. */
+		return TRUE;
+	default:
+		return FALSE;
+	}
+}
+
+static enum sql_result_error_type
+driver_cassandra_error_is_uncertain(CassError error)
+{
+	switch (error) {
+	case CASS_ERROR_SERVER_WRITE_FAILURE:
+		/* This happens when some of the replicas that were contacted
+		 * by the coordinator replied with an error. */
+	case CASS_ERROR_SERVER_WRITE_TIMEOUT:
+		/* A Cassandra timeout during a write query. */
+	case CASS_ERROR_SERVER_UNAVAILABLE:
+		/* The coordinator knows there are not enough replicas alive
+		 * to perform a query with the requested consistency level. */
+	case CASS_ERROR_LIB_REQUEST_TIMED_OUT:
+		/* A request sent from the driver has timed out. */
+	case CASS_ERROR_LIB_WRITE_ERROR:
+		/* A write error occured. */
+		return SQL_RESULT_ERROR_TYPE_WRITE_UNCERTAIN;
+	default:
+		return SQL_RESULT_ERROR_TYPE_UNKNOWN;
+	}
+}
+
+static void query_callback(CassFuture *future, void *context)
+{
+	struct cassandra_result *result = context;
+	struct cassandra_db *db = (struct cassandra_db *)result->api.db;
+	CassError error = cass_future_error_code(future);
+
+	if (error != CASS_OK) {
+		const char *errmsg;
+		size_t errsize;
+		int msecs;
+
+		cass_future_error_message(future, &errmsg, &errsize);
+		i_free(result->error);
+
+		msecs = timeval_diff_msecs(&ioloop_timeval, &result->start_time);
+		counters_inc_error(db, error);
+		/* Timeouts bring uncertainty whether the query succeeded or
+		   not. Also _SERVER_UNAVAILABLE could have actually written
+		   enough copies of the data for the query to succeed. */
+		result->api.error_type = driver_cassandra_error_is_uncertain(error);
+		result->error = i_strdup_printf(
+			"Query '%s' failed: %.*s (in %u.%03u secs%s)",
+			result->query, (int)errsize, errmsg, msecs/1000, msecs%1000,
+			result->page_num == 0 ?
+				"" :
+				t_strdup_printf(", page %u", result->page_num));
+
+		if (query_error_want_fallback(error) &&
+		    result->fallback_consistency != result->consistency) {
+			/* retry with fallback consistency */
+			query_resend_with_fallback(result);
+			return;
+		}
+		result_finish(result);
+		return;
+	}
+	db->counters[CASSANDRA_COUNTER_TYPE_QUERY_RECV_OK]++;
+
+	if (result->fallback_consistency != result->consistency) {
+		/* non-fallback query finished successfully. if there had been
+		   any fallbacks, reset them. */
+		db->fallback_failures[result->query_type] = 0;
+	}
+
+	result->result = cass_future_get_result(future);
+	result->iterator = cass_iterator_from_result(result->result);
+	result_finish(result);
+}
+
+static void driver_cassandra_init_statement(struct cassandra_result *result)
+{
+	struct cassandra_db *db = (struct cassandra_db *)result->api.db;
+
+	cass_statement_set_consistency(result->statement, result->consistency);
+
+#ifdef HAVE_CASSANDRA_SPECULATIVE_POLICY
+	cass_statement_set_is_idempotent(result->statement, cass_true);
+#endif
+	if (db->page_size > 0)
+		cass_statement_set_paging_size(result->statement, db->page_size);
+}
+
+static void driver_cassandra_result_send_query(struct cassandra_result *result)
+{
+	struct cassandra_db *db = (struct cassandra_db *)result->api.db;
+	CassFuture *future;
+
+	i_assert(result->statement != NULL);
+
+	db->counters[CASSANDRA_COUNTER_TYPE_QUERY_SENT]++;
+	if (result->query_type != CASSANDRA_QUERY_TYPE_READ_MORE)
+		driver_cassandra_init_statement(result);
+
+	future = cass_session_execute(db->session, result->statement);
+	driver_cassandra_set_callback(future, db, query_callback, result);
+}
+
+static bool
+driver_cassandra_want_fallback_query(struct cassandra_result *result)
+{
+	struct cassandra_db *db = (struct cassandra_db *)result->api.db;
+	unsigned int failure_count = db->fallback_failures[result->query_type];
+	unsigned int i, msecs = CASSANDRA_FALLBACK_FIRST_RETRY_MSECS;
+	struct timeval tv;
+
+	if (failure_count == 0)
+		return FALSE;
+	/* double the retries every time. */
+	for (i = 1; i < failure_count; i++) {
+		msecs *= 2;
+		if (msecs >= CASSANDRA_FALLBACK_MAX_RETRY_MSECS) {
+			msecs = CASSANDRA_FALLBACK_MAX_RETRY_MSECS;
+			break;
+		}
+	}
+	/* If last primary query sent timestamp + msecs is older than current
+	   time, we need to retry the primary query. Note that this practically
+	   prevents multiple primary queries from being attempted
+	   simultaneously, because the caller updates primary_query_last_sent
+	   immediately when returning.
+
+	   The only time when multiple primary queries can be running in
+	   parallel is when the earlier query is being slow and hasn't finished
+	   early enough. This could even be a wanted feature, since while the
+	   first query might have to wait for a timeout, Cassandra could have
+	   been fixed in the meantime and the second query finishes
+	   successfully. */
+	tv = db->primary_query_last_sent[result->query_type];
+	timeval_add_msecs(&tv, msecs);
+	return timeval_cmp(&ioloop_timeval, &tv) < 0;
+}
+
+static int driver_cassandra_send_query(struct cassandra_result *result)
+{
+	struct cassandra_db *db = (struct cassandra_db *)result->api.db;
+	int ret;
+
+	if (!SQL_DB_IS_READY(&db->api)) {
+		if ((ret = sql_connect(&db->api)) <= 0) {
+			if (ret < 0)
+				driver_cassandra_close(db,
+					"Couldn't connect to Cassandra");
+			return ret;
+		}
+	}
+
+	if (result->page0_start_time.tv_sec == 0)
+		result->page0_start_time = ioloop_timeval;
+	result->start_time = ioloop_timeval;
+	result->row_pool = pool_alloconly_create("cassandra result", 512);
+	switch (result->query_type) {
+	case CASSANDRA_QUERY_TYPE_READ:
+		result->consistency = db->read_consistency;
+		result->fallback_consistency = db->read_fallback_consistency;
+		break;
+	case CASSANDRA_QUERY_TYPE_READ_MORE:
+		/* consistency is already set and we don't want to fallback
+		   at this point anymore. */
+		result->fallback_consistency = result->consistency;
+		break;
+	case CASSANDRA_QUERY_TYPE_WRITE:
+		result->consistency = db->write_consistency;
+		result->fallback_consistency = db->write_fallback_consistency;
+		break;
+	case CASSANDRA_QUERY_TYPE_DELETE:
+		result->consistency = db->delete_consistency;
+		result->fallback_consistency = db->delete_fallback_consistency;
+		break;
+	case CASSANDRA_QUERY_TYPE_COUNT:
+		i_unreached();
+	}
+
+	if (driver_cassandra_want_fallback_query(result))
+		result->consistency = result->fallback_consistency;
+	else
+		db->primary_query_last_sent[result->query_type] = ioloop_timeval;
+
+	driver_cassandra_result_send_query(result);
+	result->query_sent = TRUE;
+	return 1;
+}
+
+static void driver_cassandra_send_queries(struct cassandra_db *db)
+{
+	struct cassandra_result *const *results;
+	unsigned int i, count;
+
+	results = array_get(&db->results, &count);
+	for (i = 0; i < count; i++) {
+		if (!results[i]->query_sent && results[i]->statement != NULL) {
+			if (driver_cassandra_send_query(results[i]) <= 0)
+				break;
+		}
+	}
+}
+
+static void exec_callback(struct sql_result *_result ATTR_UNUSED,
+			  void *context ATTR_UNUSED)
+{
+}
+
+static struct cassandra_result *
+driver_cassandra_query_init(struct cassandra_db *db, const char *query,
+			    enum cassandra_query_type query_type,
+			    bool is_prepared,
+			    sql_query_callback_t *callback, void *context)
+{
+	struct cassandra_result *result;
+
+	result = i_new(struct cassandra_result, 1);
+	result->api = driver_cassandra_result;
+	result->api.db = &db->api;
+	result->api.refcount = 1;
+	result->callback = callback;
+	result->context = context;
+	result->query_type = query_type;
+	result->query = i_strdup(query);
+	result->is_prepared = is_prepared;
+	result->api.event = event_create(db->api.event);
+	array_push_back(&db->results, &result);
+	return result;
+}
+
+static void
+driver_cassandra_query_full(struct sql_db *_db, const char *query,
+			    enum cassandra_query_type query_type,
+			    sql_query_callback_t *callback, void *context)
+{
+	struct cassandra_db *db = (struct cassandra_db *)_db;
+	struct cassandra_result *result;
+
+	result = driver_cassandra_query_init(db, query, query_type, FALSE,
+					     callback, context);
+	result->statement = cass_statement_new(query, 0);
+	(void)driver_cassandra_send_query(result);
+}
+
+static void driver_cassandra_exec(struct sql_db *db, const char *query)
+{
+	driver_cassandra_query_full(db, query, CASSANDRA_QUERY_TYPE_WRITE,
+				    exec_callback, NULL);
+}
+
+static void driver_cassandra_query(struct sql_db *db, const char *query,
+				   sql_query_callback_t *callback, void *context)
+{
+	driver_cassandra_query_full(db, query, CASSANDRA_QUERY_TYPE_READ,
+				    callback, context);
+}
+
+static void cassandra_query_s_callback(struct sql_result *result, void *context)
+{
+	struct cassandra_db *db = context;
+
+	db->sync_result = result;
+}
+
+static void driver_cassandra_sync_init(struct cassandra_db *db)
+{
+	if (sql_connect(&db->api) < 0)
+		return;
+	db->orig_ioloop = current_ioloop;
+	db->ioloop = io_loop_create();
+	if (IS_CONNECTED(db))
+		return;
+	i_assert(db->api.state == SQL_DB_STATE_CONNECTING);
+
+	db->io_pipe = io_loop_move_io(&db->io_pipe);
+	/* wait for connecting to finish */
+	io_loop_run(db->ioloop);
+}
+
+static void driver_cassandra_sync_deinit(struct cassandra_db *db)
+{
+	if (db->orig_ioloop == NULL)
+		return;
+	if (db->io_pipe != NULL) {
+		io_loop_set_current(db->orig_ioloop);
+		db->io_pipe = io_loop_move_io(&db->io_pipe);
+		io_loop_set_current(db->ioloop);
+	}
+	io_loop_destroy(&db->ioloop);
+}
+
+static struct sql_result *
+driver_cassandra_sync_query(struct cassandra_db *db, const char *query,
+			    enum cassandra_query_type query_type)
+{
+	struct sql_result *result;
+
+	i_assert(db->sync_result == NULL);
+
+	switch (db->api.state) {
+	case SQL_DB_STATE_CONNECTING:
+	case SQL_DB_STATE_BUSY:
+		i_unreached();
+	case SQL_DB_STATE_DISCONNECTED:
+		sql_not_connected_result.refcount++;
+		return &sql_not_connected_result;
+	case SQL_DB_STATE_IDLE:
+		break;
+	}
+
+	driver_cassandra_query_full(&db->api, query, query_type,
+				    cassandra_query_s_callback, db);
+	if (db->sync_result == NULL) {
+		db->io_pipe = io_loop_move_io(&db->io_pipe);
+		io_loop_run(db->ioloop);
+	}
+
+	result = db->sync_result;
+	if (result == &sql_not_connected_result) {
+		/* we don't end up in cassandra's free function, so sync_result
+		   won't be set to NULL if we don't do it here. */
+		db->sync_result = NULL;
+	} else if (result == NULL) {
+		result = &sql_not_connected_result;
+		result->refcount++;
+	}
+	return result;
+}
+
+static struct sql_result *
+driver_cassandra_query_s(struct sql_db *_db, const char *query)
+{
+	struct cassandra_db *db = (struct cassandra_db *)_db;
+	struct sql_result *result;
+
+	driver_cassandra_sync_init(db);
+	result = driver_cassandra_sync_query(db, query,
+					     CASSANDRA_QUERY_TYPE_READ);
+	driver_cassandra_sync_deinit(db);
+	return result;
+}
+
+static int
+driver_cassandra_get_value(struct cassandra_result *result,
+			   const CassValue *value, const char **str_r,
+			   size_t *len_r)
+{
+	const unsigned char *output;
+	void *output_dup;
+	size_t output_size;
+	CassError rc;
+	const char *type;
+
+	if (cass_value_is_null(value) != 0) {
+		*str_r = NULL;
+		*len_r = 0;
+		return 0;
+	}
+
+	switch (cass_data_type_type(cass_value_data_type(value))) {
+	case CASS_VALUE_TYPE_INT: {
+		cass_int32_t num;
+
+		rc = cass_value_get_int32(value, &num);
+		if (rc == CASS_OK) {
+			const char *str = t_strdup_printf("%d", num);
+			output_size = strlen(str);
+			output = (const void *)str;
+		}
+		type = "int32";
+		break;
+	}
+	case CASS_VALUE_TYPE_TIMESTAMP:
+	case CASS_VALUE_TYPE_BIGINT: {
+		cass_int64_t num;
+
+		rc = cass_value_get_int64(value, &num);
+		if (rc == CASS_OK) {
+			const char *str = t_strdup_printf("%lld", (long long)num);
+			output_size = strlen(str);
+			output = (const void *)str;
+		}
+		type = "int64";
+		break;
+	}
+	default:
+		rc = cass_value_get_bytes(value, &output, &output_size);
+		type = "bytes";
+		break;
+	}
+	if (rc != CASS_OK) {
+		i_free(result->error);
+		result->error = i_strdup_printf("Couldn't get value as %s: %s",
+						type, cass_error_desc(rc));
+		return -1;
+	}
+	output_dup = p_malloc(result->row_pool, output_size + 1);
+	memcpy(output_dup, output, output_size);
+	*str_r = output_dup;
+	*len_r = output_size;
+	return 0;
+}
+
+static int driver_cassandra_result_next_page(struct cassandra_result *result)
+{
+	struct cassandra_db *db = (struct cassandra_db *)result->api.db;
+
+	if (db->page_size == 0) {
+		/* no paging */
+		return 0;
+	}
+	if (cass_result_has_more_pages(result->result) == cass_false)
+		return 0;
+
+	/* callers that don't support sql_query_more() will still get a useful
+	   error message. */
+	i_free(result->error);
+	result->error = i_strdup(
+		"Paged query has more results, but not supported by the caller");
+	return SQL_RESULT_NEXT_MORE;
+}
+
+static int driver_cassandra_result_next_row(struct sql_result *_result)
+{
+	struct cassandra_result *result = (struct cassandra_result *)_result;
+	const CassRow *row;
+	const CassValue *value;
+	const char *str;
+	size_t size;
+	unsigned int i;
+	int ret = 1;
+
+	if (result->iterator == NULL)
+		return -1;
+
+	if (cass_iterator_next(result->iterator) == 0)
+		return driver_cassandra_result_next_page(result);
+	result->row_count++;
+	result->total_row_count++;
+
+	p_clear(result->row_pool);
+	p_array_init(&result->fields, result->row_pool, 8);
+	p_array_init(&result->field_sizes, result->row_pool, 8);
+
+	row = cass_iterator_get_row(result->iterator);
+	for (i = 0; (value = cass_row_get_column(row, i)) != NULL; i++) {
+		if (driver_cassandra_get_value(result, value, &str, &size) < 0) {
+			ret = -1;
+			break;
+		}
+		array_push_back(&result->fields, &str);
+		array_push_back(&result->field_sizes, &size);
+	}
+	return ret;
+}
+
+static void
+driver_cassandra_result_more(struct sql_result **_result, bool async,
+			     sql_query_callback_t *callback, void *context)
+{
+	struct cassandra_db *db = (struct cassandra_db *)(*_result)->db;
+	struct cassandra_result *new_result;
+	struct cassandra_result *old_result =
+		(struct cassandra_result *)*_result;
+
+	/* Initialize the next page as a new sql_result */
+	new_result = driver_cassandra_query_init(db, old_result->query,
+						 CASSANDRA_QUERY_TYPE_READ_MORE,
+						 old_result->is_prepared,
+						 callback, context);
+
+	/* Preserve the statement and update its paging state */
+	new_result->statement = old_result->statement;
+	old_result->statement = NULL;
+	cass_statement_set_paging_state(new_result->statement,
+					old_result->result);
+	old_result->paging_continues = TRUE;
+	/* The caller did support paging. Clear out the "...not supported by
+	   the caller" error text, so it won't be in the debug log output. */
+	i_free_and_null(old_result->error);
+
+	new_result->timestamp = old_result->timestamp;
+	new_result->consistency = old_result->consistency;
+	new_result->page_num = old_result->page_num + 1;
+	new_result->page0_start_time = old_result->page0_start_time;
+	new_result->total_row_count = old_result->total_row_count;
+
+	sql_result_unref(*_result);
+	*_result = NULL;
+
+	if (async)
+		(void)driver_cassandra_send_query(new_result);
+	else {
+		i_assert(db->api.state == SQL_DB_STATE_IDLE);
+		driver_cassandra_sync_init(db);
+		(void)driver_cassandra_send_query(new_result);
+		if (new_result->result == NULL) {
+			db->io_pipe = io_loop_move_io(&db->io_pipe);
+			io_loop_run(db->ioloop);
+		}
+		driver_cassandra_sync_deinit(db);
+
+		callback(&new_result->api, context);
+	}
+}
+
+static unsigned int
+driver_cassandra_result_get_fields_count(struct sql_result *_result)
+{
+	struct cassandra_result *result = (struct cassandra_result *)_result;
+
+	return array_count(&result->fields);
+}
+
+static const char *
+driver_cassandra_result_get_field_name(struct sql_result *_result ATTR_UNUSED,
+				       unsigned int idx ATTR_UNUSED)
+{
+	i_unreached();
+}
+
+static int
+driver_cassandra_result_find_field(struct sql_result *_result ATTR_UNUSED,
+				   const char *field_name ATTR_UNUSED)
+{
+	i_unreached();
+}
+
+static const char *
+driver_cassandra_result_get_field_value(struct sql_result *_result,
+					unsigned int idx)
+{
+	struct cassandra_result *result = (struct cassandra_result *)_result;
+
+	return array_idx_elem(&result->fields, idx);
+}
+
+static const unsigned char *
+driver_cassandra_result_get_field_value_binary(struct sql_result *_result ATTR_UNUSED,
+					       unsigned int idx ATTR_UNUSED,
+					       size_t *size_r ATTR_UNUSED)
+{
+	struct cassandra_result *result = (struct cassandra_result *)_result;
+	const char *str;
+	const size_t *sizep;
+
+	str = array_idx_elem(&result->fields, idx);
+	sizep = array_idx(&result->field_sizes, idx);
+	*size_r = *sizep;
+	return (const void *)str;
+}
+
+static const char *
+driver_cassandra_result_find_field_value(struct sql_result *result ATTR_UNUSED,
+					 const char *field_name ATTR_UNUSED)
+{
+	i_unreached();
+}
+
+static const char *const *
+driver_cassandra_result_get_values(struct sql_result *_result)
+{
+	struct cassandra_result *result = (struct cassandra_result *)_result;
+
+	return array_front(&result->fields);
+}
+
+static const char *driver_cassandra_result_get_error(struct sql_result *_result)
+{
+	struct cassandra_result *result = (struct cassandra_result *)_result;
+
+	if (result->error != NULL)
+		return result->error;
+	return "FIXME";
+}
+
+static struct sql_transaction_context *
+driver_cassandra_transaction_begin(struct sql_db *db)
+{
+	struct cassandra_transaction_context *ctx;
+
+	ctx = i_new(struct cassandra_transaction_context, 1);
+	ctx->ctx.db = db;
+	ctx->ctx.event = event_create(db->event);
+	ctx->refcount = 1;
+	return &ctx->ctx;
+}
+
+static void
+driver_cassandra_transaction_unref(struct cassandra_transaction_context **_ctx)
+{
+	struct cassandra_transaction_context *ctx = *_ctx;
+
+	*_ctx = NULL;
+	i_assert(ctx->refcount > 0);
+	if (--ctx->refcount > 0)
+		return;
+
+	event_unref(&ctx->ctx.event);
+	i_free(ctx->query);
+	i_free(ctx->error);
+	i_free(ctx);
+}
+
+static void
+transaction_set_failed(struct cassandra_transaction_context *ctx,
+		       const char *error)
+{
+	if (ctx->failed) {
+		i_assert(ctx->error != NULL);
+	} else {
+		i_assert(ctx->error == NULL);
+		ctx->failed = TRUE;
+		ctx->error = i_strdup(error);
+	}
+}
+
+static void
+transaction_commit_callback(struct sql_result *result, void *context)
+{
+	struct cassandra_transaction_context *ctx = context;
+	struct sql_commit_result commit_result;
+
+	i_zero(&commit_result);
+	if (sql_result_next_row(result) < 0) {
+		commit_result.error = sql_result_get_error(result);
+		commit_result.error_type = sql_result_get_error_type(result);
+		e_debug(sql_transaction_finished_event(&ctx->ctx)->
+			add_str("error", commit_result.error)->event(),
+			"Transaction failed");
+	} else {
+		e_debug(sql_transaction_finished_event(&ctx->ctx)->event(),
+			"Transaction committed");
+	}
+	ctx->callback(&commit_result, ctx->context);
+	driver_cassandra_transaction_unref(&ctx);
+}
+
+static void
+driver_cassandra_transaction_commit(struct sql_transaction_context *_ctx,
+				    sql_commit_callback_t *callback, void *context)
+{
+	struct cassandra_transaction_context *ctx =
+		(struct cassandra_transaction_context *)_ctx;
+	struct cassandra_db *db = (struct cassandra_db *)_ctx->db;
+	enum cassandra_query_type query_type;
+	struct sql_commit_result result;
+
+	i_zero(&result);
+	ctx->callback = callback;
+	ctx->context = context;
+
+	if (ctx->failed || (ctx->query == NULL && ctx->stmt == NULL)) {
+		if (ctx->failed)
+			result.error = ctx->error;
+
+		e_debug(sql_transaction_finished_event(_ctx)->
+			add_str("error", "Rolled back")->event(),
+			"Transaction rolled back");
+		callback(&result, context);
+		driver_cassandra_transaction_unref(&ctx);
+		return;
+	}
+
+	/* just a single query, send it */
+	const char *query = ctx->query != NULL ?
+		ctx->query : sql_statement_get_query(&ctx->stmt->stmt);
+	if (strncasecmp(query, "DELETE ", 7) == 0)
+		query_type = CASSANDRA_QUERY_TYPE_DELETE;
+	else
+		query_type = CASSANDRA_QUERY_TYPE_WRITE;
+
+	if (ctx->query != NULL) {
+		struct cassandra_result *cass_result;
+
+		cass_result = driver_cassandra_query_init(db, query, query_type,
+			FALSE, transaction_commit_callback, ctx);
+		cass_result->statement = cass_statement_new(query, 0);
+		if (ctx->query_timestamp != 0) {
+			cass_result->timestamp = ctx->query_timestamp;
+			cass_statement_set_timestamp(cass_result->statement,
+						     ctx->query_timestamp);
+		}
+		(void)driver_cassandra_send_query(cass_result);
+	} else {
+		ctx->stmt->result =
+			driver_cassandra_query_init(db, query, query_type, TRUE,
+				transaction_commit_callback, ctx);
+		if (ctx->stmt->cass_stmt == NULL) {
+			/* wait for prepare to finish */
+		} else {
+			ctx->stmt->result->statement = ctx->stmt->cass_stmt;
+			ctx->stmt->result->timestamp = ctx->stmt->timestamp;
+			(void)driver_cassandra_send_query(ctx->stmt->result);
+			pool_unref(&ctx->stmt->stmt.pool);
+		}
+	}
+}
+
+static void
+driver_cassandra_try_commit_s(struct cassandra_transaction_context *ctx)
+{
+	struct sql_transaction_context *_ctx = &ctx->ctx;
+	struct cassandra_db *db = (struct cassandra_db *)_ctx->db;
+	struct sql_result *result = NULL;
+	enum cassandra_query_type query_type;
+
+	/* just a single query, send it */
+	if (strncasecmp(ctx->query, "DELETE ", 7) == 0)
+		query_type = CASSANDRA_QUERY_TYPE_DELETE;
+	else
+		query_type = CASSANDRA_QUERY_TYPE_WRITE;
+	driver_cassandra_sync_init(db);
+	result = driver_cassandra_sync_query(db, ctx->query, query_type);
+	driver_cassandra_sync_deinit(db);
+
+	if (sql_result_next_row(result) < 0)
+		transaction_set_failed(ctx, sql_result_get_error(result));
+	sql_result_unref(result);
+}
+
+static int
+driver_cassandra_transaction_commit_s(struct sql_transaction_context *_ctx,
+				      const char **error_r)
+{
+	struct cassandra_transaction_context *ctx =
+		(struct cassandra_transaction_context *)_ctx;
+
+	if (ctx->stmt != NULL) {
+		/* nothing should be using this - don't bother implementing */
+		i_panic("cassandra: sql_transaction_commit_s() not supported for prepared statements");
+	}
+
+	if (ctx->query != NULL && !ctx->failed)
+		driver_cassandra_try_commit_s(ctx);
+	*error_r = t_strdup(ctx->error);
+
+	i_assert(ctx->refcount == 1);
+	i_assert((*error_r != NULL) == ctx->failed);
+	driver_cassandra_transaction_unref(&ctx);
+	return *error_r == NULL ? 0 : -1;
+}
+
+static void
+driver_cassandra_transaction_rollback(struct sql_transaction_context *_ctx)
+{
+	struct cassandra_transaction_context *ctx =
+		(struct cassandra_transaction_context *)_ctx;
+
+	i_assert(ctx->refcount == 1);
+	driver_cassandra_transaction_unref(&ctx);
+}
+
+static void
+driver_cassandra_update(struct sql_transaction_context *_ctx, const char *query,
+			unsigned int *affected_rows)
+{
+	struct cassandra_transaction_context *ctx =
+		(struct cassandra_transaction_context *)_ctx;
+
+	i_assert(affected_rows == NULL);
+
+	if (ctx->query != NULL || ctx->stmt != NULL) {
+		transaction_set_failed(ctx, "Multiple changes in transaction not supported");
+		return;
+	}
+	ctx->query = i_strdup(query);
+}
+
+static const char *
+driver_cassandra_escape_blob(struct sql_db *_db ATTR_UNUSED,
+			     const unsigned char *data, size_t size)
+{
+	string_t *str = t_str_new(128);
+
+	str_append(str, "0x");
+	binary_to_hex_append(str, data, size);
+	return str_c(str);
+}
+
+static CassError
+driver_cassandra_bind_int(struct cassandra_sql_statement *stmt,
+			  unsigned int column_idx, int64_t value)
+{
+	const CassDataType *data_type;
+	CassValueType value_type;
+
+	i_assert(stmt->prep != NULL);
+
+	/* statements require exactly correct value type */
+	data_type = cass_prepared_parameter_data_type(stmt->prep->prepared,
+						      column_idx);
+	value_type = cass_data_type_type(data_type);
+
+	switch (value_type) {
+	case CASS_VALUE_TYPE_INT:
+		if (value < INT32_MIN || value > INT32_MAX)
+			return CASS_ERROR_LIB_INVALID_VALUE_TYPE;
+		return cass_statement_bind_int32(stmt->cass_stmt, column_idx,
+						 value);
+	case CASS_VALUE_TYPE_TIMESTAMP:
+	case CASS_VALUE_TYPE_BIGINT:
+		return cass_statement_bind_int64(stmt->cass_stmt, column_idx,
+						 value);
+	case CASS_VALUE_TYPE_SMALL_INT:
+		if (value < INT16_MIN || value > INT16_MAX)
+			return CASS_ERROR_LIB_INVALID_VALUE_TYPE;
+		return cass_statement_bind_int16(stmt->cass_stmt, column_idx,
+						 value);
+	case CASS_VALUE_TYPE_TINY_INT:
+		if (value < INT8_MIN || value > INT8_MAX)
+			return CASS_ERROR_LIB_INVALID_VALUE_TYPE;
+		return cass_statement_bind_int8(stmt->cass_stmt, column_idx,
+						value);
+	default:
+		return CASS_ERROR_LIB_INVALID_VALUE_TYPE;
+	}
+}
+
+static void prepare_finish_arg(struct cassandra_sql_statement *stmt,
+			       const struct cassandra_sql_arg *arg)
+{
+	CassError rc;
+
+	if (arg->value_str != NULL) {
+		rc = cass_statement_bind_string(stmt->cass_stmt, arg->column_idx,
+						arg->value_str);
+	} else if (arg->value_binary != NULL) {
+		rc = cass_statement_bind_bytes(stmt->cass_stmt, arg->column_idx,
+					       arg->value_binary,
+					       arg->value_binary_size);
+	} else {
+		rc = driver_cassandra_bind_int(stmt, arg->column_idx,
+					       arg->value_int64);
+	}
+	if (rc != CASS_OK) {
+		e_error(stmt->stmt.db->event,
+			"Statement '%s': Failed to bind column %u: %s",
+			stmt->stmt.query_template, arg->column_idx,
+			cass_error_desc(rc));
+	}
+}
+
+static void prepare_finish_statement(struct cassandra_sql_statement *stmt)
+{
+	const struct cassandra_sql_arg *arg;
+
+	if (stmt->prep->prepared == NULL) {
+		i_assert(stmt->prep->error != NULL);
+
+		if (stmt->result != NULL) {
+			stmt->result->error = i_strdup(stmt->prep->error);
+			result_finish(stmt->result);
+		}
+		pool_unref(&stmt->stmt.pool);
+		return;
+	}
+	stmt->cass_stmt = cass_prepared_bind(stmt->prep->prepared);
+
+	if (stmt->timestamp != 0)
+		cass_statement_set_timestamp(stmt->cass_stmt, stmt->timestamp);
+
+	if (array_is_created(&stmt->pending_args)) {
+		array_foreach(&stmt->pending_args, arg)
+			prepare_finish_arg(stmt, arg);
+	}
+	if (stmt->result != NULL) {
+		stmt->result->statement = stmt->cass_stmt;
+		stmt->result->timestamp = stmt->timestamp;
+		(void)driver_cassandra_send_query(stmt->result);
+		pool_unref(&stmt->stmt.pool);
+	}
+}
+
+static void
+prepare_finish_pending_statements(struct cassandra_sql_prepared_statement *prep_stmt)
+{
+	struct cassandra_sql_statement *stmt;
+
+	array_foreach_elem(&prep_stmt->pending_statements, stmt)
+		prepare_finish_statement(stmt);
+	array_clear(&prep_stmt->pending_statements);
+}
+
+static void prepare_callback(CassFuture *future, void *context)
+{
+	struct cassandra_sql_prepared_statement *prep_stmt = context;
+	CassError error = cass_future_error_code(future);
+
+	if (error != CASS_OK) {
+		const char *errmsg;
+		size_t errsize;
+
+		cass_future_error_message(future, &errmsg, &errsize);
+		i_free(prep_stmt->error);
+		prep_stmt->error = i_strndup(errmsg, errsize);
+	} else {
+		prep_stmt->prepared = cass_future_get_prepared(future);
+	}
+
+	prepare_finish_pending_statements(prep_stmt);
+}
+
+static void prepare_start(struct cassandra_sql_prepared_statement *prep_stmt)
+{
+	struct cassandra_db *db = (struct cassandra_db *)prep_stmt->prep_stmt.db;
+	CassFuture *future;
+
+	if (!SQL_DB_IS_READY(&db->api)) {
+		if (!prep_stmt->pending) {
+			prep_stmt->pending = TRUE;
+			array_push_back(&db->pending_prepares, &prep_stmt);
+
+			if (sql_connect(&db->api) < 0)
+				i_unreached();
+		}
+		return;
+	}
+
+	/* clear the current error in case we're retrying */
+	i_free_and_null(prep_stmt->error);
+
+	future = cass_session_prepare(db->session,
+				      prep_stmt->prep_stmt.query_template);
+	driver_cassandra_set_callback(future, db, prepare_callback, prep_stmt);
+}
+
+static void driver_cassandra_prepare_pending(struct cassandra_db *db)
+{
+	struct cassandra_sql_prepared_statement *prep_stmt;
+
+	i_assert(SQL_DB_IS_READY(&db->api));
+
+	array_foreach_elem(&db->pending_prepares, prep_stmt) {
+		prep_stmt->pending = FALSE;
+		prepare_start(prep_stmt);
+	}
+	array_clear(&db->pending_prepares);
+}
+
+static struct sql_prepared_statement *
+driver_cassandra_prepared_statement_init(struct sql_db *db,
+					 const char *query_template)
+{
+	struct cassandra_sql_prepared_statement *prep_stmt =
+		i_new(struct cassandra_sql_prepared_statement, 1);
+	prep_stmt->prep_stmt.db = db;
+	prep_stmt->prep_stmt.refcount = 1;
+	prep_stmt->prep_stmt.query_template = i_strdup(query_template);
+	i_array_init(&prep_stmt->pending_statements, 4);
+	prepare_start(prep_stmt);
+	return &prep_stmt->prep_stmt;
+}
+
+static void
+driver_cassandra_prepared_statement_deinit(struct sql_prepared_statement *_prep_stmt)
+{
+	struct cassandra_sql_prepared_statement *prep_stmt =
+		(struct cassandra_sql_prepared_statement *)_prep_stmt;
+
+	i_assert(array_count(&prep_stmt->pending_statements) == 0);
+	if (prep_stmt->prepared != NULL)
+		cass_prepared_free(prep_stmt->prepared);
+	array_free(&prep_stmt->pending_statements);
+	i_free(prep_stmt->error);
+	i_free(prep_stmt->prep_stmt.query_template);
+	i_free(prep_stmt);
+}
+
+static struct sql_statement *
+driver_cassandra_statement_init(struct sql_db *db ATTR_UNUSED,
+				const char *query_template ATTR_UNUSED)
+{
+	pool_t pool = pool_alloconly_create("cassandra sql statement", 1024);
+	struct cassandra_sql_statement *stmt =
+		p_new(pool, struct cassandra_sql_statement, 1);
+	stmt->stmt.pool = pool;
+	return &stmt->stmt;
+}
+
+static struct sql_statement *
+driver_cassandra_statement_init_prepared(struct sql_prepared_statement *_prep_stmt)
+{
+	struct cassandra_sql_prepared_statement *prep_stmt =
+		(struct cassandra_sql_prepared_statement *)_prep_stmt;
+	pool_t pool = pool_alloconly_create("cassandra prepared sql statement", 1024);
+	struct cassandra_sql_statement *stmt =
+		p_new(pool, struct cassandra_sql_statement, 1);
+
+	stmt->stmt.pool = pool;
+	stmt->stmt.query_template =
+		p_strdup(stmt->stmt.pool, prep_stmt->prep_stmt.query_template);
+	stmt->prep = prep_stmt;
+
+	if (prep_stmt->prepared != NULL) {
+		/* statement is already prepared. we can use it immediately. */
+		stmt->cass_stmt = cass_prepared_bind(prep_stmt->prepared);
+	} else {
+		if (prep_stmt->error != NULL)
+			prepare_start(prep_stmt);
+		/* need to wait until prepare is finished */
+		array_push_back(&prep_stmt->pending_statements, &stmt);
+	}
+	return &stmt->stmt;
+}
+
+static void
+driver_cassandra_statement_abort(struct sql_statement *_stmt)
+{
+	struct cassandra_sql_statement *stmt =
+		(struct cassandra_sql_statement *)_stmt;
+
+	if (stmt->cass_stmt != NULL)
+		cass_statement_free(stmt->cass_stmt);
+}
+
+static void
+driver_cassandra_statement_set_timestamp(struct sql_statement *_stmt,
+					 const struct timespec *ts)
+{
+	struct cassandra_sql_statement *stmt =
+		(struct cassandra_sql_statement *)_stmt;
+	cass_int64_t ts_usecs =
+		(cass_int64_t)ts->tv_sec * 1000000ULL +
+		ts->tv_nsec / 1000;
+
+	i_assert(stmt->result == NULL);
+
+	if (stmt->cass_stmt != NULL)
+		cass_statement_set_timestamp(stmt->cass_stmt, ts_usecs);
+	stmt->timestamp = ts_usecs;
+}
+
+static struct cassandra_sql_arg *
+driver_cassandra_add_pending_arg(struct cassandra_sql_statement *stmt,
+				 unsigned int column_idx)
+{
+	struct cassandra_sql_arg *arg;
+
+	if (!array_is_created(&stmt->pending_args))
+		p_array_init(&stmt->pending_args, stmt->stmt.pool, 8);
+	arg = array_append_space(&stmt->pending_args);
+	arg->column_idx = column_idx;
+	return arg;
+}
+
+static void
+driver_cassandra_statement_bind_str(struct sql_statement *_stmt,
+				    unsigned int column_idx,
+				    const char *value)
+{
+	struct cassandra_sql_statement *stmt =
+		(struct cassandra_sql_statement *)_stmt;
+	if (stmt->cass_stmt != NULL)
+		cass_statement_bind_string(stmt->cass_stmt, column_idx, value);
+	else if (stmt->prep != NULL) {
+		struct cassandra_sql_arg *arg =
+			driver_cassandra_add_pending_arg(stmt, column_idx);
+		arg->value_str = p_strdup(_stmt->pool, value);
+	}
+}
+
+static void
+driver_cassandra_statement_bind_binary(struct sql_statement *_stmt,
+				       unsigned int column_idx,
+				       const void *value, size_t value_size)
+{
+	struct cassandra_sql_statement *stmt =
+		(struct cassandra_sql_statement *)_stmt;
+
+	if (stmt->cass_stmt != NULL) {
+		cass_statement_bind_bytes(stmt->cass_stmt, column_idx,
+					  value, value_size);
+	} else if (stmt->prep != NULL) {
+		struct cassandra_sql_arg *arg =
+			driver_cassandra_add_pending_arg(stmt, column_idx);
+		arg->value_binary = value_size == 0 ? &uchar_nul :
+			p_memdup(_stmt->pool, value, value_size);
+		arg->value_binary_size = value_size;
+	}
+}
+
+static void
+driver_cassandra_statement_bind_int64(struct sql_statement *_stmt,
+				      unsigned int column_idx, int64_t value)
+{
+	struct cassandra_sql_statement *stmt =
+		(struct cassandra_sql_statement *)_stmt;
+
+	if (stmt->cass_stmt != NULL)
+		driver_cassandra_bind_int(stmt, column_idx, value);
+	else if (stmt->prep != NULL) {
+		struct cassandra_sql_arg *arg =
+			driver_cassandra_add_pending_arg(stmt, column_idx);
+		arg->value_int64 = value;
+	}
+}
+
+static void
+driver_cassandra_statement_query(struct sql_statement *_stmt,
+				 sql_query_callback_t *callback, void *context)
+{
+	struct cassandra_sql_statement *stmt =
+		(struct cassandra_sql_statement *)_stmt;
+	struct cassandra_db *db = (struct cassandra_db *)_stmt->db;
+	const char *query = sql_statement_get_query(_stmt);
+	bool is_prepared = stmt->cass_stmt != NULL || stmt->prep != NULL;
+
+	stmt->result = driver_cassandra_query_init(db, query,
+						   CASSANDRA_QUERY_TYPE_READ,
+						   is_prepared,
+						   callback, context);
+	if (stmt->cass_stmt != NULL) {
+		stmt->result->statement = stmt->cass_stmt;
+		stmt->result->timestamp = stmt->timestamp;
+	} else if (stmt->prep != NULL) {
+		/* wait for prepare to finish */
+		return;
+	} else {
+		stmt->result->statement = cass_statement_new(query, 0);
+		stmt->result->timestamp = stmt->timestamp;
+		if (stmt->timestamp != 0) {
+			cass_statement_set_timestamp(stmt->result->statement,
+						     stmt->timestamp);
+		}
+	}
+	(void)driver_cassandra_send_query(stmt->result);
+	pool_unref(&_stmt->pool);
+}
+
+static struct sql_result *
+driver_cassandra_statement_query_s(struct sql_statement *_stmt ATTR_UNUSED)
+{
+	i_panic("cassandra: sql_statement_query_s() not supported");
+}
+
+static void
+driver_cassandra_update_stmt(struct sql_transaction_context *_ctx,
+			     struct sql_statement *_stmt,
+			     unsigned int *affected_rows)
+{
+	struct cassandra_transaction_context *ctx =
+		(struct cassandra_transaction_context *)_ctx;
+	struct cassandra_sql_statement *stmt =
+		(struct cassandra_sql_statement *)_stmt;
+
+	i_assert(affected_rows == NULL);
+
+	if (ctx->query != NULL || ctx->stmt != NULL) {
+		transaction_set_failed(ctx,
+			"Multiple changes in transaction not supported");
+		return;
+	}
+	if (stmt->prep != NULL)
+		ctx->stmt = stmt;
+	else {
+		ctx->query = i_strdup(sql_statement_get_query(_stmt));
+		ctx->query_timestamp = stmt->timestamp;
+		pool_unref(&_stmt->pool);
+	}
+}
+
+static bool driver_cassandra_have_work(struct cassandra_db *db)
+{
+	return array_not_empty(&db->pending_prepares) ||
+		array_not_empty(&db->callbacks) ||
+		array_not_empty(&db->results);
+}
+
+static void driver_cassandra_wait(struct sql_db *_db)
+{
+	struct cassandra_db *db = (struct cassandra_db *)_db;
+
+	if (!driver_cassandra_have_work(db))
+		return;
+
+	struct ioloop *prev_ioloop = current_ioloop;
+	db->ioloop = io_loop_create();
+	db->io_pipe = io_loop_move_io(&db->io_pipe);
+	while (driver_cassandra_have_work(db))
+		io_loop_run(db->ioloop);
+
+	io_loop_set_current(prev_ioloop);
+	db->io_pipe = io_loop_move_io(&db->io_pipe);
+	io_loop_set_current(db->ioloop);
+	io_loop_destroy(&db->ioloop);
+}
+
+const struct sql_db driver_cassandra_db = {
+	.name = "cassandra",
+	.flags = SQL_DB_FLAG_PREP_STATEMENTS,
+
+	.v = {
+		.init_full = driver_cassandra_init_full_v,
+		.deinit = driver_cassandra_deinit_v,
+		.connect = driver_cassandra_connect,
+		.disconnect = driver_cassandra_disconnect,
+		.escape_string = driver_cassandra_escape_string,
+		.exec = driver_cassandra_exec,
+		.query = driver_cassandra_query,
+		.query_s = driver_cassandra_query_s,
+		.wait = driver_cassandra_wait,
+
+		.transaction_begin = driver_cassandra_transaction_begin,
+		.transaction_commit = driver_cassandra_transaction_commit,
+		.transaction_commit_s = driver_cassandra_transaction_commit_s,
+		.transaction_rollback = driver_cassandra_transaction_rollback,
+
+		.update = driver_cassandra_update,
+
+		.escape_blob = driver_cassandra_escape_blob,
+
+		.prepared_statement_init = driver_cassandra_prepared_statement_init,
+		.prepared_statement_deinit = driver_cassandra_prepared_statement_deinit,
+		.statement_init = driver_cassandra_statement_init,
+		.statement_init_prepared = driver_cassandra_statement_init_prepared,
+		.statement_abort = driver_cassandra_statement_abort,
+		.statement_set_timestamp = driver_cassandra_statement_set_timestamp,
+		.statement_bind_str = driver_cassandra_statement_bind_str,
+		.statement_bind_binary = driver_cassandra_statement_bind_binary,
+		.statement_bind_int64 = driver_cassandra_statement_bind_int64,
+		.statement_query = driver_cassandra_statement_query,
+		.statement_query_s = driver_cassandra_statement_query_s,
+		.update_stmt = driver_cassandra_update_stmt,
+	}
+};
+
+const struct sql_result driver_cassandra_result = {
+	.v = {
+		driver_cassandra_result_free,
+		driver_cassandra_result_next_row,
+		driver_cassandra_result_get_fields_count,
+		driver_cassandra_result_get_field_name,
+		driver_cassandra_result_find_field,
+		driver_cassandra_result_get_field_value,
+		driver_cassandra_result_get_field_value_binary,
+		driver_cassandra_result_find_field_value,
+		driver_cassandra_result_get_values,
+		driver_cassandra_result_get_error,
+		driver_cassandra_result_more,
+	}
+};
+
+const char *driver_cassandra_version = DOVECOT_ABI_VERSION;
+
+void driver_cassandra_init(void);
+void driver_cassandra_deinit(void);
+
+void driver_cassandra_init(void)
+{
+	sql_driver_register(&driver_cassandra_db);
+}
+
+void driver_cassandra_deinit(void)
+{
+	sql_driver_unregister(&driver_cassandra_db);
+}
+
+#endif
diff --git a/src/lib-sql/driver-mysql.c b/src/lib-sql/driver-mysql.c
new file mode 100644
index 0000000..b8308cc
--- /dev/null
+++ b/src/lib-sql/driver-mysql.c
@@ -0,0 +1,835 @@
+/* Copyright (c) 2003-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "ioloop.h"
+#include "array.h"
+#include "hex-binary.h"
+#include "str.h"
+#include "net.h"
+#include "time-util.h"
+#include "sql-api-private.h"
+
+#ifdef BUILD_MYSQL
+#include <unistd.h>
+#include <time.h>
+#ifdef HAVE_ATTR_NULL
+/* ugly way to tell clang that mysql.h is a system header and we don't want
+   to enable nonnull attributes for it by default.. */
+# 4 "driver-mysql.c" 3
+#endif
+#include <mysql.h>
+#ifdef HAVE_ATTR_NULL
+# 4 "driver-mysql.c" 3
+# line 20
+#endif
+#include <errmsg.h>
+
+#define MYSQL_DEFAULT_READ_TIMEOUT_SECS 30
+#define MYSQL_DEFAULT_WRITE_TIMEOUT_SECS 30
+
+struct mysql_db {
+	struct sql_db api;
+
+	pool_t pool;
+	const char *user, *password, *dbname, *host, *unix_socket;
+	const char *ssl_cert, *ssl_key, *ssl_ca, *ssl_ca_path, *ssl_cipher;
+	int ssl_verify_server_cert;
+	const char *option_file, *option_group;
+	in_port_t port;
+	unsigned int client_flags;
+	unsigned int connect_timeout, read_timeout, write_timeout;
+	time_t last_success;
+
+	MYSQL *mysql;
+	unsigned int next_query_connection;
+
+	bool ssl_set:1;
+};
+
+struct mysql_result {
+	struct sql_result api;
+
+	MYSQL_RES *result;
+	MYSQL_ROW row;
+
+	MYSQL_FIELD *fields;
+	unsigned int fields_count;
+
+	my_ulonglong affected_rows;
+};
+
+struct mysql_transaction_context {
+	struct sql_transaction_context ctx;
+
+	pool_t query_pool;
+	const char *error;
+
+	bool failed:1;
+	bool committed:1;
+	bool commit_started:1;
+};
+
+extern const struct sql_db driver_mysql_db;
+extern const struct sql_result driver_mysql_result;
+extern const struct sql_result driver_mysql_error_result;
+
+static struct event_category event_category_mysql = {
+	.parent = &event_category_sql,
+	.name = "mysql"
+};
+
+static int driver_mysql_connect(struct sql_db *_db)
+{
+	struct mysql_db *db = (struct mysql_db *)_db;
+	const char *unix_socket, *host;
+	unsigned long client_flags = db->client_flags;
+	unsigned int secs_used;
+	time_t start_time;
+	bool failed;
+
+	i_assert(db->api.state == SQL_DB_STATE_DISCONNECTED);
+
+	sql_db_set_state(&db->api, SQL_DB_STATE_CONNECTING);
+
+	if (mysql_init(db->mysql) == NULL)
+		i_fatal("mysql_init() failed");
+
+	if (db->host == NULL) {
+		/* assume option_file overrides the host, or if not we'll just
+		   connect to localhost */
+		unix_socket = NULL;
+		host = NULL;
+	} else if (*db->host == '/') {
+		unix_socket = db->host;
+		host = NULL;
+	} else {
+		unix_socket = NULL;
+		host = db->host;
+	}
+
+	if (db->option_file != NULL) {
+		mysql_options(db->mysql, MYSQL_READ_DEFAULT_FILE,
+			      db->option_file);
+	}
+
+	if (db->host != NULL)
+		event_set_append_log_prefix(_db->event, t_strdup_printf("mysql(%s): ", db->host));
+
+	e_debug(_db->event, "Connecting");
+
+	mysql_options(db->mysql, MYSQL_OPT_CONNECT_TIMEOUT, &db->connect_timeout);
+	mysql_options(db->mysql, MYSQL_OPT_READ_TIMEOUT, &db->read_timeout);
+	mysql_options(db->mysql, MYSQL_OPT_WRITE_TIMEOUT, &db->write_timeout);
+	mysql_options(db->mysql, MYSQL_READ_DEFAULT_GROUP,
+		      db->option_group != NULL ? db->option_group : "client");
+
+	if (!db->ssl_set && (db->ssl_ca != NULL || db->ssl_ca_path != NULL)) {
+#ifdef HAVE_MYSQL_SSL
+		mysql_ssl_set(db->mysql, db->ssl_key, db->ssl_cert,
+			      db->ssl_ca, db->ssl_ca_path
+#ifdef HAVE_MYSQL_SSL_CIPHER
+			      , db->ssl_cipher
+#endif
+			     );
+#ifdef HAVE_MYSQL_SSL_VERIFY_SERVER_CERT
+		mysql_options(db->mysql, MYSQL_OPT_SSL_VERIFY_SERVER_CERT,
+			      (void *)&db->ssl_verify_server_cert);
+#endif
+		db->ssl_set = TRUE;
+#else
+		i_fatal("mysql: SSL support not compiled in "
+			"(remove ssl_ca and ssl_ca_path settings)");
+#endif
+	}
+
+#ifdef CLIENT_MULTI_RESULTS
+	client_flags |= CLIENT_MULTI_RESULTS;
+#endif
+	/* CLIENT_MULTI_RESULTS allows the use of stored procedures */
+	start_time = time(NULL);
+	failed = mysql_real_connect(db->mysql, host, db->user, db->password,
+				    db->dbname, db->port, unix_socket,
+				    client_flags) == NULL;
+	secs_used = time(NULL) - start_time;
+	if (failed) {
+		/* connecting could have taken a while. make sure that any
+		   timeouts that get added soon will get a refreshed
+		   timestamp. */
+		io_loop_time_refresh();
+
+		if (db->api.connect_delay < secs_used)
+			db->api.connect_delay = secs_used;
+		sql_db_set_state(&db->api, SQL_DB_STATE_DISCONNECTED);
+		e_error(_db->event, "Connect failed to database (%s): %s - "
+			"waiting for %u seconds before retry",
+			db->dbname, mysql_error(db->mysql), db->api.connect_delay);
+		return -1;
+	} else {
+		db->last_success = ioloop_time;
+		sql_db_set_state(&db->api, SQL_DB_STATE_IDLE);
+		return 1;
+	}
+}
+
+static void driver_mysql_disconnect(struct sql_db *_db)
+{
+	struct mysql_db *db = (struct mysql_db *)_db;
+	if (db->mysql != NULL)
+		mysql_close(db->mysql);
+	db->mysql = NULL;
+}
+
+static int driver_mysql_parse_connect_string(struct mysql_db *db,
+					     const char *connect_string,
+					     const char **error_r)
+{
+	const char *const *args, *name, *value;
+	const char **field;
+
+	db->ssl_cipher = "HIGH";
+	db->ssl_verify_server_cert = 1;
+	db->connect_timeout = SQL_CONNECT_TIMEOUT_SECS;
+	db->read_timeout = MYSQL_DEFAULT_READ_TIMEOUT_SECS;
+	db->write_timeout = MYSQL_DEFAULT_WRITE_TIMEOUT_SECS;
+
+	args = t_strsplit_spaces(connect_string, " ");
+	for (; *args != NULL; args++) {
+		value = strchr(*args, '=');
+		if (value == NULL) {
+			*error_r = t_strdup_printf("Missing value in connect string: %s",
+						   *args);
+			return -1;
+		}
+		name = t_strdup_until(*args, value);
+		value++;
+
+		field = NULL;
+		if (strcmp(name, "host") == 0 ||
+		    strcmp(name, "hostaddr") == 0)
+			field = &db->host;
+		else if (strcmp(name, "user") == 0)
+			field = &db->user;
+		else if (strcmp(name, "password") == 0)
+			field = &db->password;
+		else if (strcmp(name, "dbname") == 0)
+			field = &db->dbname;
+		else if (strcmp(name, "port") == 0) {
+			if (net_str2port(value, &db->port) < 0) {
+				*error_r = t_strdup_printf("Invalid port number: %s", value);
+				return -1;
+			}
+		} else if (strcmp(name, "client_flags") == 0) {
+			if (str_to_uint(value, &db->client_flags) < 0) {
+				*error_r = t_strdup_printf("Invalid client flags: %s", value);
+				return -1;
+			}
+		} else if (strcmp(name, "connect_timeout") == 0) {
+			if (str_to_uint(value, &db->connect_timeout) < 0) {
+				*error_r = t_strdup_printf("Invalid read_timeout: %s", value);
+				return -1;
+			}
+		} else if (strcmp(name, "read_timeout") == 0) {
+			if (str_to_uint(value, &db->read_timeout) < 0) {
+				*error_r = t_strdup_printf("Invalid read_timeout: %s", value);
+				return -1;
+			}
+		} else if (strcmp(name, "write_timeout") == 0) {
+			if (str_to_uint(value, &db->write_timeout) < 0) {
+				*error_r = t_strdup_printf("Invalid read_timeout: %s", value);
+				return -1;
+			}
+		} else if (strcmp(name, "ssl_cert") == 0)
+			field = &db->ssl_cert;
+		else if (strcmp(name, "ssl_key") == 0)
+			field = &db->ssl_key;
+		else if (strcmp(name, "ssl_ca") == 0)
+			field = &db->ssl_ca;
+		else if (strcmp(name, "ssl_ca_path") == 0)
+			field = &db->ssl_ca_path;
+		else if (strcmp(name, "ssl_cipher") == 0)
+			field = &db->ssl_cipher;
+		else if (strcmp(name, "ssl_verify_server_cert") == 0) {
+			if (strcmp(value, "yes") == 0)
+				db->ssl_verify_server_cert = 1;
+			else if (strcmp(value, "no") == 0)
+				db->ssl_verify_server_cert = 0;
+			else {
+				*error_r = t_strdup_printf("Invalid boolean: %s", value);
+				return -1;
+			}
+		} else if (strcmp(name, "option_file") == 0)
+			field = &db->option_file;
+		else if (strcmp(name, "option_group") == 0)
+			field = &db->option_group;
+		else {
+			*error_r = t_strdup_printf("Unknown connect string: %s", name);
+			return -1;
+		}
+		if (field != NULL)
+			*field = p_strdup(db->pool, value);
+	}
+
+	if (db->host == NULL && db->option_file == NULL) {
+		*error_r = "No hosts given in connect string";
+		return -1;
+	}
+	db->mysql = p_new(db->pool, MYSQL, 1);
+	return 0;
+}
+
+static int driver_mysql_init_full_v(const struct sql_settings *set,
+				    struct sql_db **db_r, const char **error_r)
+{
+	struct mysql_db *db;
+	const char *error = NULL;
+	pool_t pool;
+	int ret;
+
+	pool = pool_alloconly_create("mysql driver", 1024);
+	db = p_new(pool, struct mysql_db, 1);
+	db->pool = pool;
+	db->api = driver_mysql_db;
+	db->api.event = event_create(set->event_parent);
+	event_add_category(db->api.event, &event_category_mysql);
+	event_set_append_log_prefix(db->api.event, "mysql: ");
+	T_BEGIN {
+		ret = driver_mysql_parse_connect_string(db, set->connect_string, &error);
+		error = p_strdup(db->pool, error);
+	} T_END;
+
+	if (ret < 0) {
+		*error_r = t_strdup(error);
+		pool_unref(&db->pool);
+		return ret;
+	}
+
+	*db_r = &db->api;
+	return 0;
+}
+
+static void driver_mysql_deinit_v(struct sql_db *_db)
+{
+	struct mysql_db *db = (struct mysql_db *)_db;
+
+	_db->no_reconnect = TRUE;
+	sql_db_set_state(&db->api, SQL_DB_STATE_DISCONNECTED);
+
+	if (db->mysql != NULL)
+		mysql_close(db->mysql);
+	db->mysql = NULL;
+
+	sql_connection_log_finished(_db);
+	event_unref(&_db->event);
+	array_free(&_db->module_contexts);
+	pool_unref(&db->pool);
+}
+
+static int driver_mysql_do_query(struct mysql_db *db, const char *query,
+				 struct event *event)
+{
+	int ret, diff;
+	struct event_passthrough *e;
+
+	ret = mysql_query(db->mysql, query);
+	io_loop_time_refresh();
+	e = sql_query_finished_event(&db->api, event, query, ret == 0, &diff);
+
+	if (ret != 0) {
+		e->add_int("error_code", mysql_errno(db->mysql));
+		e->add_str("error", mysql_error(db->mysql));
+		e_debug(e->event(), SQL_QUERY_FINISHED_FMT": %s", query,
+			diff, mysql_error(db->mysql));
+	} else
+		e_debug(e->event(), SQL_QUERY_FINISHED_FMT, query, diff);
+
+	if (ret == 0)
+		return 0;
+
+	/* failed */
+	switch (mysql_errno(db->mysql)) {
+	case CR_SERVER_GONE_ERROR:
+	case CR_SERVER_LOST:
+		sql_db_set_state(&db->api, SQL_DB_STATE_DISCONNECTED);
+		break;
+	default:
+		break;
+	}
+	return -1;
+}
+
+static const char *
+driver_mysql_escape_string(struct sql_db *_db, const char *string)
+{
+	struct mysql_db *db = (struct mysql_db *)_db;
+	size_t len = strlen(string);
+	char *to;
+
+	if (_db->state == SQL_DB_STATE_DISCONNECTED) {
+		/* try connecting */
+		(void)sql_connect(&db->api);
+	}
+
+	if (db->mysql == NULL) {
+		/* FIXME: we don't have a valid connection, so fallback
+		   to using default escaping. the next query will most
+		   likely fail anyway so it shouldn't matter that much
+		   what we return here.. Anyway, this API needs
+		   changing so that the escaping function could already
+		   fail the query reliably. */
+		to = t_buffer_get(len * 2 + 1);
+		len = mysql_escape_string(to, string, len);
+		t_buffer_alloc(len + 1);
+		return to;
+	}
+
+	to = t_buffer_get(len * 2 + 1);
+	len = mysql_real_escape_string(db->mysql, to, string, len);
+	t_buffer_alloc(len + 1);
+	return to;
+}
+
+static void driver_mysql_exec(struct sql_db *_db, const char *query)
+{
+	struct mysql_db *db = (struct mysql_db *)_db;
+	struct event *event = event_create(_db->event);
+
+	(void)driver_mysql_do_query(db, query, event);
+
+	event_unref(&event);
+}
+
+static void driver_mysql_query(struct sql_db *db, const char *query,
+			       sql_query_callback_t *callback, void *context)
+{
+	struct sql_result *result;
+
+	result = sql_query_s(db, query);
+	result->callback = TRUE;
+	callback(result, context);
+	result->callback = FALSE;
+	sql_result_unref(result);
+}
+
+static struct sql_result *
+driver_mysql_query_s(struct sql_db *_db, const char *query)
+{
+	struct mysql_db *db = (struct mysql_db *)_db;
+	struct mysql_result *result;
+	struct event *event;
+	int ret;
+
+	result = i_new(struct mysql_result, 1);
+	result->api = driver_mysql_result;
+	event = event_create(_db->event);
+
+	if (driver_mysql_do_query(db, query, event) < 0)
+		result->api = driver_mysql_error_result;
+	else {
+		/* query ok */
+		result->affected_rows = mysql_affected_rows(db->mysql);
+		result->result = mysql_store_result(db->mysql);
+#ifdef CLIENT_MULTI_RESULTS
+		/* Because we've enabled CLIENT_MULTI_RESULTS, we need to read
+		   (ignore) extra results - there should not be any.
+		   ret is: -1 = done, >0 = error, 0 = more results. */
+		while ((ret = mysql_next_result(db->mysql)) == 0) ;
+#else
+		ret = -1;
+#endif
+
+		if (ret < 0 &&
+		    (result->result != NULL || mysql_errno(db->mysql) == 0)) {
+			/* ok */
+		} else {
+			/* failed */
+			if (result->result != NULL)
+				mysql_free_result(result->result);
+			result->api = driver_mysql_error_result;
+		}
+	}
+
+	result->api.db = _db;
+	result->api.refcount = 1;
+	result->api.event = event;
+	return &result->api;
+}
+
+static void driver_mysql_result_free(struct sql_result *_result)
+{
+	struct mysql_result *result = (struct mysql_result *)_result;
+
+	i_assert(_result != &sql_not_connected_result);
+	if (_result->callback)
+		return;
+
+	if (result->result != NULL)
+		mysql_free_result(result->result);
+	event_unref(&_result->event);
+	i_free(result);
+}
+
+static int driver_mysql_result_next_row(struct sql_result *_result)
+{
+	struct mysql_result *result = (struct mysql_result *)_result;
+	struct mysql_db *db = (struct mysql_db *)_result->db;
+	int ret;
+
+	if (result->result == NULL) {
+		/* no results */
+		return 0;
+	}
+
+	result->row = mysql_fetch_row(result->result);
+	if (result->row != NULL)
+		ret = 1;
+	else {
+		if (mysql_errno(db->mysql) != 0)
+			return -1;
+		ret = 0;
+	}
+	db->last_success = ioloop_time;
+	return ret;
+}
+
+static void driver_mysql_result_fetch_fields(struct mysql_result *result)
+{
+	if (result->fields != NULL)
+		return;
+
+	result->fields_count = mysql_num_fields(result->result);
+	result->fields = mysql_fetch_fields(result->result);
+}
+
+static unsigned int
+driver_mysql_result_get_fields_count(struct sql_result *_result)
+{
+	struct mysql_result *result = (struct mysql_result *)_result;
+
+        driver_mysql_result_fetch_fields(result);
+	return result->fields_count;
+}
+
+static const char *
+driver_mysql_result_get_field_name(struct sql_result *_result, unsigned int idx)
+{
+	struct mysql_result *result = (struct mysql_result *)_result;
+
+	driver_mysql_result_fetch_fields(result);
+	i_assert(idx < result->fields_count);
+	return result->fields[idx].name;
+}
+
+static int driver_mysql_result_find_field(struct sql_result *_result,
+					  const char *field_name)
+{
+	struct mysql_result *result = (struct mysql_result *)_result;
+	unsigned int i;
+
+	driver_mysql_result_fetch_fields(result);
+	for (i = 0; i < result->fields_count; i++) {
+		if (strcmp(result->fields[i].name, field_name) == 0)
+			return i;
+	}
+	return -1;
+}
+
+static const char *
+driver_mysql_result_get_field_value(struct sql_result *_result,
+				    unsigned int idx)
+{
+	struct mysql_result *result = (struct mysql_result *)_result;
+
+	return (const char *)result->row[idx];
+}
+
+static const unsigned char *
+driver_mysql_result_get_field_value_binary(struct sql_result *_result,
+					   unsigned int idx, size_t *size_r)
+{
+	struct mysql_result *result = (struct mysql_result *)_result;
+	unsigned long *lengths;
+
+	lengths = mysql_fetch_lengths(result->result);
+
+	*size_r = lengths[idx];
+	return (const void *)result->row[idx];
+}
+
+static const char *
+driver_mysql_result_find_field_value(struct sql_result *result,
+				     const char *field_name)
+{
+	int idx;
+
+	idx = driver_mysql_result_find_field(result, field_name);
+	if (idx < 0)
+		return NULL;
+	return driver_mysql_result_get_field_value(result, idx);
+}
+
+static const char *const *
+driver_mysql_result_get_values(struct sql_result *_result)
+{
+	struct mysql_result *result = (struct mysql_result *)_result;
+
+	return (const char *const *)result->row;
+}
+
+static const char *driver_mysql_result_get_error(struct sql_result *_result)
+{
+	struct mysql_db *db = (struct mysql_db *)_result->db;
+	const char *errstr;
+	unsigned int idle_time;
+	int err;
+
+	err = mysql_errno(db->mysql);
+	errstr = mysql_error(db->mysql);
+	if ((err == CR_SERVER_GONE_ERROR || err == CR_SERVER_LOST) &&
+	    db->last_success != 0) {
+		idle_time = ioloop_time - db->last_success;
+		errstr = t_strdup_printf("%s (idled for %u secs)",
+					 errstr, idle_time);
+	}
+	return errstr;
+}
+
+static struct sql_transaction_context *
+driver_mysql_transaction_begin(struct sql_db *db)
+{
+	struct mysql_transaction_context *ctx;
+
+	ctx = i_new(struct mysql_transaction_context, 1);
+	ctx->ctx.db = db;
+	ctx->query_pool = pool_alloconly_create("mysql transaction", 1024);
+	ctx->ctx.event = event_create(db->event);
+	return &ctx->ctx;
+}
+
+static void
+driver_mysql_transaction_commit(struct sql_transaction_context *ctx,
+				sql_commit_callback_t *callback, void *context)
+{
+	struct sql_commit_result result;
+	const char *error;
+
+	i_zero(&result);
+	if (sql_transaction_commit_s(&ctx, &error) < 0)
+		result.error = error;
+	callback(&result, context);
+}
+
+static int ATTR_NULL(3)
+transaction_send_query(struct mysql_transaction_context *ctx, const char *query,
+		       unsigned int *affected_rows_r)
+{
+	struct sql_result *_result;
+	int ret = 0;
+
+	if (ctx->failed)
+		return -1;
+
+	_result = sql_query_s(ctx->ctx.db, query);
+	if (sql_result_next_row(_result) < 0) {
+		ctx->error = sql_result_get_error(_result);
+		ctx->failed = TRUE;
+		ret = -1;
+	} else if (affected_rows_r != NULL) {
+		struct mysql_result *result = (struct mysql_result *)_result;
+
+		i_assert(result->affected_rows != (my_ulonglong)-1);
+		*affected_rows_r = result->affected_rows;
+	}
+	sql_result_unref(_result);
+	return ret;
+}
+
+static int driver_mysql_try_commit_s(struct mysql_transaction_context *ctx)
+{
+	struct sql_transaction_context *_ctx = &ctx->ctx;
+	bool multi = _ctx->head != NULL && _ctx->head->next != NULL;
+
+	/* wrap in BEGIN/COMMIT only if transaction has mutiple statements. */
+	if (multi && transaction_send_query(ctx, "BEGIN", NULL) < 0) {
+		if (_ctx->db->state != SQL_DB_STATE_DISCONNECTED)
+			return -1;
+		/* we got disconnected, retry */
+		return 0;
+	} else if (multi) {
+		ctx->commit_started = TRUE;
+	}
+
+	while (_ctx->head != NULL) {
+		if (transaction_send_query(ctx, _ctx->head->query,
+					   _ctx->head->affected_rows) < 0)
+			return -1;
+		_ctx->head = _ctx->head->next;
+	}
+	if (multi && transaction_send_query(ctx, "COMMIT", NULL) < 0)
+		return -1;
+	return 1;
+}
+
+static int
+driver_mysql_transaction_commit_s(struct sql_transaction_context *_ctx,
+				  const char **error_r)
+{
+	struct mysql_transaction_context *ctx =
+		(struct mysql_transaction_context *)_ctx;
+	struct mysql_db *db = (struct mysql_db *)_ctx->db;
+	int ret = 1;
+
+	*error_r = NULL;
+
+	if (_ctx->head != NULL) {
+		ret = driver_mysql_try_commit_s(ctx);
+		*error_r = t_strdup(ctx->error);
+		if (ret == 0) {
+			e_info(db->api.event, "Disconnected from database, "
+			       "retrying commit");
+			if (sql_connect(_ctx->db) >= 0) {
+				ctx->failed = FALSE;
+				ret = driver_mysql_try_commit_s(ctx);
+			}
+		}
+	}
+
+	if (ret > 0)
+		ctx->committed = TRUE;
+
+	sql_transaction_rollback(&_ctx);
+	return ret <= 0 ? -1 : 0;
+}
+
+static void
+driver_mysql_transaction_rollback(struct sql_transaction_context *_ctx)
+{
+	struct mysql_transaction_context *ctx =
+		(struct mysql_transaction_context *)_ctx;
+
+	if (ctx->failed) {
+		bool rolledback = FALSE;
+		const char *orig_error = t_strdup(ctx->error);
+		if (ctx->commit_started) {
+			/* reset failed flag so ROLLBACK is actually sent.
+			   otherwise, transaction_send_query() will return
+			   without trying to send the query. */
+			ctx->failed = FALSE;
+			if (transaction_send_query(ctx, "ROLLBACK", NULL) < 0)
+				e_debug(event_create_passthrough(_ctx->event)->
+					add_str("error", ctx->error)->event(),
+					"Rollback failed: %s", ctx->error);
+			else
+				rolledback = TRUE;
+		}
+		e_debug(sql_transaction_finished_event(_ctx)->
+			add_str("error", orig_error)->event(),
+			"Transaction failed: %s%s", orig_error,
+			rolledback ? " - Rolled back" : "");
+	} else if (ctx->committed)
+		e_debug(sql_transaction_finished_event(_ctx)->event(),
+			"Transaction committed");
+	else
+		e_debug(sql_transaction_finished_event(_ctx)->
+			add_str("error", "Rolled back")->event(),
+			 "Transaction rolled back");
+
+	event_unref(&ctx->ctx.event);
+	pool_unref(&ctx->query_pool);
+	i_free(ctx);
+}
+
+static void
+driver_mysql_update(struct sql_transaction_context *_ctx, const char *query,
+		    unsigned int *affected_rows)
+{
+	struct mysql_transaction_context *ctx =
+		(struct mysql_transaction_context *)_ctx;
+
+	sql_transaction_add_query(&ctx->ctx, ctx->query_pool,
+				  query, affected_rows);
+}
+
+static const char *
+driver_mysql_escape_blob(struct sql_db *_db ATTR_UNUSED,
+			 const unsigned char *data, size_t size)
+{
+	string_t *str = t_str_new(128);
+
+	str_append(str, "X'");
+	binary_to_hex_append(str, data, size);
+	str_append_c(str, '\'');
+	return str_c(str);
+}
+
+const struct sql_db driver_mysql_db = {
+	.name = "mysql",
+	.flags = SQL_DB_FLAG_BLOCKING | SQL_DB_FLAG_POOLED |
+		 SQL_DB_FLAG_ON_DUPLICATE_KEY,
+
+	.v = {
+		.init_full = driver_mysql_init_full_v,
+		.deinit = driver_mysql_deinit_v,
+		.connect = driver_mysql_connect,
+		.disconnect = driver_mysql_disconnect,
+		.escape_string = driver_mysql_escape_string,
+		.exec = driver_mysql_exec,
+		.query = driver_mysql_query,
+		.query_s = driver_mysql_query_s,
+
+		.transaction_begin = driver_mysql_transaction_begin,
+		.transaction_commit = driver_mysql_transaction_commit,
+		.transaction_commit_s = driver_mysql_transaction_commit_s,
+		.transaction_rollback = driver_mysql_transaction_rollback,
+
+		.update = driver_mysql_update,
+
+		.escape_blob = driver_mysql_escape_blob,
+	}
+};
+
+const struct sql_result driver_mysql_result = {
+	.v = {
+		.free = driver_mysql_result_free,
+		.next_row = driver_mysql_result_next_row,
+		.get_fields_count = driver_mysql_result_get_fields_count,
+		.get_field_name = driver_mysql_result_get_field_name,
+		.find_field = driver_mysql_result_find_field,
+		.get_field_value = driver_mysql_result_get_field_value,
+		.get_field_value_binary = driver_mysql_result_get_field_value_binary,
+		.find_field_value = driver_mysql_result_find_field_value,
+		.get_values = driver_mysql_result_get_values,
+		.get_error = driver_mysql_result_get_error,
+	}
+};
+
+static int
+driver_mysql_result_error_next_row(struct sql_result *result ATTR_UNUSED)
+{
+	return -1;
+}
+
+const struct sql_result driver_mysql_error_result = {
+	.v = {
+		.free = driver_mysql_result_free,
+		.next_row = driver_mysql_result_error_next_row,
+		.get_error = driver_mysql_result_get_error,
+	},
+	.failed_try_retry = TRUE
+};
+
+const char *driver_mysql_version = DOVECOT_ABI_VERSION;
+
+void driver_mysql_init(void);
+void driver_mysql_deinit(void);
+
+void driver_mysql_init(void)
+{
+	sql_driver_register(&driver_mysql_db);
+}
+
+void driver_mysql_deinit(void)
+{
+	sql_driver_unregister(&driver_mysql_db);
+}
+
+#endif
diff --git a/src/lib-sql/driver-pgsql.c b/src/lib-sql/driver-pgsql.c
new file mode 100644
index 0000000..e4b0c63
--- /dev/null
+++ b/src/lib-sql/driver-pgsql.c
@@ -0,0 +1,1344 @@
+/* Copyright (c) 2004-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "array.h"
+#include "ioloop.h"
+#include "hex-binary.h"
+#include "str.h"
+#include "time-util.h"
+#include "sql-api-private.h"
+#include "llist.h"
+
+#ifdef BUILD_PGSQL
+#include <libpq-fe.h>
+
+#define PGSQL_DNS_WARN_MSECS 500
+
+struct pgsql_db {
+	struct sql_db api;
+
+	pool_t pool;
+	char *connect_string;
+	char *host;
+	PGconn *pg;
+
+	struct io *io;
+	struct timeout *to_connect;
+	enum io_condition io_dir;
+
+	struct pgsql_result *pending_results;
+	struct pgsql_result *cur_result;
+	struct ioloop *ioloop, *orig_ioloop;
+	struct sql_result *sync_result;
+
+	bool (*next_callback)(void *);
+	void *next_context;
+
+	char *error;
+	const char *connect_state;
+
+	bool fatal_error:1;
+};
+
+struct pgsql_binary_value {
+	unsigned char *value;
+	size_t size;
+};
+
+struct pgsql_result {
+	struct sql_result api;
+
+	struct pgsql_result *prev, *next;
+
+	PGresult *pgres;
+	struct timeout *to;
+
+	unsigned int rownum, rows;
+	unsigned int fields_count;
+	const char **fields;
+	const char **values;
+	char *query;
+
+	ARRAY(struct pgsql_binary_value) binary_values;
+
+	sql_query_callback_t *callback;
+	void *context;
+
+	bool timeout:1;
+};
+
+struct pgsql_transaction_context {
+	struct sql_transaction_context ctx;
+	int refcount;
+
+	sql_commit_callback_t *callback;
+	void *context;
+
+	pool_t query_pool;
+	const char *error;
+
+	bool failed:1;
+};
+
+extern const struct sql_db driver_pgsql_db;
+extern const struct sql_result driver_pgsql_result;
+
+static void result_finish(struct pgsql_result *result);
+static void
+transaction_update_callback(struct sql_result *result,
+			    struct sql_transaction_query *query);
+
+static struct event_category event_category_pgsql = {
+	.parent = &event_category_sql,
+	.name = "pgsql"
+};
+
+static void driver_pgsql_set_state(struct pgsql_db *db, enum sql_db_state state)
+{
+	i_assert(state == SQL_DB_STATE_BUSY || db->cur_result == NULL);
+
+	/* switch back to original ioloop in case the caller wants to
+	   add/remove timeouts */
+	if (db->ioloop != NULL)
+		io_loop_set_current(db->orig_ioloop);
+	sql_db_set_state(&db->api, state);
+	if (db->ioloop != NULL)
+		io_loop_set_current(db->ioloop);
+}
+
+static bool driver_pgsql_next_callback(struct pgsql_db *db)
+{
+	bool (*next_callback)(void *) = db->next_callback;
+	void *next_context = db->next_context;
+
+	if (next_callback == NULL)
+		return FALSE;
+
+	db->next_callback = NULL;
+	db->next_context = NULL;
+	return next_callback(next_context);
+}
+
+static void driver_pgsql_stop_io(struct pgsql_db *db)
+{
+	if (db->io != NULL) {
+		io_remove(&db->io);
+		db->io_dir = 0;
+	}
+}
+
+static void driver_pgsql_close(struct pgsql_db *db)
+{
+	db->io_dir = 0;
+	db->fatal_error = FALSE;
+
+	driver_pgsql_stop_io(db);
+
+	PQfinish(db->pg);
+	db->pg = NULL;
+
+	timeout_remove(&db->to_connect);
+
+	driver_pgsql_set_state(db, SQL_DB_STATE_DISCONNECTED);
+
+	if (db->ioloop != NULL) {
+		/* running a sync query, stop it */
+		io_loop_stop(db->ioloop);
+	}
+	driver_pgsql_next_callback(db);
+}
+
+static const char *last_error(struct pgsql_db *db)
+{
+	const char *msg;
+	size_t len;
+
+	msg = PQerrorMessage(db->pg);
+	if (msg == NULL)
+		return "(no error set)";
+
+	/* Error message should contain trailing \n, we don't want it */
+	len = strlen(msg);
+	return len == 0 || msg[len-1] != '\n' ? msg :
+		t_strndup(msg, len-1);
+}
+
+static void connect_callback(struct pgsql_db *db)
+{
+	enum io_condition io_dir = 0;
+	int ret;
+
+	driver_pgsql_stop_io(db);
+
+	while ((ret = PQconnectPoll(db->pg)) == PGRES_POLLING_ACTIVE)
+		;
+
+	switch (ret) {
+	case PGRES_POLLING_READING:
+		db->connect_state = "wait for input";
+		io_dir = IO_READ;
+		break;
+	case PGRES_POLLING_WRITING:
+		db->connect_state = "wait for output";
+		io_dir = IO_WRITE;
+		break;
+	case PGRES_POLLING_OK:
+		break;
+	case PGRES_POLLING_FAILED:
+		e_error(db->api.event, "Connect failed to database %s: %s (state: %s)",
+			PQdb(db->pg), last_error(db), db->connect_state);
+		driver_pgsql_close(db);
+		return;
+	}
+
+	if (io_dir != 0) {
+		db->io = io_add(PQsocket(db->pg), io_dir, connect_callback, db);
+		db->io_dir = io_dir;
+	}
+
+	if (io_dir == 0) {
+		db->connect_state = "connected";
+		timeout_remove(&db->to_connect);
+		if (PQserverVersion(db->pg) >= 90500) {
+			/* v9.5+ */
+			db->api.flags |= SQL_DB_FLAG_ON_CONFLICT_DO;
+		}
+		driver_pgsql_set_state(db, SQL_DB_STATE_IDLE);
+		if (db->ioloop != NULL) {
+			/* driver_pgsql_sync_init() waiting for connection to
+			   finish */
+			io_loop_stop(db->ioloop);
+		}
+	}
+}
+
+static void driver_pgsql_connect_timeout(struct pgsql_db *db)
+{
+	unsigned int secs = ioloop_time - db->api.last_connect_try;
+
+	e_error(db->api.event, "Connect failed: Timeout after %u seconds (state: %s)",
+		secs, db->connect_state);
+	driver_pgsql_close(db);
+}
+
+static int driver_pgsql_connect(struct sql_db *_db)
+{
+	struct pgsql_db *db = (struct pgsql_db *)_db;
+	struct timeval tv_start;
+	int msecs;
+
+	i_assert(db->api.state == SQL_DB_STATE_DISCONNECTED);
+
+	io_loop_time_refresh();
+	tv_start = ioloop_timeval;
+
+	db->pg = PQconnectStart(db->connect_string);
+	if (db->pg == NULL) {
+		i_fatal("pgsql: PQconnectStart() failed (out of memory)");
+	}
+
+	if (PQstatus(db->pg) == CONNECTION_BAD) {
+		e_error(_db->event, "Connect failed to database %s: %s",
+			PQdb(db->pg), last_error(db));
+		driver_pgsql_close(db);
+		return -1;
+	}
+	/* PQconnectStart() blocks on host name resolving. Log a warning if
+	   it takes too long. Also don't include time spent on that in the
+	   connect timeout (by refreshing ioloop time). */
+	io_loop_time_refresh();
+	msecs = timeval_diff_msecs(&ioloop_timeval, &tv_start);
+	if (msecs > PGSQL_DNS_WARN_MSECS) {
+		e_warning(_db->event, "DNS lookup took %d.%03d s",
+			  msecs/1000, msecs % 1000);
+	}
+
+	/* nonblocking connecting begins. */
+	if (PQsetnonblocking(db->pg, 1) < 0)
+		e_error(_db->event, "PQsetnonblocking() failed");
+	i_assert(db->to_connect == NULL);
+	db->to_connect = timeout_add(SQL_CONNECT_TIMEOUT_SECS * 1000,
+				     driver_pgsql_connect_timeout, db);
+	db->connect_state = "connecting";
+	db->io = io_add(PQsocket(db->pg), IO_WRITE, connect_callback, db);
+	db->io_dir = IO_WRITE;
+	driver_pgsql_set_state(db, SQL_DB_STATE_CONNECTING);
+	return 0;
+}
+
+static void driver_pgsql_disconnect(struct sql_db *_db)
+{
+	struct pgsql_db *db = (struct pgsql_db *)_db;
+
+	if (db->cur_result != NULL && db->cur_result->to != NULL) {
+		driver_pgsql_stop_io(db);
+		result_finish(db->cur_result);
+	}
+
+	_db->no_reconnect = TRUE;
+	driver_pgsql_close(db);
+	_db->no_reconnect = FALSE;
+}
+
+static void driver_pgsql_free(struct pgsql_db **_db)
+{
+	struct pgsql_db *db = *_db;
+	*_db = NULL;
+
+	event_unref(&db->api.event);
+	i_free(db->connect_string);
+	i_free(db->host);
+	i_free(db->error);
+	array_free(&db->api.module_contexts);
+	i_free(db);
+}
+
+static enum sql_db_flags driver_pgsql_get_flags(struct sql_db *db)
+{
+	switch (db->state) {
+	case SQL_DB_STATE_DISCONNECTED:
+		if (sql_connect(db) < 0)
+			break;
+		/* fall through */
+	case SQL_DB_STATE_CONNECTING:
+		/* Wait for connection to finish, so we can get the flags
+		   reliably. */
+		sql_wait(db);
+		break;
+	case SQL_DB_STATE_IDLE:
+	case SQL_DB_STATE_BUSY:
+		break;
+	}
+	return db->flags;
+}
+
+static int driver_pgsql_init_full_v(const struct sql_settings *set,
+				    struct sql_db **db_r, const char **error_r ATTR_UNUSED)
+{
+	struct pgsql_db *db;
+
+	db = i_new(struct pgsql_db, 1);
+	db->connect_string = i_strdup(set->connect_string);
+	db->api = driver_pgsql_db;
+	db->api.event = event_create(set->event_parent);
+	event_add_category(db->api.event, &event_category_pgsql);
+
+	/* NOTE: Connection string will be parsed by pgsql itself
+		 We only pick the host part here */
+	T_BEGIN {
+		const char *const *arg = t_strsplit(db->connect_string, " ");
+
+		for (; *arg != NULL; arg++) {
+			if (str_begins(*arg, "host="))
+				db->host = i_strdup(*arg + 5);
+
+		}
+	} T_END;
+
+	event_set_append_log_prefix(db->api.event, t_strdup_printf("pgsql(%s): ", db->host));
+
+	*db_r = &db->api;
+	return 0;
+}
+
+static void driver_pgsql_deinit_v(struct sql_db *_db)
+{
+	struct pgsql_db *db = (struct pgsql_db *)_db;
+
+	driver_pgsql_disconnect(_db);
+	driver_pgsql_free(&db);
+}
+
+static void driver_pgsql_set_idle(struct pgsql_db *db)
+{
+	i_assert(db->api.state == SQL_DB_STATE_BUSY);
+
+	if (db->fatal_error)
+		driver_pgsql_close(db);
+	else if (!driver_pgsql_next_callback(db))
+		driver_pgsql_set_state(db, SQL_DB_STATE_IDLE);
+}
+
+static void consume_results(struct pgsql_db *db)
+{
+	PGresult *pgres;
+
+	driver_pgsql_stop_io(db);
+
+	while (PQconsumeInput(db->pg) != 0) {
+		if (PQisBusy(db->pg) != 0) {
+			db->io = io_add(PQsocket(db->pg), IO_READ,
+					consume_results, db);
+			db->io_dir = IO_READ;
+			return;
+		}
+
+		pgres = PQgetResult(db->pg);
+		if (pgres == NULL)
+			break;
+		PQclear(pgres);
+	}
+
+	if (PQstatus(db->pg) == CONNECTION_BAD)
+		driver_pgsql_close(db);
+	else
+		driver_pgsql_set_idle(db);
+}
+
+static void driver_pgsql_result_free(struct sql_result *_result)
+{
+	struct pgsql_db *db = (struct pgsql_db *)_result->db;
+        struct pgsql_result *result = (struct pgsql_result *)_result;
+	bool success;
+
+	i_assert(!result->api.callback);
+	i_assert(db->cur_result == result);
+	i_assert(result->callback == NULL);
+
+	if (_result == db->sync_result)
+		db->sync_result = NULL;
+	db->cur_result = NULL;
+
+	success = result->pgres != NULL && !db->fatal_error;
+	if (result->pgres != NULL) {
+		PQclear(result->pgres);
+		result->pgres = NULL;
+	}
+
+	if (success) {
+		/* we'll have to read the rest of the results as well */
+		i_assert(db->io == NULL);
+		consume_results(db);
+	} else {
+		driver_pgsql_set_idle(db);
+	}
+
+	if (array_is_created(&result->binary_values)) {
+		struct pgsql_binary_value *value;
+
+		array_foreach_modifiable(&result->binary_values, value)
+			PQfreemem(value->value);
+		array_free(&result->binary_values);
+	}
+
+	event_unref(&result->api.event);
+	i_free(result->query);
+	i_free(result->fields);
+	i_free(result->values);
+	i_free(result);
+}
+
+static void result_finish(struct pgsql_result *result)
+{
+	struct pgsql_db *db = (struct pgsql_db *)result->api.db;
+	bool free_result = TRUE;
+	int duration;
+
+	i_assert(db->io == NULL);
+	timeout_remove(&result->to);
+	DLLIST_REMOVE(&db->pending_results, result);
+
+	/* if connection to server was lost, we don't yet see that the
+	   connection is bad. we only see the fatal error, so assume it also
+	   means disconnection. */
+	if (PQstatus(db->pg) == CONNECTION_BAD || result->pgres == NULL ||
+	    PQresultStatus(result->pgres) == PGRES_FATAL_ERROR)
+		db->fatal_error = TRUE;
+
+	if (db->fatal_error) {
+		result->api.failed = TRUE;
+		result->api.failed_try_retry = TRUE;
+	}
+
+	/* emit event */
+	if (result->api.failed) {
+		const char *error = result->timeout ? "Timed out" : last_error(db);
+		struct event_passthrough *e =
+			sql_query_finished_event(&db->api, result->api.event,
+						 result->query, TRUE, &duration);
+		e->add_str("error", error);
+		e_debug(e->event(), SQL_QUERY_FINISHED_FMT": %s", result->query,
+			duration, error);
+	} else {
+		e_debug(sql_query_finished_event(&db->api, result->api.event,
+						 result->query, FALSE, &duration)->
+						 event(),
+			SQL_QUERY_FINISHED_FMT, result->query, duration);
+	}
+	result->api.callback = TRUE;
+	T_BEGIN {
+		if (result->callback != NULL)
+			result->callback(&result->api, result->context);
+	} T_END;
+	result->api.callback = FALSE;
+
+	free_result = db->sync_result != &result->api;
+	if (db->ioloop != NULL)
+		io_loop_stop(db->ioloop);
+
+	i_assert(!free_result || result->api.refcount > 0);
+	result->callback = NULL;
+	if (free_result)
+		sql_result_unref(&result->api);
+}
+
+static void get_result(struct pgsql_result *result)
+{
+        struct pgsql_db *db = (struct pgsql_db *)result->api.db;
+
+	driver_pgsql_stop_io(db);
+
+	if (PQconsumeInput(db->pg) == 0) {
+		result_finish(result);
+		return;
+	}
+
+	if (PQisBusy(db->pg) != 0) {
+		db->io = io_add(PQsocket(db->pg), IO_READ,
+				get_result, result);
+		db->io_dir = IO_READ;
+		return;
+	}
+
+	result->pgres = PQgetResult(db->pg);
+	result_finish(result);
+}
+
+static void flush_callback(struct pgsql_result *result)
+{
+        struct pgsql_db *db = (struct pgsql_db *)result->api.db;
+	int ret;
+
+	driver_pgsql_stop_io(db);
+
+	ret = PQflush(db->pg);
+	if (ret > 0) {
+		db->io = io_add(PQsocket(db->pg), IO_WRITE,
+				flush_callback, result);
+		db->io_dir = IO_WRITE;
+		return;
+	}
+
+	if (ret < 0) {
+		result_finish(result);
+	} else {
+		/* all flushed */
+		get_result(result);
+	}
+}
+
+static void query_timeout(struct pgsql_result *result)
+{
+        struct pgsql_db *db = (struct pgsql_db *)result->api.db;
+
+	driver_pgsql_stop_io(db);
+
+	result->timeout = TRUE;
+	result_finish(result);
+}
+
+static void do_query(struct pgsql_result *result, const char *query)
+{
+        struct pgsql_db *db = (struct pgsql_db *)result->api.db;
+	int ret;
+
+	i_assert(SQL_DB_IS_READY(&db->api));
+	i_assert(db->cur_result == NULL);
+	i_assert(db->io == NULL);
+
+	driver_pgsql_set_state(db, SQL_DB_STATE_BUSY);
+	db->cur_result = result;
+	DLLIST_PREPEND(&db->pending_results, result);
+	result->to = timeout_add(SQL_QUERY_TIMEOUT_SECS * 1000,
+				 query_timeout, result);
+	result->query = i_strdup(query);
+
+	if (PQsendQuery(db->pg, query) == 0 ||
+	    (ret = PQflush(db->pg)) < 0) {
+		/* failed to send query */
+		result_finish(result);
+		return;
+	}
+
+	if (ret > 0) {
+		/* write blocks */
+		db->io = io_add(PQsocket(db->pg), IO_WRITE,
+				flush_callback, result);
+		db->io_dir = IO_WRITE;
+	} else {
+		get_result(result);
+	}
+}
+
+static const char *
+driver_pgsql_escape_string(struct sql_db *_db, const char *string)
+{
+	struct pgsql_db *db = (struct pgsql_db *)_db;
+	size_t len = strlen(string);
+	char *to;
+
+#ifdef HAVE_PQESCAPE_STRING_CONN
+	if (db->api.state == SQL_DB_STATE_DISCONNECTED) {
+		/* try connecting again */
+		(void)sql_connect(&db->api);
+	}
+	if (db->api.state != SQL_DB_STATE_DISCONNECTED) {
+		int error;
+
+		to = t_buffer_get(len * 2 + 1);
+		len = PQescapeStringConn(db->pg, to, string, len, &error);
+	} else
+#endif
+	{
+		to = t_buffer_get(len * 2 + 1);
+		len = PQescapeString(to, string, len);
+	}
+	t_buffer_alloc(len + 1);
+	return to;
+}
+
+static void exec_callback(struct sql_result *_result,
+			  void *context ATTR_UNUSED)
+{
+	struct pgsql_result *result = (struct pgsql_result*)_result;
+	result_finish(result);
+}
+
+static void driver_pgsql_exec(struct sql_db *db, const char *query)
+{
+	struct pgsql_result *result;
+
+	result = i_new(struct pgsql_result, 1);
+	result->api = driver_pgsql_result;
+	result->api.db = db;
+	result->api.refcount = 1;
+	result->api.event = event_create(db->event);
+	result->callback = exec_callback;
+	do_query(result, query);
+}
+
+static void driver_pgsql_query(struct sql_db *db, const char *query,
+			       sql_query_callback_t *callback, void *context)
+{
+	struct pgsql_result *result;
+
+	result = i_new(struct pgsql_result, 1);
+	result->api = driver_pgsql_result;
+	result->api.db = db;
+	result->api.refcount = 1;
+	result->api.event = event_create(db->event);
+	result->callback = callback;
+	result->context = context;
+	do_query(result, query);
+}
+
+static void pgsql_query_s_callback(struct sql_result *result, void *context)
+{
+        struct pgsql_db *db = context;
+
+	db->sync_result = result;
+}
+
+static void driver_pgsql_sync_init(struct pgsql_db *db)
+{
+	bool add_to_connect;
+
+	db->orig_ioloop = current_ioloop;
+	if (db->io == NULL) {
+		db->ioloop = io_loop_create();
+		return;
+	}
+
+	i_assert(db->api.state == SQL_DB_STATE_CONNECTING);
+
+	/* have to move our existing I/O and timeout handlers to new I/O loop */
+	io_remove(&db->io);
+
+	add_to_connect = (db->to_connect != NULL);
+	timeout_remove(&db->to_connect);
+
+	db->ioloop = io_loop_create();
+	if (add_to_connect) {
+		db->to_connect = timeout_add(SQL_CONNECT_TIMEOUT_SECS * 1000,
+					     driver_pgsql_connect_timeout, db);
+	}
+	db->io = io_add(PQsocket(db->pg), db->io_dir, connect_callback, db);
+	/* wait for connecting to finish */
+	io_loop_run(db->ioloop);
+}
+
+static void driver_pgsql_sync_deinit(struct pgsql_db *db)
+{
+	io_loop_destroy(&db->ioloop);
+}
+
+static struct sql_result *
+driver_pgsql_sync_query(struct pgsql_db *db, const char *query)
+{
+	struct sql_result *result;
+
+	i_assert(db->sync_result == NULL);
+
+	switch (db->api.state) {
+	case SQL_DB_STATE_CONNECTING:
+	case SQL_DB_STATE_BUSY:
+		i_unreached();
+	case SQL_DB_STATE_DISCONNECTED:
+		sql_not_connected_result.refcount++;
+		return &sql_not_connected_result;
+	case SQL_DB_STATE_IDLE:
+		break;
+	}
+
+	driver_pgsql_query(&db->api, query, pgsql_query_s_callback, db);
+	if (db->sync_result == NULL)
+		io_loop_run(db->ioloop);
+
+	i_assert(db->io == NULL);
+
+	result = db->sync_result;
+	if (result == &sql_not_connected_result) {
+		/* we don't end up in pgsql's free function, so sync_result
+		   won't be set to NULL if we don't do it here. */
+		db->sync_result = NULL;
+	} else if (result == NULL) {
+		result = &sql_not_connected_result;
+		result->refcount++;
+	}
+
+	i_assert(db->io == NULL);
+	return result;
+}
+
+static struct sql_result *
+driver_pgsql_query_s(struct sql_db *_db, const char *query)
+{
+	struct pgsql_db *db = (struct pgsql_db *)_db;
+	struct sql_result *result;
+
+	driver_pgsql_sync_init(db);
+	result = driver_pgsql_sync_query(db, query);
+	driver_pgsql_sync_deinit(db);
+	return result;
+}
+
+static int driver_pgsql_result_next_row(struct sql_result *_result)
+{
+	struct pgsql_result *result = (struct pgsql_result *)_result;
+	struct pgsql_db *db = (struct pgsql_db *)_result->db;
+
+	if (result->rows != 0) {
+		/* second time we're here */
+		if (++result->rownum < result->rows)
+			return 1;
+
+		/* end of this packet. see if there's more. FIXME: this may
+		   block, but the current API doesn't provide a non-blocking
+		   way to do this.. */
+		PQclear(result->pgres);
+		result->pgres = PQgetResult(db->pg);
+		if (result->pgres == NULL)
+			return 0;
+	}
+
+	if (result->pgres == NULL) {
+		_result->failed = TRUE;
+		return -1;
+	}
+
+	switch (PQresultStatus(result->pgres)) {
+	case PGRES_COMMAND_OK:
+		/* no rows returned */
+		return 0;
+	case PGRES_TUPLES_OK:
+		result->rows = PQntuples(result->pgres);
+		return result->rows > 0 ? 1 : 0;
+	case PGRES_EMPTY_QUERY:
+	case PGRES_NONFATAL_ERROR:
+		/* nonfatal error */
+		_result->failed = TRUE;
+		return -1;
+	default:
+		/* treat as fatal error */
+		_result->failed = TRUE;
+		db->fatal_error = TRUE;
+		return -1;
+	}
+}
+
+static void driver_pgsql_result_fetch_fields(struct pgsql_result *result)
+{
+	unsigned int i;
+
+	if (result->fields != NULL)
+		return;
+
+	/* @UNSAFE */
+	result->fields_count = PQnfields(result->pgres);
+	result->fields = i_new(const char *, result->fields_count);
+	for (i = 0; i < result->fields_count; i++)
+		result->fields[i] = PQfname(result->pgres, i);
+}
+
+static unsigned int
+driver_pgsql_result_get_fields_count(struct sql_result *_result)
+{
+	struct pgsql_result *result = (struct pgsql_result *)_result;
+
+        driver_pgsql_result_fetch_fields(result);
+	return result->fields_count;
+}
+
+static const char *
+driver_pgsql_result_get_field_name(struct sql_result *_result, unsigned int idx)
+{
+	struct pgsql_result *result = (struct pgsql_result *)_result;
+
+	driver_pgsql_result_fetch_fields(result);
+	i_assert(idx < result->fields_count);
+	return result->fields[idx];
+}
+
+static int driver_pgsql_result_find_field(struct sql_result *_result,
+					  const char *field_name)
+{
+	struct pgsql_result *result = (struct pgsql_result *)_result;
+	unsigned int i;
+
+	driver_pgsql_result_fetch_fields(result);
+	for (i = 0; i < result->fields_count; i++) {
+		if (strcmp(result->fields[i], field_name) == 0)
+			return i;
+	}
+	return -1;
+}
+
+static const char *
+driver_pgsql_result_get_field_value(struct sql_result *_result,
+				    unsigned int idx)
+{
+	struct pgsql_result *result = (struct pgsql_result *)_result;
+
+	if (PQgetisnull(result->pgres, result->rownum, idx) != 0)
+		return NULL;
+
+	return PQgetvalue(result->pgres, result->rownum, idx);
+}
+
+static const unsigned char *
+driver_pgsql_result_get_field_value_binary(struct sql_result *_result,
+					   unsigned int idx, size_t *size_r)
+{
+	struct pgsql_result *result = (struct pgsql_result *)_result;
+	const char *value;
+	struct pgsql_binary_value *binary_value;
+
+	if (PQgetisnull(result->pgres, result->rownum, idx) != 0) {
+		*size_r = 0;
+		return NULL;
+	}
+
+	value = PQgetvalue(result->pgres, result->rownum, idx);
+
+	if (!array_is_created(&result->binary_values))
+		i_array_init(&result->binary_values, idx + 1);
+
+	binary_value = array_idx_get_space(&result->binary_values, idx);
+	if (binary_value->value == NULL) {
+		binary_value->value =
+			PQunescapeBytea((const unsigned char *)value,
+					&binary_value->size);
+	}
+
+	*size_r = binary_value->size;
+	return binary_value->value;
+}
+
+static const char *
+driver_pgsql_result_find_field_value(struct sql_result *result,
+				     const char *field_name)
+{
+	int idx;
+
+	idx = driver_pgsql_result_find_field(result, field_name);
+	if (idx < 0)
+		return NULL;
+	return driver_pgsql_result_get_field_value(result, idx);
+}
+
+static const char *const *
+driver_pgsql_result_get_values(struct sql_result *_result)
+{
+	struct pgsql_result *result = (struct pgsql_result *)_result;
+	unsigned int i;
+
+	if (result->values == NULL) {
+		driver_pgsql_result_fetch_fields(result);
+		result->values = i_new(const char *, result->fields_count);
+	}
+
+	/* @UNSAFE */
+	for (i = 0; i < result->fields_count; i++) {
+		result->values[i] =
+                        driver_pgsql_result_get_field_value(_result, i);
+	}
+
+	return result->values;
+}
+
+static const char *driver_pgsql_result_get_error(struct sql_result *_result)
+{
+	struct pgsql_result *result = (struct pgsql_result *)_result;
+	struct pgsql_db *db = (struct pgsql_db *)_result->db;
+	const char *msg;
+	size_t len;
+
+	i_free_and_null(db->error);
+
+	if (result->timeout) {
+		db->error = i_strdup("Query timed out");
+	} else if (result->pgres == NULL) {
+		/* connection error */
+		db->error = i_strdup(last_error(db));
+	} else {
+		msg = PQresultErrorMessage(result->pgres);
+		if (msg == NULL)
+			return "(no error set)";
+
+		/* Error message should contain trailing \n, we don't want it */
+		len = strlen(msg);
+		db->error = len == 0 || msg[len-1] != '\n' ?
+			i_strdup(msg) : i_strndup(msg, len-1);
+	}
+	return db->error;
+}
+
+static struct sql_transaction_context *
+driver_pgsql_transaction_begin(struct sql_db *db)
+{
+	struct pgsql_transaction_context *ctx;
+
+	ctx = i_new(struct pgsql_transaction_context, 1);
+	ctx->ctx.db = db;
+	ctx->ctx.event = event_create(db->event);
+	/* we need to be able to handle multiple open transactions, so at least
+	   for now just keep them in memory until commit time. */
+	ctx->query_pool = pool_alloconly_create("pgsql transaction", 1024);
+	return &ctx->ctx;
+}
+
+static void
+driver_pgsql_transaction_free(struct pgsql_transaction_context *ctx)
+{
+	pool_unref(&ctx->query_pool);
+	event_unref(&ctx->ctx.event);
+	i_free(ctx);
+}
+
+static void
+transaction_commit_callback(struct sql_result *result,
+			    struct pgsql_transaction_context *ctx)
+{
+	struct sql_commit_result commit_result;
+
+	i_zero(&commit_result);
+	if (sql_result_next_row(result) < 0) {
+		commit_result.error = sql_result_get_error(result);
+		commit_result.error_type = sql_result_get_error_type(result);
+	}
+	ctx->callback(&commit_result, ctx->context);
+	driver_pgsql_transaction_free(ctx);
+}
+
+static bool transaction_send_next(void *context)
+{
+	struct pgsql_transaction_context *ctx = context;
+
+	i_assert(!ctx->failed);
+
+	if (ctx->ctx.db->state == SQL_DB_STATE_BUSY) {
+		/* kludgy.. */
+		ctx->ctx.db->state = SQL_DB_STATE_IDLE;
+	} else if (!SQL_DB_IS_READY(ctx->ctx.db)) {
+		struct sql_commit_result commit_result = {
+			.error = "Not connected"
+		};
+		ctx->callback(&commit_result, ctx->context);
+		return FALSE;
+	}
+
+	if (ctx->ctx.head != NULL) {
+		struct sql_transaction_query *query = ctx->ctx.head;
+
+		ctx->ctx.head = ctx->ctx.head->next;
+		sql_query(ctx->ctx.db, query->query,
+			  transaction_update_callback, query);
+	} else {
+		sql_query(ctx->ctx.db, "COMMIT",
+			  transaction_commit_callback, ctx);
+	}
+	return TRUE;
+}
+
+static void
+transaction_commit_error_callback(struct pgsql_transaction_context *ctx,
+				  struct sql_result *result)
+{
+	struct sql_commit_result commit_result;
+
+	i_zero(&commit_result);
+	commit_result.error = sql_result_get_error(result);
+	commit_result.error_type = sql_result_get_error_type(result);
+	e_debug(sql_transaction_finished_event(&ctx->ctx)->
+		add_str("error", commit_result.error)->event(),
+		"Transaction failed: %s", commit_result.error);
+	ctx->callback(&commit_result, ctx->context);
+}
+
+static void
+transaction_begin_callback(struct sql_result *result,
+			   struct pgsql_transaction_context *ctx)
+{
+	struct pgsql_db *db = (struct pgsql_db *)result->db;
+
+	i_assert(result->db == ctx->ctx.db);
+
+	if (sql_result_next_row(result) < 0) {
+		transaction_commit_error_callback(ctx, result);
+		driver_pgsql_transaction_free(ctx);
+		return;
+	}
+	i_assert(db->next_callback == NULL);
+	db->next_callback = transaction_send_next;
+	db->next_context = ctx;
+}
+
+static void
+transaction_update_callback(struct sql_result *result,
+			    struct sql_transaction_query *query)
+{
+	struct pgsql_transaction_context *ctx =
+		(struct pgsql_transaction_context *)query->trans;
+	struct pgsql_db *db = (struct pgsql_db *)result->db;
+
+	if (sql_result_next_row(result) < 0) {
+		transaction_commit_error_callback(ctx, result);
+		driver_pgsql_transaction_free(ctx);
+		return;
+	}
+
+	if (query->affected_rows != NULL) {
+		struct pgsql_result *pg_result = (struct pgsql_result *)result;
+
+		if (str_to_uint(PQcmdTuples(pg_result->pgres),
+				query->affected_rows) < 0)
+			i_unreached();
+	}
+	i_assert(db->next_callback == NULL);
+	db->next_callback = transaction_send_next;
+	db->next_context = ctx;
+}
+
+static void
+transaction_trans_query_callback(struct sql_result *result,
+				 struct sql_transaction_query *query)
+{
+	struct pgsql_transaction_context *ctx =
+		(struct pgsql_transaction_context *)query->trans;
+	struct sql_commit_result commit_result;
+
+	if (sql_result_next_row(result) < 0) {
+		transaction_commit_error_callback(ctx, result);
+		driver_pgsql_transaction_free(ctx);
+		return;
+	}
+
+	if (query->affected_rows != NULL) {
+		struct pgsql_result *pg_result = (struct pgsql_result *)result;
+
+		if (str_to_uint(PQcmdTuples(pg_result->pgres),
+				query->affected_rows) < 0)
+			i_unreached();
+	}
+	e_debug(sql_transaction_finished_event(&ctx->ctx)->event(),
+		"Transaction committed");
+	i_zero(&commit_result);
+	ctx->callback(&commit_result, ctx->context);
+	driver_pgsql_transaction_free(ctx);
+}
+
+static void
+driver_pgsql_transaction_commit(struct sql_transaction_context *_ctx,
+				sql_commit_callback_t *callback, void *context)
+{
+	struct pgsql_transaction_context *ctx =
+		(struct pgsql_transaction_context *)_ctx;
+	struct sql_commit_result result;
+
+	i_zero(&result);
+	ctx->callback = callback;
+	ctx->context = context;
+
+	if (ctx->failed || _ctx->head == NULL) {
+		if (ctx->failed) {
+			result.error = ctx->error;
+			e_debug(sql_transaction_finished_event(_ctx)->
+				add_str("error", ctx->error)->event(),
+				"Transaction failed: %s", ctx->error);
+		} else {
+			e_debug(sql_transaction_finished_event(_ctx)->event(),
+				"Transaction committed");
+		}
+		callback(&result, context);
+		driver_pgsql_transaction_free(ctx);
+	} else if (_ctx->head->next == NULL) {
+		/* just a single query, send it */
+		sql_query(_ctx->db, _ctx->head->query,
+			  transaction_trans_query_callback, _ctx->head);
+	} else {
+		/* multiple queries, use a transaction */
+		i_assert(_ctx->db->v.query == driver_pgsql_query);
+		sql_query(_ctx->db, "BEGIN", transaction_begin_callback, ctx);
+	}
+}
+
+static void
+commit_multi_fail(struct pgsql_transaction_context *ctx,
+		  struct sql_result *result, const char *query)
+{
+	ctx->failed = TRUE;
+	ctx->error = t_strdup_printf("%s (query: %s)",
+				     sql_result_get_error(result), query);
+	sql_result_unref(result);
+}
+
+static struct sql_result *
+driver_pgsql_transaction_commit_multi(struct pgsql_transaction_context *ctx)
+{
+	struct pgsql_db *db = (struct pgsql_db *)ctx->ctx.db;
+	struct sql_result *result;
+	struct sql_transaction_query *query;
+
+	result = driver_pgsql_sync_query(db, "BEGIN");
+	if (sql_result_next_row(result) < 0) {
+		commit_multi_fail(ctx, result, "BEGIN");
+		return NULL;
+	}
+	sql_result_unref(result);
+
+	/* send queries */
+	for (query = ctx->ctx.head; query != NULL; query = query->next) {
+		result = driver_pgsql_sync_query(db, query->query);
+		if (sql_result_next_row(result) < 0) {
+			commit_multi_fail(ctx, result, query->query);
+			break;
+		}
+		if (query->affected_rows != NULL) {
+			struct pgsql_result *pg_result =
+				(struct pgsql_result *)result;
+
+			if (str_to_uint(PQcmdTuples(pg_result->pgres),
+					query->affected_rows) < 0)
+				i_unreached();
+		}
+		sql_result_unref(result);
+	}
+
+	return driver_pgsql_sync_query(db, ctx->failed ?
+				       "ROLLBACK" : "COMMIT");
+}
+
+static void
+driver_pgsql_try_commit_s(struct pgsql_transaction_context *ctx,
+			  const char **error_r)
+{
+	struct sql_transaction_context *_ctx = &ctx->ctx;
+	struct pgsql_db *db = (struct pgsql_db *)_ctx->db;
+	struct sql_transaction_query *single_query = NULL;
+	struct sql_result *result;
+
+	if (_ctx->head->next == NULL) {
+		/* just a single query, send it */
+		single_query = _ctx->head;
+		result = sql_query_s(_ctx->db, single_query->query);
+	} else {
+		/* multiple queries, use a transaction */
+		driver_pgsql_sync_init(db);
+		result = driver_pgsql_transaction_commit_multi(ctx);
+		driver_pgsql_sync_deinit(db);
+	}
+
+	if (ctx->failed) {
+		i_assert(ctx->error != NULL);
+		e_debug(sql_transaction_finished_event(_ctx)->
+			add_str("error", ctx->error)->event(),
+			"Transaction failed: %s", ctx->error);
+		*error_r = ctx->error;
+	} else if (result != NULL) {
+		if (sql_result_next_row(result) < 0)
+			*error_r = sql_result_get_error(result);
+		else if (single_query != NULL &&
+			 single_query->affected_rows != NULL) {
+			struct pgsql_result *pg_result =
+				(struct pgsql_result *)result;
+
+			if (str_to_uint(PQcmdTuples(pg_result->pgres),
+					single_query->affected_rows) < 0)
+				i_unreached();
+		}
+	}
+
+	if (!ctx->failed) {
+		e_debug(sql_transaction_finished_event(_ctx)->event(),
+			"Transaction committed");
+	}
+
+	if (result != NULL)
+		sql_result_unref(result);
+}
+
+static int
+driver_pgsql_transaction_commit_s(struct sql_transaction_context *_ctx,
+				  const char **error_r)
+{
+	struct pgsql_transaction_context *ctx =
+		(struct pgsql_transaction_context *)_ctx;
+	struct pgsql_db *db = (struct pgsql_db *)_ctx->db;
+
+	*error_r = NULL;
+
+	if (_ctx->head != NULL) {
+		driver_pgsql_try_commit_s(ctx, error_r);
+		if (_ctx->db->state == SQL_DB_STATE_DISCONNECTED) {
+			*error_r = t_strdup(*error_r);
+			e_info(db->api.event, "Disconnected from database, "
+			       "retrying commit");
+			if (sql_connect(_ctx->db) >= 0) {
+				ctx->failed = FALSE;
+				*error_r = NULL;
+				driver_pgsql_try_commit_s(ctx, error_r);
+			}
+		}
+	}
+
+	driver_pgsql_transaction_free(ctx);
+	return *error_r == NULL ? 0 : -1;
+}
+
+static void
+driver_pgsql_transaction_rollback(struct sql_transaction_context *_ctx)
+{
+	struct pgsql_transaction_context *ctx =
+		(struct pgsql_transaction_context *)_ctx;
+	e_debug(sql_transaction_finished_event(_ctx)->
+			add_str("error", "Rolled back")->event(),
+		"Transaction rolled back");
+
+	driver_pgsql_transaction_free(ctx);
+}
+
+static void
+driver_pgsql_update(struct sql_transaction_context *_ctx, const char *query,
+		    unsigned int *affected_rows)
+{
+	struct pgsql_transaction_context *ctx =
+		(struct pgsql_transaction_context *)_ctx;
+
+	sql_transaction_add_query(_ctx, ctx->query_pool, query, affected_rows);
+}
+
+static const char *
+driver_pgsql_escape_blob(struct sql_db *_db ATTR_UNUSED,
+			 const unsigned char *data, size_t size)
+{
+	string_t *str = t_str_new(128);
+
+	str_append(str, "E'\\\\x");
+	binary_to_hex_append(str, data, size);
+	str_append_c(str, '\'');
+	return str_c(str);
+}
+
+static bool driver_pgsql_have_work(struct pgsql_db *db)
+{
+	return db->next_callback != NULL || db->pending_results != NULL ||
+		db->api.state == SQL_DB_STATE_CONNECTING;
+}
+
+static void driver_pgsql_wait(struct sql_db *_db)
+{
+	struct pgsql_db *db = (struct pgsql_db *)_db;
+
+	if (!driver_pgsql_have_work(db))
+		return;
+
+	struct ioloop *prev_ioloop = current_ioloop;
+	db->ioloop = io_loop_create();
+	db->io = io_loop_move_io(&db->io);
+	while (driver_pgsql_have_work(db))
+		io_loop_run(db->ioloop);
+
+	io_loop_set_current(prev_ioloop);
+	db->io = io_loop_move_io(&db->io);
+	io_loop_set_current(db->ioloop);
+	io_loop_destroy(&db->ioloop);
+}
+
+const struct sql_db driver_pgsql_db = {
+	.name = "pgsql",
+	.flags = SQL_DB_FLAG_POOLED,
+
+	.v = {
+		.get_flags = driver_pgsql_get_flags,
+		.init_full = driver_pgsql_init_full_v,
+		.deinit = driver_pgsql_deinit_v,
+		.connect = driver_pgsql_connect,
+		.disconnect = driver_pgsql_disconnect,
+		.escape_string = driver_pgsql_escape_string,
+		.exec = driver_pgsql_exec,
+		.query = driver_pgsql_query,
+		.query_s = driver_pgsql_query_s,
+		.wait = driver_pgsql_wait,
+
+		.transaction_begin = driver_pgsql_transaction_begin,
+		.transaction_commit = driver_pgsql_transaction_commit,
+		.transaction_commit_s = driver_pgsql_transaction_commit_s,
+		.transaction_rollback = driver_pgsql_transaction_rollback,
+
+		.update = driver_pgsql_update,
+
+		.escape_blob = driver_pgsql_escape_blob,
+	}
+};
+
+const struct sql_result driver_pgsql_result = {
+	.v = {
+		.free = driver_pgsql_result_free,
+		.next_row = driver_pgsql_result_next_row,
+		.get_fields_count = driver_pgsql_result_get_fields_count,
+		.get_field_name = driver_pgsql_result_get_field_name,
+		.find_field = driver_pgsql_result_find_field,
+		.get_field_value = driver_pgsql_result_get_field_value,
+		.get_field_value_binary = driver_pgsql_result_get_field_value_binary,
+		.find_field_value = driver_pgsql_result_find_field_value,
+		.get_values = driver_pgsql_result_get_values,
+		.get_error = driver_pgsql_result_get_error,
+	}
+};
+
+const char *driver_pgsql_version = DOVECOT_ABI_VERSION;
+
+void driver_pgsql_init(void);
+void driver_pgsql_deinit(void);
+
+void driver_pgsql_init(void)
+{
+	sql_driver_register(&driver_pgsql_db);
+}
+
+void driver_pgsql_deinit(void)
+{
+	sql_driver_unregister(&driver_pgsql_db);
+}
+
+#endif
diff --git a/src/lib-sql/driver-sqlite.c b/src/lib-sql/driver-sqlite.c
new file mode 100644
index 0000000..e05ed18
--- /dev/null
+++ b/src/lib-sql/driver-sqlite.c
@@ -0,0 +1,555 @@
+/* Copyright (c) 2006-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "array.h"
+#include "ioloop.h"
+#include "str.h"
+#include "hex-binary.h"
+#include "sql-api-private.h"
+
+#ifdef BUILD_SQLITE
+#include <sqlite3.h>
+
+/* retry time if db is busy (in ms) */
+static const int sqlite_busy_timeout = 1000;
+
+struct sqlite_db {
+	struct sql_db api;
+
+	pool_t pool;
+	const char *dbfile;
+	sqlite3 *sqlite;
+	bool connected:1;
+	int rc;
+};
+
+struct sqlite_result {
+	struct sql_result api;
+	sqlite3_stmt *stmt;
+	unsigned int cols;
+	const char **row;
+};
+
+struct sqlite_transaction_context {
+	struct sql_transaction_context ctx;
+	bool failed:1;
+};
+
+extern const struct sql_db driver_sqlite_db;
+extern const struct sql_result driver_sqlite_result;
+extern const struct sql_result driver_sqlite_error_result;
+
+static struct event_category event_category_sqlite = {
+	.parent = &event_category_sql,
+	.name = "sqlite"
+};
+
+static int driver_sqlite_connect(struct sql_db *_db)
+{
+ 	struct sqlite_db *db = (struct sqlite_db *)_db;
+
+	if (db->connected)
+		return 1;
+
+	db->rc = sqlite3_open(db->dbfile, &db->sqlite);
+
+	if (db->rc == SQLITE_OK) {
+		db->connected = TRUE;
+		sqlite3_busy_timeout(db->sqlite, sqlite_busy_timeout);
+		return 1;
+	} else {
+		e_error(_db->event, "open(%s) failed: %s", db->dbfile,
+			sqlite3_errmsg(db->sqlite));
+		sqlite3_close(db->sqlite);
+		db->sqlite = NULL;
+		return -1;
+	}
+}
+
+static void driver_sqlite_disconnect(struct sql_db *_db)
+{
+ 	struct sqlite_db *db = (struct sqlite_db *)_db;
+
+	sqlite3_close(db->sqlite);
+	db->sqlite = NULL;
+}
+
+static int driver_sqlite_init_full_v(const struct sql_settings *set, struct sql_db **db_r,
+				     const char **error_r ATTR_UNUSED)
+{
+	struct sqlite_db *db;
+	pool_t pool;
+
+	pool = pool_alloconly_create("sqlite driver", 512);
+	db = p_new(pool, struct sqlite_db, 1);
+	db->pool = pool;
+	db->api = driver_sqlite_db;
+	db->dbfile = p_strdup(db->pool, set->connect_string);
+	db->connected = FALSE;
+	db->api.event = event_create(set->event_parent);
+	event_add_category(db->api.event, &event_category_sqlite);
+	event_set_append_log_prefix(db->api.event, "sqlite: ");
+
+	*db_r = &db->api;
+	return 0;
+}
+
+static void driver_sqlite_deinit_v(struct sql_db *_db)
+{
+	struct sqlite_db *db = (struct sqlite_db *)_db;
+
+	_db->no_reconnect = TRUE;
+	sql_db_set_state(&db->api, SQL_DB_STATE_DISCONNECTED);
+
+	sqlite3_close(db->sqlite);
+	sql_connection_log_finished(_db);
+	event_unref(&_db->event);
+	array_free(&_db->module_contexts);
+	pool_unref(&db->pool);
+}
+
+static const char *
+driver_sqlite_escape_string(struct sql_db *_db ATTR_UNUSED,
+			    const char *string)
+{
+	const char *p;
+	char *dest, *destbegin;
+
+	/* find the first ' */
+	for (p = string; *p != '\''; p++) {
+		if (*p == '\0')
+			return t_strdup_noconst(string);
+	}
+
+	/* @UNSAFE: escape ' with '' */
+	dest = destbegin = t_buffer_get((p - string) + strlen(string) * 2 + 1);
+
+	memcpy(dest, string, p - string);
+	dest += p - string;
+
+	for (; *p != '\0'; p++) {
+		*dest++ = *p;
+		if (*p == '\'')
+			*dest++ = *p;
+	}
+	*dest++ = '\0';
+	t_buffer_alloc(dest - destbegin);
+
+	return destbegin;
+}
+
+static void driver_sqlite_result_log(const struct sql_result *result, const char *query)
+{
+	struct sqlite_db *db = (struct sqlite_db *)result->db;
+	bool success = db->connected && db->rc == SQLITE_OK;
+	int duration;
+	const char *suffix = "";
+	struct event_passthrough *e =
+		sql_query_finished_event(&db->api, result->event, query, success,
+					 &duration);
+	io_loop_time_refresh();
+
+	if (!db->connected) {
+		suffix = ": Cannot connect to database";
+		e->add_str("error", "Cannot connect to database");
+	} else if (db->rc != SQLITE_OK) {
+		suffix = t_strdup_printf(": %s (%d)", sqlite3_errmsg(db->sqlite),
+					 db->rc);
+		e->add_str("error", sqlite3_errmsg(db->sqlite));
+		e->add_int("error_code", db->rc);
+	}
+
+	e_debug(e->event(), SQL_QUERY_FINISHED_FMT"%s", query, duration, suffix);
+}
+
+static void driver_sqlite_exec(struct sql_db *_db, const char *query)
+{
+	struct sqlite_db *db = (struct sqlite_db *)_db;
+	struct sql_result result;
+
+	i_zero(&result);
+	result.db = _db;
+	result.event = event_create(_db->event);
+
+	/* Other drivers do not include time spent connecting
+	   but this simplifies error logging, so we include
+	   it here. */
+	if (driver_sqlite_connect(_db) < 0) {
+		driver_sqlite_result_log(&result, query);
+	} else {
+		db->rc = sqlite3_exec(db->sqlite, query, NULL, NULL, NULL);
+		driver_sqlite_result_log(&result, query);
+	}
+
+	event_unref(&result.event);
+}
+
+static void driver_sqlite_query(struct sql_db *db, const char *query,
+				sql_query_callback_t *callback, void *context)
+{
+	struct sql_result *result;
+
+	result = sql_query_s(db, query);
+	result->callback = TRUE;
+	callback(result, context);
+	result->callback = FALSE;
+	sql_result_unref(result);
+}
+
+static struct sql_result *
+driver_sqlite_query_s(struct sql_db *_db, const char *query)
+{
+	struct sqlite_db *db = (struct sqlite_db *)_db;
+	struct sqlite_result *result;
+	struct event *event;
+
+	result = i_new(struct sqlite_result, 1);
+	result->api.db = _db;
+	/* Temporarily store the event since result->api gets
+	 * overwritten later here and we need to reset it. */
+	event = event_create(_db->event);
+	result->api.event = event;
+
+	if (driver_sqlite_connect(_db) < 0) {
+		driver_sqlite_result_log(&result->api, query);
+		result->api = driver_sqlite_error_result;
+		result->stmt = NULL;
+		result->cols = 0;
+	} else {
+		db->rc = sqlite3_prepare(db->sqlite, query, -1, &result->stmt, NULL);
+		driver_sqlite_result_log(&result->api, query);
+		if (db->rc == SQLITE_OK) {
+			result->api = driver_sqlite_result;
+			result->cols = sqlite3_column_count(result->stmt);
+			result->row = i_new(const char *, result->cols);
+		} else {
+			result->api = driver_sqlite_error_result;
+			result->stmt = NULL;
+			result->cols = 0;
+		}
+	}
+
+	result->api.db = _db;
+	result->api.refcount = 1;
+	result->api.event = event;
+	return &result->api;
+}
+
+static void driver_sqlite_result_free(struct sql_result *_result)
+{
+	struct sqlite_result *result = (struct sqlite_result *)_result;
+	struct sqlite_db *db = (struct sqlite_db *)	result->api.db;
+	int rc;
+
+	if (_result->callback)
+		return;
+
+	if (result->stmt != NULL) {
+		if ((rc = sqlite3_finalize(result->stmt)) != SQLITE_OK) {
+			e_warning(_result->event, "finalize failed: %s (%d)",
+				  sqlite3_errmsg(db->sqlite), rc);
+		}
+		i_free(result->row);
+	}
+	event_unref(&result->api.event);
+	i_free(result);
+}
+
+static int driver_sqlite_result_next_row(struct sql_result *_result)
+{
+	struct sqlite_result *result = (struct sqlite_result *)_result;
+
+	switch (sqlite3_step(result->stmt)) {
+	case SQLITE_ROW:
+		return 1;
+	case SQLITE_DONE:
+		return 0;
+	default:
+		return -1;
+	}
+}
+
+static unsigned int
+driver_sqlite_result_get_fields_count(struct sql_result *_result)
+{
+	struct sqlite_result *result = (struct sqlite_result *)_result;
+
+	return result->cols;
+}
+
+static const char *
+driver_sqlite_result_get_field_name(struct sql_result *_result,
+				    unsigned int idx)
+{
+	struct sqlite_result *result = (struct sqlite_result *)_result;
+
+	return sqlite3_column_name(result->stmt, idx);
+}
+
+static int driver_sqlite_result_find_field(struct sql_result *_result,
+					   const char *field_name)
+{
+	struct sqlite_result *result = (struct sqlite_result *)_result;
+	unsigned int i;
+
+	for (i = 0; i < result->cols; ++i) {
+		const char *col = sqlite3_column_name(result->stmt, i);
+
+		if (strcmp(col, field_name) == 0)
+			return i;
+	}
+
+	return -1;
+}
+
+static const char *
+driver_sqlite_result_get_field_value(struct sql_result *_result,
+				     unsigned int idx)
+{
+	struct sqlite_result *result = (struct sqlite_result *)_result;
+
+	return (const char*)sqlite3_column_text(result->stmt, idx);
+}
+
+static const unsigned char *
+driver_sqlite_result_get_field_value_binary(struct sql_result *_result,
+					    unsigned int idx, size_t *size_r)
+{
+	struct sqlite_result *result = (struct sqlite_result *)_result;
+
+	*size_r = sqlite3_column_bytes(result->stmt, idx);
+	return sqlite3_column_blob(result->stmt, idx);
+}
+
+static const char *
+driver_sqlite_result_find_field_value(struct sql_result *result,
+				     const char *field_name)
+{
+	int idx;
+
+	idx = driver_sqlite_result_find_field(result, field_name);
+	if (idx < 0)
+		return NULL;
+	return driver_sqlite_result_get_field_value(result, idx);
+}
+
+static const char *const *
+driver_sqlite_result_get_values(struct sql_result *_result)
+{
+	struct sqlite_result *result = (struct sqlite_result *)_result;
+	unsigned int i;
+
+	for (i = 0; i < result->cols; ++i) {
+		result->row[i] =
+			driver_sqlite_result_get_field_value(_result, i);
+	}
+
+	return (const char *const *)result->row;
+}
+
+static const char *driver_sqlite_result_get_error(struct sql_result *_result)
+{
+	struct sqlite_result *result = (struct sqlite_result *)_result;
+	struct sqlite_db *db = (struct sqlite_db *)result->api.db;
+
+	if (db->connected)
+		return sqlite3_errmsg(db->sqlite);
+	else
+		return "Cannot connect to database";
+}
+
+static struct sql_transaction_context *
+driver_sqlite_transaction_begin(struct sql_db *_db)
+{
+	struct sqlite_transaction_context *ctx;
+	struct sqlite_db *db = (struct sqlite_db *)_db;
+
+	ctx = i_new(struct sqlite_transaction_context, 1);
+	ctx->ctx.db = _db;
+	ctx->ctx.event = event_create(_db->event);
+
+	sql_exec(_db, "BEGIN TRANSACTION");
+	if (db->rc != SQLITE_OK)
+		ctx->failed = TRUE;
+
+	return &ctx->ctx;
+}
+
+static void
+driver_sqlite_transaction_rollback(struct sql_transaction_context *_ctx)
+{
+	struct sqlite_transaction_context *ctx =
+		(struct sqlite_transaction_context *)_ctx;
+
+	if (!ctx->failed) {
+		e_debug(sql_transaction_finished_event(_ctx)->
+			add_str("error", "Rolled back")->event(),
+			"Transaction rolled back");
+	}
+	sql_exec(_ctx->db, "ROLLBACK");
+	event_unref(&_ctx->event);
+	i_free(ctx);
+}
+
+static void
+driver_sqlite_transaction_commit(struct sql_transaction_context *_ctx,
+				 sql_commit_callback_t *callback, void *context)
+{
+	struct sqlite_transaction_context *ctx =
+		(struct sqlite_transaction_context *)_ctx;
+	struct sqlite_db *db = (struct sqlite_db *)ctx->ctx.db;
+	struct sql_commit_result commit_result;
+
+	if (!ctx->failed) {
+		sql_exec(_ctx->db, "COMMIT");
+		if (db->rc != SQLITE_OK)
+			ctx->failed = TRUE;
+	}
+
+	i_zero(&commit_result);
+	if (ctx->failed) {
+		commit_result.error = sqlite3_errmsg(db->sqlite);
+		callback(&commit_result, context);
+		e_debug(sql_transaction_finished_event(_ctx)->
+			add_str("error", commit_result.error)->event(),
+			"Transaction failed");
+		/* From SQLite manual: It is recommended that applications
+		   respond to the errors listed above by explicitly issuing a
+		   ROLLBACK command. If the transaction has already been rolled
+		   back automatically by the error response, then the ROLLBACK
+		   command will fail with an error, but no harm is caused by
+		   this. */
+		driver_sqlite_transaction_rollback(_ctx);
+	} else {
+		e_debug(sql_transaction_finished_event(_ctx)->event(),
+			"Transaction committed");
+		callback(&commit_result, context);
+		event_unref(&_ctx->event);
+		i_free(ctx);
+	}
+}
+
+static int
+driver_sqlite_transaction_commit_s(struct sql_transaction_context *_ctx,
+				   const char **error_r)
+{
+	struct sqlite_transaction_context *ctx =
+		(struct sqlite_transaction_context *)_ctx;
+	struct sqlite_db *db = (struct sqlite_db *) ctx->ctx.db;
+
+	if (ctx->failed) {
+		/* also does i_free(ctx) */
+		driver_sqlite_transaction_rollback(_ctx);
+		return -1;
+	}
+
+	sql_exec(_ctx->db, "COMMIT");
+	*error_r = sqlite3_errmsg(db->sqlite);
+	i_free(ctx);
+	return 0;
+}
+
+static void
+driver_sqlite_update(struct sql_transaction_context *_ctx, const char *query,
+		     unsigned int *affected_rows)
+{
+	struct sqlite_transaction_context *ctx =
+		(struct sqlite_transaction_context *)_ctx;
+	struct sqlite_db *db = (struct sqlite_db *)ctx->ctx.db;
+
+	if (ctx->failed)
+		return;
+
+	sql_exec(_ctx->db, query);
+	if (db->rc != SQLITE_OK)
+		ctx->failed = TRUE;
+	else if (affected_rows != NULL)
+		*affected_rows = sqlite3_changes(db->sqlite);
+}
+
+static const char *
+driver_sqlite_escape_blob(struct sql_db *_db ATTR_UNUSED,
+			  const unsigned char *data, size_t size)
+{
+	string_t *str = t_str_new(128);
+
+	str_append(str, "x'");
+	binary_to_hex_append(str, data, size);
+	str_append_c(str, '\'');
+	return str_c(str);
+}
+
+const struct sql_db driver_sqlite_db = {
+	.name = "sqlite",
+	.flags =
+#if SQLITE_VERSION_NUMBER >= 3024000
+		SQL_DB_FLAG_ON_CONFLICT_DO |
+#endif
+		SQL_DB_FLAG_BLOCKING,
+
+	.v = {
+		.init_full = driver_sqlite_init_full_v,
+		.deinit = driver_sqlite_deinit_v,
+		.connect = driver_sqlite_connect,
+		.disconnect = driver_sqlite_disconnect,
+		.escape_string = driver_sqlite_escape_string,
+		.exec = driver_sqlite_exec,
+		.query = driver_sqlite_query,
+		.query_s = driver_sqlite_query_s,
+
+		.transaction_begin = driver_sqlite_transaction_begin,
+		.transaction_commit = driver_sqlite_transaction_commit,
+		.transaction_commit_s = driver_sqlite_transaction_commit_s,
+		.transaction_rollback = driver_sqlite_transaction_rollback,
+
+		.update = driver_sqlite_update,
+
+		.escape_blob = driver_sqlite_escape_blob,
+	}
+};
+
+const struct sql_result driver_sqlite_result = {
+	.v = {
+		.free = driver_sqlite_result_free,
+		.next_row = driver_sqlite_result_next_row,
+		.get_fields_count = driver_sqlite_result_get_fields_count,
+		.get_field_name = driver_sqlite_result_get_field_name,
+		.find_field = driver_sqlite_result_find_field,
+		.get_field_value = driver_sqlite_result_get_field_value,
+		.get_field_value_binary = driver_sqlite_result_get_field_value_binary,
+		.find_field_value = driver_sqlite_result_find_field_value,
+		.get_values = driver_sqlite_result_get_values,
+		.get_error = driver_sqlite_result_get_error,
+	}
+};
+
+static int
+driver_sqlite_result_error_next_row(struct sql_result *result ATTR_UNUSED)
+{
+	return -1;
+}
+
+const struct sql_result driver_sqlite_error_result = {
+	.v = {
+		.free = driver_sqlite_result_free,
+		.next_row = driver_sqlite_result_error_next_row,
+		.get_error = driver_sqlite_result_get_error,
+	}
+};
+
+const char *driver_sqlite_version = DOVECOT_ABI_VERSION;
+
+void driver_sqlite_init(void);
+void driver_sqlite_deinit(void);
+
+void driver_sqlite_init(void)
+{
+	sql_driver_register(&driver_sqlite_db);
+}
+
+void driver_sqlite_deinit(void)
+{
+	sql_driver_unregister(&driver_sqlite_db);
+}
+
+#endif
diff --git a/src/lib-sql/driver-sqlpool.c b/src/lib-sql/driver-sqlpool.c
new file mode 100644
index 0000000..553b2a0
--- /dev/null
+++ b/src/lib-sql/driver-sqlpool.c
@@ -0,0 +1,934 @@
+/* Copyright (c) 2010-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "array.h"
+#include "llist.h"
+#include "ioloop.h"
+#include "sql-api-private.h"
+
+#include <time.h>
+
+#define QUERY_TIMEOUT_SECS 6
+
+/* sqlpool events are separate from category:sql, because
+   they are usually not very interesting, and would only
+   make logging too noisy. They can be enabled explicitly.
+*/
+static struct event_category event_category_sqlpool = {
+	.name = "sqlpool",
+};
+
+struct sqlpool_host {
+	char *connect_string;
+
+	unsigned int connection_count;
+};
+
+struct sqlpool_connection {
+	struct sql_db *db;
+	unsigned int host_idx;
+};
+
+struct sqlpool_db {
+	struct sql_db api;
+
+	pool_t pool;
+	const struct sql_db *driver;
+	unsigned int connection_limit;
+
+	ARRAY(struct sqlpool_host) hosts;
+	/* all connections from all hosts */
+	ARRAY(struct sqlpool_connection) all_connections;
+	/* index of last connection in all_connections that was used to
+	   send a query. */
+	unsigned int last_query_conn_idx;
+
+	/* queued requests */
+	struct sqlpool_request *requests_head, *requests_tail;
+	struct timeout *request_to;
+};
+
+struct sqlpool_request {
+	struct sqlpool_request *prev, *next;
+
+	struct sqlpool_db *db;
+	time_t created;
+
+	unsigned int host_idx;
+	unsigned int retry_count;
+
+	struct event *event;
+
+	/* requests are a) queries */
+	char *query;
+	sql_query_callback_t *callback;
+	void *context;
+
+	/* b) transaction waiters */
+	struct sqlpool_transaction_context *trans;
+};
+
+struct sqlpool_transaction_context {
+	struct sql_transaction_context ctx;
+
+	sql_commit_callback_t *callback;
+	void *context;
+
+	pool_t query_pool;
+	struct sqlpool_request *commit_request;
+};
+
+extern struct sql_db driver_sqlpool_db;
+
+static struct sqlpool_connection *
+sqlpool_add_connection(struct sqlpool_db *db, struct sqlpool_host *host,
+		       unsigned int host_idx);
+static void
+driver_sqlpool_query_callback(struct sql_result *result,
+			      struct sqlpool_request *request);
+static void
+driver_sqlpool_commit_callback(const struct sql_commit_result *result,
+			       struct sqlpool_transaction_context *ctx);
+static void driver_sqlpool_deinit(struct sql_db *_db);
+
+static struct sqlpool_request * ATTR_NULL(2)
+sqlpool_request_new(struct sqlpool_db *db, const char *query)
+{
+	struct sqlpool_request *request;
+
+	request = i_new(struct sqlpool_request, 1);
+	request->db = db;
+	request->created = time(NULL);
+	request->query = i_strdup(query);
+	request->event = event_create(db->api.event);
+	return request;
+}
+
+static void
+sqlpool_request_free(struct sqlpool_request **_request)
+{
+	struct sqlpool_request *request = *_request;
+
+	*_request = NULL;
+
+	i_assert(request->prev == NULL && request->next == NULL);
+	event_unref(&request->event);
+	i_free(request->query);
+	i_free(request);
+}
+
+static void
+sqlpool_request_abort(struct sqlpool_request **_request)
+{
+	struct sqlpool_request *request = *_request;
+
+	*_request = NULL;
+
+	if (request->callback != NULL)
+		request->callback(&sql_not_connected_result, request->context);
+
+	i_assert(request->prev != NULL ||
+		 request->db->requests_head == request);
+	DLLIST2_REMOVE(&request->db->requests_head,
+		       &request->db->requests_tail, request);
+	sqlpool_request_free(&request);
+}
+
+static struct sql_transaction_context *
+driver_sqlpool_new_conn_trans(struct sqlpool_transaction_context *trans,
+			      struct sql_db *conndb)
+{
+	struct sql_transaction_context *conn_trans;
+	struct sql_transaction_query *query;
+
+	conn_trans = sql_transaction_begin(conndb);
+	/* backend will use our queries list (we might still append more
+	   queries to the list) */
+	conn_trans->head = trans->ctx.head;
+	conn_trans->tail = trans->ctx.tail;
+	for (query = conn_trans->head; query != NULL; query = query->next)
+		query->trans = conn_trans;
+	return conn_trans;
+}
+
+static void
+sqlpool_request_handle_transaction(struct sql_db *conndb,
+				   struct sqlpool_transaction_context *trans)
+{
+	struct sql_transaction_context *conn_trans;
+
+	sqlpool_request_free(&trans->commit_request);
+	conn_trans = driver_sqlpool_new_conn_trans(trans, conndb);
+	sql_transaction_commit(&conn_trans,
+			       driver_sqlpool_commit_callback, trans);
+}
+
+static void
+sqlpool_request_send_next(struct sqlpool_db *db, struct sql_db *conndb)
+{
+	struct sqlpool_request *request;
+
+	if (db->requests_head == NULL || !SQL_DB_IS_READY(conndb))
+		return;
+
+	request = db->requests_head;
+	DLLIST2_REMOVE(&db->requests_head, &db->requests_tail, request);
+	timeout_reset(db->request_to);
+
+	if (request->query != NULL) {
+		sql_query(conndb, request->query,
+			  driver_sqlpool_query_callback, request);
+	} else if (request->trans != NULL) {
+		sqlpool_request_handle_transaction(conndb, request->trans);
+	} else {
+		i_unreached();
+	}
+}
+
+static void sqlpool_reconnect(struct sql_db *conndb)
+{
+	timeout_remove(&conndb->to_reconnect);
+	(void)sql_connect(conndb);
+}
+
+static struct sqlpool_host *
+sqlpool_find_host_with_least_connections(struct sqlpool_db *db,
+					 unsigned int *host_idx_r)
+{
+	struct sqlpool_host *hosts, *min = NULL;
+	unsigned int i, count;
+
+	hosts = array_get_modifiable(&db->hosts, &count);
+	i_assert(count > 0);
+
+	min = &hosts[0];
+	*host_idx_r = 0;
+
+	for (i = 1; i < count; i++) {
+		if (min->connection_count > hosts[i].connection_count) {
+			min = &hosts[i];
+			*host_idx_r = i;
+		}
+	}
+	return min;
+}
+
+static bool sqlpool_have_successful_connections(struct sqlpool_db *db)
+{
+	const struct sqlpool_connection *conn;
+
+	array_foreach(&db->all_connections, conn) {
+		if (conn->db->state >= SQL_DB_STATE_IDLE)
+			return TRUE;
+	}
+	return FALSE;
+}
+
+static void
+sqlpool_handle_connect_failed(struct sqlpool_db *db, struct sql_db *conndb)
+{
+	struct sqlpool_host *host;
+	unsigned int host_idx;
+
+	if (conndb->connect_failure_count > 0) {
+		/* increase delay between reconnections to this
+		   server */
+		conndb->connect_delay *= 5;
+		if (conndb->connect_delay > SQL_CONNECT_MAX_DELAY)
+			conndb->connect_delay = SQL_CONNECT_MAX_DELAY;
+	}
+	conndb->connect_failure_count++;
+
+	/* reconnect after the delay */
+	timeout_remove(&conndb->to_reconnect);
+	conndb->to_reconnect = timeout_add(conndb->connect_delay * 1000,
+					   sqlpool_reconnect, conndb);
+
+	/* if we have zero successful hosts and there still are hosts
+	   without connections, connect to one of them. */
+	if (!sqlpool_have_successful_connections(db)) {
+		host = sqlpool_find_host_with_least_connections(db, &host_idx);
+		if (host->connection_count == 0)
+			(void)sqlpool_add_connection(db, host, host_idx);
+	}
+}
+
+static void
+sqlpool_state_changed(struct sql_db *conndb, enum sql_db_state prev_state,
+		      void *context)
+{
+	struct sqlpool_db *db = context;
+
+	if (conndb->state == SQL_DB_STATE_IDLE) {
+		conndb->connect_failure_count = 0;
+		conndb->connect_delay = SQL_CONNECT_MIN_DELAY;
+		sqlpool_request_send_next(db, conndb);
+	}
+
+	if (prev_state == SQL_DB_STATE_CONNECTING &&
+	    conndb->state == SQL_DB_STATE_DISCONNECTED &&
+	    !conndb->no_reconnect)
+		sqlpool_handle_connect_failed(db, conndb);
+}
+
+static struct sqlpool_connection *
+sqlpool_add_connection(struct sqlpool_db *db, struct sqlpool_host *host,
+		       unsigned int host_idx)
+{
+	struct sql_db *conndb;
+	struct sqlpool_connection *conn;
+	const char *error;
+	int ret = 0;
+
+	host->connection_count++;
+
+	e_debug(db->api.event, "Creating new connection");
+
+	if (db->driver->v.init_full == NULL) {
+		conndb = db->driver->v.init(host->connect_string);
+	} else {
+		struct sql_settings set = {
+			.connect_string = host->connect_string,
+			.event_parent = event_get_parent(db->api.event),
+		};
+		ret = db->driver->v.init_full(&set, &conndb, &error);
+	}
+	if (ret < 0)
+		i_fatal("sqlpool: %s", error);
+
+	sql_init_common(conndb);
+
+	conndb->state_change_callback = sqlpool_state_changed;
+	conndb->state_change_context = db;
+	conndb->connect_delay = SQL_CONNECT_MIN_DELAY;
+
+	conn = array_append_space(&db->all_connections);
+	conn->host_idx = host_idx;
+	conn->db = conndb;
+	return conn;
+}
+
+static struct sqlpool_connection *
+sqlpool_add_new_connection(struct sqlpool_db *db)
+{
+	struct sqlpool_host *host;
+	unsigned int host_idx;
+
+	host = sqlpool_find_host_with_least_connections(db, &host_idx);
+	if (host->connection_count >= db->connection_limit)
+		return NULL;
+	else
+		return sqlpool_add_connection(db, host, host_idx);
+}
+
+static const struct sqlpool_connection *
+sqlpool_find_available_connection(struct sqlpool_db *db,
+				  unsigned int unwanted_host_idx,
+				  bool *all_disconnected_r)
+{
+	const struct sqlpool_connection *conns;
+	unsigned int i, count;
+
+	*all_disconnected_r = TRUE;
+
+	conns = array_get(&db->all_connections, &count);
+	for (i = 0; i < count; i++) {
+		unsigned int idx = (i + db->last_query_conn_idx + 1) % count;
+		struct sql_db *conndb = conns[idx].db;
+
+		if (conns[idx].host_idx == unwanted_host_idx)
+			continue;
+
+		if (!SQL_DB_IS_READY(conndb) && conndb->to_reconnect == NULL) {
+			/* see if we could reconnect to it immediately */
+			(void)sql_connect(conndb);
+		}
+		if (SQL_DB_IS_READY(conndb)) {
+			db->last_query_conn_idx = idx;
+			*all_disconnected_r = FALSE;
+			return &conns[idx];
+		}
+		if (conndb->state != SQL_DB_STATE_DISCONNECTED)
+			*all_disconnected_r = FALSE;
+	}
+	return NULL;
+}
+
+static bool
+driver_sqlpool_get_connection(struct sqlpool_db *db,
+			      unsigned int unwanted_host_idx,
+			      const struct sqlpool_connection **conn_r)
+{
+	const struct sqlpool_connection *conn, *conns;
+	unsigned int i, count;
+	bool all_disconnected;
+
+	conn = sqlpool_find_available_connection(db, unwanted_host_idx,
+						 &all_disconnected);
+	if (conn == NULL && unwanted_host_idx != UINT_MAX) {
+		/* maybe there are no wanted hosts. use any of them. */
+		conn = sqlpool_find_available_connection(db, UINT_MAX,
+							 &all_disconnected);
+	}
+	if (conn == NULL && all_disconnected) {
+		/* no connected connections. connect_delays may have gotten too
+		   high, reset all of them to see if some are still alive. */
+		conns = array_get(&db->all_connections, &count);
+		for (i = 0; i < count; i++) {
+			struct sql_db *conndb = conns[i].db;
+
+			if (conndb->connect_delay > SQL_CONNECT_RESET_DELAY)
+				conndb->connect_delay = SQL_CONNECT_RESET_DELAY;
+		}
+		conn = sqlpool_find_available_connection(db, UINT_MAX,
+							 &all_disconnected);
+	}
+	if (conn == NULL) {
+		/* still nothing. try creating new connections */
+		conn = sqlpool_add_new_connection(db);
+		if (conn != NULL)
+			(void)sql_connect(conn->db);
+		if (conn == NULL || !SQL_DB_IS_READY(conn->db))
+			return FALSE;
+	}
+	*conn_r = conn;
+	return TRUE;
+}
+
+static bool
+driver_sqlpool_get_sync_connection(struct sqlpool_db *db,
+				   const struct sqlpool_connection **conn_r)
+{
+	const struct sqlpool_connection *conns;
+	unsigned int i, count;
+
+	if (driver_sqlpool_get_connection(db, UINT_MAX, conn_r))
+		return TRUE;
+
+	/* no idling connections, but maybe we can find one that's trying to
+	   connect to server, and we can use it once it's finished */
+	conns = array_get(&db->all_connections, &count);
+	for (i = 0; i < count; i++) {
+		if (conns[i].db->state == SQL_DB_STATE_CONNECTING) {
+			*conn_r = &conns[i];
+			return TRUE;
+		}
+	}
+	return FALSE;
+}
+
+static bool
+driver_sqlpool_get_connected_flags(struct sqlpool_db *db,
+				   enum sql_db_flags *flags_r)
+{
+	const struct sqlpool_connection *conn;
+
+	array_foreach(&db->all_connections, conn) {
+		if (conn->db->state > SQL_DB_STATE_CONNECTING) {
+			*flags_r = sql_get_flags(conn->db);
+			return TRUE;
+		}
+	}
+	return FALSE;
+}
+
+static enum sql_db_flags driver_sqlpool_get_flags(struct sql_db *_db)
+{
+	struct sqlpool_db *db = (struct sqlpool_db *)_db;
+	const struct sqlpool_connection *conn;
+	enum sql_db_flags flags;
+
+	/* try to use a connected db */
+	if (driver_sqlpool_get_connected_flags(db, &flags))
+		return flags;
+
+	if (!driver_sqlpool_get_sync_connection(db, &conn)) {
+		/* Failed to connect to database. Just use the first
+		   connection. */
+		conn = array_idx(&db->all_connections, 0);
+	}
+	return sql_get_flags(conn->db);
+}
+
+static int
+driver_sqlpool_parse_hosts(struct sqlpool_db *db, const char *connect_string,
+			   const char **error_r)
+{
+	const char *const *args, *key, *value, *hostname;
+	struct sqlpool_host *host;
+	ARRAY_TYPE(const_string) hostnames, connect_args;
+
+	t_array_init(&hostnames, 8);
+	t_array_init(&connect_args, 32);
+
+	/* connect string is a space separated list. it may contain
+	   backend-specific strings which we'll pass as-is. we'll only care
+	   about our own settings, plus the host settings. */
+	args = t_strsplit_spaces(connect_string, " ");
+	for (; *args != NULL; args++) {
+		value = strchr(*args, '=');
+		if (value == NULL) {
+			key = *args;
+			value = "";
+		} else {
+			key = t_strdup_until(*args, value);
+			value++;
+		}
+
+		if (strcmp(key, "maxconns") == 0) {
+			if (str_to_uint(value, &db->connection_limit) < 0) {
+				*error_r = t_strdup_printf("Invalid value for maxconns: %s",
+					value);
+				return -1;
+			}
+		} else if (strcmp(key, "host") == 0) {
+			array_push_back(&hostnames, &value);
+		} else {
+			array_push_back(&connect_args, args);
+		}
+	}
+
+	/* build a new connect string without our settings or hosts */
+	array_append_zero(&connect_args);
+	connect_string = t_strarray_join(array_front(&connect_args), " ");
+
+	if (array_count(&hostnames) == 0) {
+		/* no hosts specified. create a default one. */
+		host = array_append_space(&db->hosts);
+		host->connect_string = i_strdup(connect_string);
+	} else {
+		if (*connect_string == '\0')
+			connect_string = NULL;
+
+		array_foreach_elem(&hostnames, hostname) {
+			host = array_append_space(&db->hosts);
+			host->connect_string =
+				i_strconcat("host=", hostname, " ",
+					    connect_string, NULL);
+		}
+	}
+
+	if (db->connection_limit == 0)
+		db->connection_limit = SQL_DEFAULT_CONNECTION_LIMIT;
+	return 0;
+}
+
+static void sqlpool_add_all_once(struct sqlpool_db *db)
+{
+	struct sqlpool_host *host;
+	unsigned int host_idx;
+
+	for (;;) {
+		host = sqlpool_find_host_with_least_connections(db, &host_idx);
+		if (host->connection_count > 0)
+			break;
+		(void)sqlpool_add_connection(db, host, host_idx);
+	}
+}
+
+int driver_sqlpool_init_full(const struct sql_settings *set, const struct sql_db *driver,
+			     struct sql_db **db_r, const char **error_r)
+{
+	struct sqlpool_db *db;
+	int ret;
+
+	db = i_new(struct sqlpool_db, 1);
+	db->driver = driver;
+	db->api = driver_sqlpool_db;
+	db->api.flags = driver->flags;
+	db->api.event = event_create(set->event_parent);
+	event_add_category(db->api.event, &event_category_sqlpool);
+	event_set_append_log_prefix(db->api.event,
+				    t_strdup_printf("sqlpool(%s): ", driver->name));
+	i_array_init(&db->hosts, 8);
+
+	T_BEGIN {
+		ret = driver_sqlpool_parse_hosts(db, set->connect_string,
+						 error_r);
+	} T_END_PASS_STR_IF(ret < 0, error_r);
+
+	if (ret < 0) {
+		driver_sqlpool_deinit(&db->api);
+		return ret;
+	}
+	i_array_init(&db->all_connections, 16);
+	/* connect to all databases so we can do load balancing immediately */
+	sqlpool_add_all_once(db);
+
+	*db_r = &db->api;
+	return 0;
+}
+
+static void driver_sqlpool_abort_requests(struct sqlpool_db *db)
+{
+	while (db->requests_head != NULL) {
+		struct sqlpool_request *request = db->requests_head;
+
+		sqlpool_request_abort(&request);
+	}
+	timeout_remove(&db->request_to);
+}
+
+static void driver_sqlpool_deinit(struct sql_db *_db)
+{
+	struct sqlpool_db *db = (struct sqlpool_db *)_db;
+	struct sqlpool_host *host;
+	struct sqlpool_connection *conn;
+
+	array_foreach_modifiable(&db->all_connections, conn)
+		sql_unref(&conn->db);
+	array_clear(&db->all_connections);
+
+	driver_sqlpool_abort_requests(db);
+
+	array_foreach_modifiable(&db->hosts, host)
+		i_free(host->connect_string);
+
+	i_assert(array_count(&db->all_connections) == 0);
+	array_free(&db->hosts);
+	array_free(&db->all_connections);
+	array_free(&_db->module_contexts);
+	event_unref(&_db->event);
+	i_free(db);
+}
+
+static int driver_sqlpool_connect(struct sql_db *_db)
+{
+	struct sqlpool_db *db = (struct sqlpool_db *)_db;
+	const struct sqlpool_connection *conn;
+	int ret = -1, ret2;
+
+	array_foreach(&db->all_connections, conn) {
+		ret2 = conn->db->to_reconnect != NULL ? -1 :
+			sql_connect(conn->db);
+		if (ret2 > 0)
+			ret = 1;
+		else if (ret2 == 0 && ret < 0)
+			ret = 0;
+	}
+	return ret;
+}
+
+static void driver_sqlpool_disconnect(struct sql_db *_db)
+{
+	struct sqlpool_db *db = (struct sqlpool_db *)_db;
+	const struct sqlpool_connection *conn;
+
+	array_foreach(&db->all_connections, conn)
+		sql_disconnect(conn->db);
+	driver_sqlpool_abort_requests(db);
+}
+
+static const char *
+driver_sqlpool_escape_string(struct sql_db *_db, const char *string)
+{
+	struct sqlpool_db *db = (struct sqlpool_db *)_db;
+	const struct sqlpool_connection *conns;
+	unsigned int i, count;
+
+	/* use the first ready connection */
+	conns = array_get(&db->all_connections, &count);
+	for (i = 0; i < count; i++) {
+		if (SQL_DB_IS_READY(conns[i].db))
+			return sql_escape_string(conns[i].db, string);
+	}
+	/* no ready connections. just use the first one (we're guaranteed
+	   to always have one) */
+	return sql_escape_string(conns[0].db, string);
+}
+
+static void driver_sqlpool_timeout(struct sqlpool_db *db)
+{
+	int duration;
+
+	while (db->requests_head != NULL) {
+		struct sqlpool_request *request = db->requests_head;
+
+		if (request->created + SQL_QUERY_TIMEOUT_SECS > ioloop_time)
+			break;
+
+
+		if (request->query != NULL) {
+			e_error(sql_query_finished_event(&db->api, request->event,
+							 request->query, FALSE,
+							 &duration)->
+					add_str("error", "Query timed out")->
+					event(),
+				SQL_QUERY_FINISHED_FMT": Query timed out "
+	                        "(no free connections for %u secs)",
+				request->query, duration,
+				(unsigned int)(ioloop_time - request->created));
+		} else {
+			e_error(event_create_passthrough(request->event)->
+					add_str("error", "Timed out")->
+					set_name(SQL_TRANSACTION_FINISHED)->event(),
+				"Transaction timed out "
+				"(no free connections for %u secs)",
+				(unsigned int)(ioloop_time - request->created));
+		}
+		sqlpool_request_abort(&request);
+	}
+
+	if (db->requests_head == NULL)
+		timeout_remove(&db->request_to);
+}
+
+static void
+driver_sqlpool_prepend_request(struct sqlpool_db *db,
+			       struct sqlpool_request *request)
+{
+	DLLIST2_PREPEND(&db->requests_head, &db->requests_tail, request);
+	if (db->request_to == NULL) {
+		db->request_to = timeout_add(SQL_QUERY_TIMEOUT_SECS * 1000,
+					     driver_sqlpool_timeout, db);
+	}
+}
+
+static void
+driver_sqlpool_append_request(struct sqlpool_db *db,
+			      struct sqlpool_request *request)
+{
+	DLLIST2_APPEND(&db->requests_head, &db->requests_tail, request);
+	if (db->request_to == NULL) {
+		db->request_to = timeout_add(SQL_QUERY_TIMEOUT_SECS * 1000,
+					     driver_sqlpool_timeout, db);
+	}
+}
+
+static void
+driver_sqlpool_query_callback(struct sql_result *result,
+			      struct sqlpool_request *request)
+{
+	struct sqlpool_db *db = request->db;
+	const struct sqlpool_connection *conn = NULL;
+	struct sql_db *conndb;
+
+	if (result->failed_try_retry &&
+	    request->retry_count < array_count(&db->hosts)) {
+		e_warning(db->api.event, "Query failed, retrying: %s",
+			  sql_result_get_error(result));
+		request->retry_count++;
+		driver_sqlpool_prepend_request(db, request);
+
+		if (driver_sqlpool_get_connection(request->db,
+						  request->host_idx, &conn)) {
+			request->host_idx = conn->host_idx;
+			sqlpool_request_send_next(db, conn->db);
+		}
+	} else {
+		if (result->failed) {
+			e_error(db->api.event, "Query failed, aborting: %s",
+				request->query);
+		}
+		conndb = result->db;
+
+		if (request->callback != NULL)
+			request->callback(result, request->context);
+		sqlpool_request_free(&request);
+
+		sqlpool_request_send_next(db, conndb);
+	}
+}
+
+static void ATTR_NULL(3, 4)
+driver_sqlpool_query(struct sql_db *_db, const char *query,
+		     sql_query_callback_t *callback, void *context)
+{
+        struct sqlpool_db *db = (struct sqlpool_db *)_db;
+	struct sqlpool_request *request;
+	const struct sqlpool_connection *conn;
+
+	request = sqlpool_request_new(db, query);
+	request->callback = callback;
+	request->context = context;
+
+	if (!driver_sqlpool_get_connection(db, UINT_MAX, &conn))
+		driver_sqlpool_append_request(db, request);
+	else {
+		request->host_idx = conn->host_idx;
+		sql_query(conn->db, query, driver_sqlpool_query_callback,
+			  request);
+	}
+}
+
+static void driver_sqlpool_exec(struct sql_db *_db, const char *query)
+{
+	driver_sqlpool_query(_db, query, NULL, NULL);
+}
+
+static struct sql_result *
+driver_sqlpool_query_s(struct sql_db *_db, const char *query)
+{
+        struct sqlpool_db *db = (struct sqlpool_db *)_db;
+	const struct sqlpool_connection *conn;
+	struct sql_result *result;
+
+	if (!driver_sqlpool_get_sync_connection(db, &conn)) {
+		sql_not_connected_result.refcount++;
+		return &sql_not_connected_result;
+	}
+
+	result = sql_query_s(conn->db, query);
+	if (result->failed_try_retry) {
+		if (!driver_sqlpool_get_sync_connection(db, &conn))
+			return result;
+
+		sql_result_unref(result);
+		result = sql_query_s(conn->db, query);
+	}
+	return result;
+}
+
+static struct sql_transaction_context *
+driver_sqlpool_transaction_begin(struct sql_db *_db)
+{
+	struct sqlpool_transaction_context *ctx;
+
+	ctx = i_new(struct sqlpool_transaction_context, 1);
+	ctx->ctx.db = _db;
+
+	/* queue changes until commit. even if we did have a free connection
+	   now, don't use it or multiple open transactions could tie up all
+	   connections. */
+	ctx->query_pool = pool_alloconly_create("sqlpool transaction", 1024);
+	return &ctx->ctx;
+}
+
+static void
+driver_sqlpool_transaction_free(struct sqlpool_transaction_context *ctx)
+{
+	if (ctx->commit_request != NULL)
+		sqlpool_request_abort(&ctx->commit_request);
+	pool_unref(&ctx->query_pool);
+	i_free(ctx);
+}
+
+static void
+driver_sqlpool_commit_callback(const struct sql_commit_result *result,
+			       struct sqlpool_transaction_context *ctx)
+{
+	ctx->callback(result, ctx->context);
+	driver_sqlpool_transaction_free(ctx);
+}
+
+static void
+driver_sqlpool_transaction_commit(struct sql_transaction_context *_ctx,
+				  sql_commit_callback_t *callback,
+				  void *context)
+{
+	struct sqlpool_transaction_context *ctx =
+		(struct sqlpool_transaction_context *)_ctx;
+	struct sqlpool_db *db = (struct sqlpool_db *)_ctx->db;
+	const struct sqlpool_connection *conn;
+
+	ctx->callback = callback;
+	ctx->context = context;
+
+	ctx->commit_request = sqlpool_request_new(db, NULL);
+	ctx->commit_request->trans = ctx;
+
+	if (driver_sqlpool_get_connection(db, UINT_MAX, &conn))
+		sqlpool_request_handle_transaction(conn->db, ctx);
+	else
+		driver_sqlpool_append_request(db, ctx->commit_request);
+}
+
+static int
+driver_sqlpool_transaction_commit_s(struct sql_transaction_context *_ctx,
+				    const char **error_r)
+{
+	struct sqlpool_transaction_context *ctx =
+		(struct sqlpool_transaction_context *)_ctx;
+        struct sqlpool_db *db = (struct sqlpool_db *)_ctx->db;
+	const struct sqlpool_connection *conn;
+	struct sql_transaction_context *conn_trans;
+	int ret;
+
+	*error_r = NULL;
+
+	if (!driver_sqlpool_get_sync_connection(db, &conn)) {
+		*error_r = SQL_ERRSTR_NOT_CONNECTED;
+		driver_sqlpool_transaction_free(ctx);
+		return -1;
+	}
+
+	conn_trans = driver_sqlpool_new_conn_trans(ctx, conn->db);
+	ret = sql_transaction_commit_s(&conn_trans, error_r);
+	driver_sqlpool_transaction_free(ctx);
+	return ret;
+}
+
+static void
+driver_sqlpool_transaction_rollback(struct sql_transaction_context *_ctx)
+{
+	struct sqlpool_transaction_context *ctx =
+		(struct sqlpool_transaction_context *)_ctx;
+
+	driver_sqlpool_transaction_free(ctx);
+}
+
+static void
+driver_sqlpool_update(struct sql_transaction_context *_ctx, const char *query,
+		      unsigned int *affected_rows)
+{
+	struct sqlpool_transaction_context *ctx =
+		(struct sqlpool_transaction_context *)_ctx;
+
+	/* we didn't get a connection for transaction immediately.
+	   queue updates until commit transfers all of these */
+	sql_transaction_add_query(&ctx->ctx, ctx->query_pool,
+				  query, affected_rows);
+}
+
+static const char *
+driver_sqlpool_escape_blob(struct sql_db *_db,
+			   const unsigned char *data, size_t size)
+{
+	struct sqlpool_db *db = (struct sqlpool_db *)_db;
+	const struct sqlpool_connection *conns;
+	unsigned int i, count;
+
+	/* use the first ready connection */
+	conns = array_get(&db->all_connections, &count);
+	for (i = 0; i < count; i++) {
+		if (SQL_DB_IS_READY(conns[i].db))
+			return sql_escape_blob(conns[i].db, data, size);
+	}
+	/* no ready connections. just use the first one (we're guaranteed
+	   to always have one) */
+	return sql_escape_blob(conns[0].db, data, size);
+}
+
+static void driver_sqlpool_wait(struct sql_db *_db)
+{
+	struct sqlpool_db *db = (struct sqlpool_db *)_db;
+	const struct sqlpool_connection *conn;
+
+	array_foreach(&db->all_connections, conn)
+		sql_wait(conn->db);
+}
+
+struct sql_db driver_sqlpool_db = {
+	"",
+
+	.v = {
+		.get_flags = driver_sqlpool_get_flags,
+		.deinit = driver_sqlpool_deinit,
+		.connect = driver_sqlpool_connect,
+		.disconnect = driver_sqlpool_disconnect,
+		.escape_string = driver_sqlpool_escape_string,
+		.exec = driver_sqlpool_exec,
+		.query = driver_sqlpool_query,
+		.query_s = driver_sqlpool_query_s,
+		.wait = driver_sqlpool_wait,
+
+		.transaction_begin = driver_sqlpool_transaction_begin,
+		.transaction_commit = driver_sqlpool_transaction_commit,
+		.transaction_commit_s = driver_sqlpool_transaction_commit_s,
+		.transaction_rollback = driver_sqlpool_transaction_rollback,
+
+		.update = driver_sqlpool_update,
+
+		.escape_blob = driver_sqlpool_escape_blob,
+	}
+};
diff --git a/src/lib-sql/driver-test.c b/src/lib-sql/driver-test.c
new file mode 100644
index 0000000..9d4db76
--- /dev/null
+++ b/src/lib-sql/driver-test.c
@@ -0,0 +1,514 @@
+/* Copyright (c) 2017-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "test-lib.h"
+#include "str.h"
+#include "buffer.h"
+#include "sql-api-private.h"
+#include "driver-test.h"
+#include "array.h"
+#include "hex-binary.h"
+
+struct test_sql_db {
+	struct sql_db api;
+
+	pool_t pool;
+	ARRAY(struct test_driver_result) expected;
+	const char *error;
+	bool failed:1;
+};
+
+struct test_sql_result {
+	struct sql_result api;
+	struct test_driver_result *result;
+	const char *error;
+};
+
+static struct sql_db *driver_test_mysql_init(const char *connect_string);
+static struct sql_db *driver_test_cassandra_init(const char *connect_string);
+static struct sql_db *driver_test_sqlite_init(const char *connect_string);
+static void driver_test_deinit(struct sql_db *_db);
+static int driver_test_connect(struct sql_db *_db);
+static void driver_test_disconnect(struct sql_db *_db);
+static const char *
+driver_test_mysql_escape_string(struct sql_db *_db, const char *string);
+static const char *
+driver_test_escape_string(struct sql_db *_db, const char *string);
+static void driver_test_exec(struct sql_db *_db, const char *query);
+static void driver_test_query(struct sql_db *_db, const char *query,
+			       sql_query_callback_t *callback, void *context);
+static struct sql_result *
+driver_test_query_s(struct sql_db *_db, const char *query);
+static struct sql_transaction_context *
+driver_test_transaction_begin(struct sql_db *_db);
+static void driver_test_transaction_commit(struct sql_transaction_context *ctx,
+					    sql_commit_callback_t *callback,
+					    void *context);
+static int
+driver_test_transaction_commit_s(struct sql_transaction_context *ctx,
+				  const char **error_r);
+static void
+driver_test_transaction_rollback(struct sql_transaction_context *ctx);
+static void
+driver_test_update(struct sql_transaction_context *ctx, const char *query,
+		    unsigned int *affected_rows);
+static const char *
+driver_test_mysql_escape_blob(struct sql_db *_db, const unsigned char *data,
+			 size_t size);
+static const char *
+driver_test_escape_blob(struct sql_db *_db, const unsigned char *data,
+			 size_t size);
+
+static void driver_test_result_free(struct sql_result *result);
+static int driver_test_result_next_row(struct sql_result *result);
+
+static unsigned int
+driver_test_result_get_fields_count(struct sql_result *result);
+static const char *
+driver_test_result_get_field_name(struct sql_result *result, unsigned int idx);
+static int
+driver_test_result_find_field(struct sql_result *result, const char *field_name);
+
+static const char *
+driver_test_result_get_field_value(struct sql_result *result, unsigned int idx);
+static const unsigned char *
+driver_test_result_get_field_value_binary(struct sql_result *result,
+					   unsigned int idx, size_t *size_r);
+static const char *
+driver_test_result_find_field_value(struct sql_result *result,
+				     const char *field_name);
+static const char *const *
+driver_test_result_get_values(struct sql_result *result);
+
+const char *driver_test_result_get_error(struct sql_result *result);
+
+
+const struct sql_db driver_test_mysql_db = {
+	.name = "mysql",
+	.flags = SQL_DB_FLAG_BLOCKING | SQL_DB_FLAG_ON_DUPLICATE_KEY,
+
+	.v = {
+		.init = driver_test_mysql_init,
+		.deinit = driver_test_deinit,
+		.connect = driver_test_connect,
+		.disconnect = driver_test_disconnect,
+		.escape_string = driver_test_mysql_escape_string,
+		.exec = driver_test_exec,
+		.query = driver_test_query,
+		.query_s = driver_test_query_s,
+
+		.transaction_begin = driver_test_transaction_begin,
+		.transaction_commit = driver_test_transaction_commit,
+		.transaction_commit_s = driver_test_transaction_commit_s,
+		.transaction_rollback = driver_test_transaction_rollback,
+		.update = driver_test_update,
+
+		.escape_blob = driver_test_mysql_escape_blob,
+	}
+};
+
+const struct sql_db driver_test_cassandra_db = {
+	.name = "cassandra",
+
+	.v = {
+		.init = driver_test_cassandra_init,
+		.deinit = driver_test_deinit,
+		.connect = driver_test_connect,
+		.disconnect = driver_test_disconnect,
+		.escape_string = driver_test_escape_string,
+		.exec = driver_test_exec,
+		.query = driver_test_query,
+		.query_s = driver_test_query_s,
+
+		.transaction_begin = driver_test_transaction_begin,
+		.transaction_commit = driver_test_transaction_commit,
+		.transaction_commit_s = driver_test_transaction_commit_s,
+		.transaction_rollback = driver_test_transaction_rollback,
+		.update = driver_test_update,
+
+		.escape_blob = driver_test_escape_blob,
+	}
+};
+
+const struct sql_db driver_test_sqlite_db = {
+	.name = "sqlite",
+	.flags = SQL_DB_FLAG_ON_CONFLICT_DO | SQL_DB_FLAG_BLOCKING,
+
+	.v = {
+		.init = driver_test_sqlite_init,
+		.deinit = driver_test_deinit,
+		.connect = driver_test_connect,
+		.disconnect = driver_test_disconnect,
+		.escape_string = driver_test_escape_string,
+		.exec = driver_test_exec,
+		.query = driver_test_query,
+		.query_s = driver_test_query_s,
+
+		.transaction_begin = driver_test_transaction_begin,
+		.transaction_commit = driver_test_transaction_commit,
+		.transaction_commit_s = driver_test_transaction_commit_s,
+		.transaction_rollback = driver_test_transaction_rollback,
+		.update = driver_test_update,
+
+		.escape_blob = driver_test_escape_blob,
+	}
+};
+
+
+const struct sql_result driver_test_result = {
+	.v = {
+		.free = driver_test_result_free,
+		.next_row = driver_test_result_next_row,
+		.get_fields_count = driver_test_result_get_fields_count,
+		.get_field_name = driver_test_result_get_field_name,
+		.find_field = driver_test_result_find_field,
+		.get_field_value = driver_test_result_get_field_value,
+		.get_field_value_binary = driver_test_result_get_field_value_binary,
+		.find_field_value = driver_test_result_find_field_value,
+		.get_values = driver_test_result_get_values,
+		.get_error = driver_test_result_get_error,
+	}
+};
+
+void sql_driver_test_register(void)
+{
+	sql_driver_register(&driver_test_mysql_db);
+	sql_driver_register(&driver_test_cassandra_db);
+	sql_driver_register(&driver_test_sqlite_db);
+}
+
+void sql_driver_test_unregister(void)
+{
+	sql_driver_unregister(&driver_test_mysql_db);
+	sql_driver_unregister(&driver_test_cassandra_db);
+	sql_driver_unregister(&driver_test_sqlite_db);
+}
+
+static struct sql_db *driver_test_init(const struct sql_db *driver,
+					const char *connect_string ATTR_UNUSED)
+{
+	pool_t pool = pool_alloconly_create(MEMPOOL_GROWING" test sql driver", 2048);
+	struct test_sql_db *ret = p_new(pool, struct test_sql_db, 1);
+	ret->pool = pool;
+	ret->api = *driver;
+	p_array_init(&ret->expected, pool, 8);
+	return &ret->api;
+}
+
+static struct sql_db *driver_test_mysql_init(const char *connect_string)
+{
+	return driver_test_init(&driver_test_mysql_db, connect_string);
+}
+
+static struct sql_db *driver_test_cassandra_init(const char *connect_string)
+{
+	return driver_test_init(&driver_test_cassandra_db, connect_string);
+}
+
+static struct sql_db *driver_test_sqlite_init(const char *connect_string)
+{
+	return driver_test_init(&driver_test_sqlite_db, connect_string);
+}
+
+static void driver_test_deinit(struct sql_db *_db ATTR_UNUSED)
+{
+	struct test_sql_db *db = (struct test_sql_db*)_db;
+	array_free(&_db->module_contexts);
+	pool_unref(&db->pool);
+}
+
+static int driver_test_connect(struct sql_db *_db ATTR_UNUSED)
+{
+	/* nix */
+	return 0;
+}
+
+static void driver_test_disconnect(struct sql_db *_db ATTR_UNUSED)
+{ }
+
+static const char *
+driver_test_mysql_escape_string(struct sql_db *_db ATTR_UNUSED,
+				 const char *string)
+{
+	string_t *esc = t_str_new(strlen(string));
+	for(const char *ptr = string; *ptr != '\0'; ptr++) {
+		if (*ptr == '\n' || *ptr == '\r' || *ptr == '\\' ||
+		    *ptr == '\'' || *ptr == '\"' || *ptr == '\x1a')
+			str_append_c(esc, '\\');
+		str_append_c(esc, *ptr);
+	}
+	return str_c(esc);
+}
+
+static const char *
+driver_test_escape_string(struct sql_db *_db ATTR_UNUSED, const char *string)
+{
+	return string;
+}
+
+static void driver_test_exec(struct sql_db *_db, const char *query)
+{
+	struct test_sql_db *db = (struct test_sql_db*)_db;
+	struct test_driver_result *result =
+		array_front_modifiable(&db->expected);
+	i_assert(result->cur < result->nqueries);
+
+/*	i_debug("DUMMY EXECUTE: %s", query);
+	i_debug("DUMMY EXPECT : %s", result->queries[result->cur]); */
+
+	test_assert_strcmp(result->queries[result->cur], query);
+
+	if (strcmp(result->queries[result->cur], query) != 0) {
+		db->error = "Invalid query";
+		db->failed = TRUE;
+	}
+
+	result->cur++;
+}
+
+static void
+driver_test_query(struct sql_db *_db, const char *query,
+		   sql_query_callback_t *callback, void *context)
+{
+	struct sql_result *result = driver_test_query_s(_db, query);
+	if (callback != NULL)
+		callback(result, context);
+}
+
+static struct sql_result *
+driver_test_query_s(struct sql_db *_db, const char *query)
+{
+	struct test_sql_db *db = (struct test_sql_db*)_db;
+	struct test_driver_result *result =
+		array_front_modifiable(&db->expected);
+	struct test_sql_result *res = i_new(struct test_sql_result, 1);
+
+	driver_test_exec(_db, query);
+
+	if (db->failed) {
+		res->api.failed = TRUE;
+	}
+
+	res->api.v = driver_test_result.v;
+	res->api.db = _db;
+	if (result->result != NULL) {
+		res->result = i_new(struct test_driver_result, 1);
+		memcpy(res->result, result, sizeof(*result));
+	}
+	res->api.refcount = 1;
+
+	/* drop it from array if it's used up */
+	if (result->cur == result->nqueries)
+		array_pop_front(&db->expected);
+
+	return &res->api;
+}
+
+static struct sql_transaction_context *
+driver_test_transaction_begin(struct sql_db *_db)
+{
+	struct sql_transaction_context *ctx =
+		i_new(struct sql_transaction_context, 1);
+	ctx->db = _db;
+	return ctx;
+}
+
+static void
+driver_test_transaction_commit(struct sql_transaction_context *ctx,
+				sql_commit_callback_t *callback, void *context)
+{
+	struct sql_commit_result res;
+	res.error_type = driver_test_transaction_commit_s(ctx, &res.error);
+	callback(&res, context);
+}
+
+static int
+driver_test_transaction_commit_s(struct sql_transaction_context *ctx,
+				  const char **error_r)
+{
+	struct test_sql_db *db = (struct test_sql_db*)ctx->db;
+	int ret = 0;
+
+	if (db->error != NULL) {
+		*error_r = db->error;
+		ret = -1;
+	}
+	i_free(ctx);
+	db->error = NULL;
+	db->failed = FALSE;
+
+	return ret;
+}
+
+static void
+driver_test_transaction_rollback(struct sql_transaction_context *ctx)
+{
+	struct test_sql_db *db = (struct test_sql_db*)ctx->db;
+	i_free(ctx);
+	db->error = NULL;
+	db->failed = FALSE;
+}
+
+static void
+driver_test_update(struct sql_transaction_context *ctx, const char *query,
+		    unsigned int *affected_rows)
+{
+	struct test_sql_db *db= (struct test_sql_db*)ctx->db;
+	struct test_driver_result *result =
+		array_front_modifiable(&db->expected);
+	driver_test_exec(ctx->db, query);
+
+	if (affected_rows != NULL)
+		*affected_rows = result->affected_rows;
+
+	/* drop it from array if it's used up */
+	if (result->cur == result->nqueries)
+		array_pop_front(&db->expected);
+}
+
+static const char *
+driver_test_mysql_escape_blob(struct sql_db *_db ATTR_UNUSED,
+			       const unsigned char *data, size_t size)
+{
+	return t_strdup_printf("X'%s'", binary_to_hex(data,size));
+}
+
+static const char *
+driver_test_escape_blob(struct sql_db *_db ATTR_UNUSED,
+			 const unsigned char *data, size_t size)
+{
+	return t_strdup_printf("X'%s'", binary_to_hex(data,size));
+}
+
+static void driver_test_result_free(struct sql_result *result)
+{
+        struct test_sql_result *tsr =
+                (struct test_sql_result *)result;
+	if (tsr->result != NULL)
+		i_free(tsr->result);
+	i_free(result);
+}
+
+static int driver_test_result_next_row(struct sql_result *result)
+{
+	struct test_sql_result *tsr =
+		(struct test_sql_result *)result;
+	struct test_driver_result *r = tsr->result;
+
+	if (r == NULL) return 0;
+
+	struct test_driver_result_set *rs =
+		&(r->result[r->cur-1]);
+	if (rs->cur <= rs->rows) {
+		rs->cur++;
+	}
+
+	return rs->cur <= rs->rows ? 1 : 0;
+}
+
+static unsigned int
+driver_test_result_get_fields_count(struct sql_result *result)
+{
+        struct test_sql_result *tsr =
+                (struct test_sql_result *)result;
+        struct test_driver_result *r = tsr->result;
+	struct test_driver_result_set *rs =
+		&(r->result[r->cur-1]);
+	return rs->cols;
+}
+
+static const char *
+driver_test_result_get_field_name(struct sql_result *result, unsigned int idx)
+{
+        struct test_sql_result *tsr =
+                (struct test_sql_result *)result;
+        struct test_driver_result *r = tsr->result;
+	struct test_driver_result_set *rs =
+		&(r->result[r->cur-1]);
+	i_assert(idx < rs->cols);
+	return rs->col_names[idx];
+}
+
+static int
+driver_test_result_find_field(struct sql_result *result, const char *field_name)
+{
+        struct test_sql_result *tsr =
+                (struct test_sql_result *)result;
+        struct test_driver_result *r = tsr->result;
+	struct test_driver_result_set *rs =
+		&(r->result[r->cur-1]);
+	for(size_t i = 0; i < rs->cols; i++) {
+		if (strcmp(field_name, rs->col_names[i])==0)
+			return i;
+	}
+	return -1;
+}
+
+static const char *
+driver_test_result_get_field_value(struct sql_result *result, unsigned int idx)
+{
+        struct test_sql_result *tsr =
+                (struct test_sql_result *)result;
+        struct test_driver_result *r = tsr->result;
+	struct test_driver_result_set *rs =
+		&(r->result[r->cur-1]);
+
+	i_assert(idx < rs->cols);
+	i_assert(rs->cur <= rs->rows);
+
+	return rs->row_data[rs->cur-1][idx];
+}
+static const unsigned char *
+driver_test_result_get_field_value_binary(struct sql_result *result,
+					   unsigned int idx, size_t *size_r)
+{
+	buffer_t *buf = t_buffer_create(64);
+	const char *value = driver_test_result_get_field_value(result, idx);
+	/* expect it hex encoded */
+	if (hex_to_binary(value, buf) < 0) {
+		*size_r = 0;
+		return NULL;
+	}
+	*size_r = buf->used;
+	return buf->data;
+}
+static const char *
+driver_test_result_find_field_value(struct sql_result *result,
+				     const char *field_name)
+{
+	int idx = driver_test_result_find_field(result, field_name);
+	if (idx < 0) return NULL;
+	return driver_test_result_get_field_value(result, idx);
+}
+static const char *const *
+driver_test_result_get_values(struct sql_result *result)
+{
+        struct test_sql_result *tsr =
+                (struct test_sql_result *)result;
+        struct test_driver_result *r = tsr->result;
+	struct test_driver_result_set *rs =
+		&(r->result[r->cur-1]);
+	i_assert(rs->cur <= rs->rows);
+	return rs->row_data[rs->cur-1];
+}
+
+const char *driver_test_result_get_error(struct sql_result *result)
+{
+        struct test_sql_result *tsr =
+                (struct test_sql_result *)result;
+	return tsr->error;
+}
+
+
+void sql_driver_test_add_expected_result(struct sql_db *_db,
+					  const struct test_driver_result *result)
+{
+	struct test_sql_db *db = (struct test_sql_db*)_db;
+	array_push_back(&db->expected, result);
+}
+
+void sql_driver_test_clear_expected_results(struct sql_db *_db)
+{
+	struct test_sql_db *db = (struct test_sql_db*)_db;
+	array_clear(&db->expected);
+}
diff --git a/src/lib-sql/driver-test.h b/src/lib-sql/driver-test.h
new file mode 100644
index 0000000..49915ad
--- /dev/null
+++ b/src/lib-sql/driver-test.h
@@ -0,0 +1,28 @@
+#ifndef DRIVER_TEST_H
+#define DRIVER_TEST_H 1
+
+struct test_driver_result_set {
+	size_t rows, cols, cur;
+	const char *const *col_names;
+	const char ***row_data;
+};
+
+struct test_driver_result {
+	/* expected queries */
+	size_t nqueries;
+	size_t cur;
+	unsigned int affected_rows;
+	const char *const *queries;
+
+	/* test result, rows and columns */
+	struct test_driver_result_set *result;
+};
+
+void sql_driver_test_register(void);
+void sql_driver_test_unregister(void);
+
+void sql_driver_test_add_expected_result(struct sql_db *_db,
+					 const struct test_driver_result *result);
+void sql_driver_test_clear_expected_results(struct sql_db *_db);
+
+#endif
diff --git a/src/lib-sql/sql-api-private.h b/src/lib-sql/sql-api-private.h
new file mode 100644
index 0000000..192afb6
--- /dev/null
+++ b/src/lib-sql/sql-api-private.h
@@ -0,0 +1,251 @@
+#ifndef SQL_API_PRIVATE_H
+#define SQL_API_PRIVATE_H
+
+#include "sql-api.h"
+#include "module-context.h"
+
+enum sql_db_state {
+	/* not connected to database */
+	SQL_DB_STATE_DISCONNECTED,
+	/* waiting for connection attempt to succeed or fail */
+	SQL_DB_STATE_CONNECTING,
+	/* connected, allowing more queries */
+	SQL_DB_STATE_IDLE,
+	/* connected, no more queries allowed */
+	SQL_DB_STATE_BUSY
+};
+
+/* Minimum delay between reconnecting to same server */
+#define SQL_CONNECT_MIN_DELAY 1
+/* Maximum time to avoiding reconnecting to same server */
+#define SQL_CONNECT_MAX_DELAY (60*30)
+/* If no servers are connected but a query is requested, try reconnecting to
+   next server which has been disconnected longer than this (with a single
+   server setup this is really the "max delay" and the SQL_CONNECT_MAX_DELAY
+   is never used). */
+#define SQL_CONNECT_RESET_DELAY 15
+/* Abort connect() if it can't connect within this time. */
+#define SQL_CONNECT_TIMEOUT_SECS 5
+/* Abort queries after this many seconds */
+#define SQL_QUERY_TIMEOUT_SECS 60
+/* Default max. number of connections to create per host */
+#define SQL_DEFAULT_CONNECTION_LIMIT 5
+
+#define SQL_DB_IS_READY(db) \
+	((db)->state == SQL_DB_STATE_IDLE)
+#define SQL_ERRSTR_NOT_CONNECTED "Not connected to database"
+
+/* What is considered slow query */
+#define SQL_SLOW_QUERY_MSEC 1000
+
+#define SQL_QUERY_FINISHED "sql_query_finished"
+#define SQL_CONNECTION_FINISHED "sql_connection_finished"
+#define SQL_TRANSACTION_FINISHED "sql_transaction_finished"
+
+#define SQL_QUERY_FINISHED_FMT "Finished query '%s' in %u msecs"
+
+struct sql_db_module_register {
+	unsigned int id;
+};
+
+union sql_db_module_context {
+	struct sql_db_module_register *reg;
+};
+
+extern struct sql_db_module_register sql_db_module_register;
+
+extern struct event_category event_category_sql;
+
+struct sql_transaction_query {
+	struct sql_transaction_query *next;
+	struct sql_transaction_context *trans;
+
+	const char *query;
+	unsigned int *affected_rows;
+};
+
+struct sql_db_vfuncs {
+	struct sql_db *(*init)(const char *connect_string);
+	int (*init_full)(const struct sql_settings *set, struct sql_db **db_r,
+			 const char **error);
+	void (*deinit)(struct sql_db *db);
+	void (*unref)(struct sql_db *db);
+	void (*wait) (struct sql_db *db);
+
+	enum sql_db_flags (*get_flags)(struct sql_db *db);
+
+	int (*connect)(struct sql_db *db);
+	void (*disconnect)(struct sql_db *db);
+	const char *(*escape_string)(struct sql_db *db, const char *string);
+
+	void (*exec)(struct sql_db *db, const char *query);
+	void (*query)(struct sql_db *db, const char *query,
+		      sql_query_callback_t *callback, void *context);
+	struct sql_result *(*query_s)(struct sql_db *db, const char *query);
+
+	struct sql_transaction_context *(*transaction_begin)(struct sql_db *db);
+	void (*transaction_commit)(struct sql_transaction_context *ctx,
+				   sql_commit_callback_t *callback,
+				   void *context);
+	int (*transaction_commit_s)(struct sql_transaction_context *ctx,
+				    const char **error_r);
+	void (*transaction_rollback)(struct sql_transaction_context *ctx);
+
+	void (*update)(struct sql_transaction_context *ctx, const char *query,
+		       unsigned int *affected_rows);
+	const char *(*escape_blob)(struct sql_db *db,
+				   const unsigned char *data, size_t size);
+
+	struct sql_prepared_statement *
+		(*prepared_statement_init)(struct sql_db *db,
+					   const char *query_template);
+	void (*prepared_statement_deinit)(struct sql_prepared_statement *prep_stmt);
+
+
+	struct sql_statement *
+		(*statement_init)(struct sql_db *db, const char *query_template);
+	struct sql_statement *
+		(*statement_init_prepared)(struct sql_prepared_statement *prep_stmt);
+	void (*statement_abort)(struct sql_statement *stmt);
+	void (*statement_set_timestamp)(struct sql_statement *stmt,
+					const struct timespec *ts);
+	void (*statement_bind_str)(struct sql_statement *stmt,
+				   unsigned int column_idx, const char *value);
+	void (*statement_bind_binary)(struct sql_statement *stmt,
+				      unsigned int column_idx, const void *value,
+				      size_t value_size);
+	void (*statement_bind_int64)(struct sql_statement *stmt,
+				     unsigned int column_idx, int64_t value);
+	void (*statement_query)(struct sql_statement *stmt,
+				sql_query_callback_t *callback, void *context);
+	struct sql_result *(*statement_query_s)(struct sql_statement *stmt);
+	void (*update_stmt)(struct sql_transaction_context *ctx,
+			    struct sql_statement *stmt,
+			    unsigned int *affected_rows);
+};
+
+struct sql_db {
+	const char *name;
+	enum sql_db_flags flags;
+	int refcount;
+
+	struct sql_db_vfuncs v;
+	ARRAY(union sql_db_module_context *) module_contexts;
+
+	void (*state_change_callback)(struct sql_db *db,
+				      enum sql_db_state prev_state,
+				      void *context);
+	void *state_change_context;
+
+	struct event *event;
+	HASH_TABLE(char *, struct sql_prepared_statement *) prepared_stmt_hash;
+
+	enum sql_db_state state;
+	/* last time we started connecting to this server
+	   (which may or may not have succeeded) */
+	time_t last_connect_try;
+	unsigned int connect_delay;
+	unsigned int connect_failure_count;
+	struct timeout *to_reconnect;
+
+	uint64_t succeeded_queries;
+	uint64_t failed_queries;
+	/* includes both succeeded and failed */
+	uint64_t slow_queries;
+
+	bool no_reconnect:1;
+};
+
+struct sql_result_vfuncs {
+	void (*free)(struct sql_result *result);
+	int (*next_row)(struct sql_result *result);
+
+	unsigned int (*get_fields_count)(struct sql_result *result);
+	const char *(*get_field_name)(struct sql_result *result,
+				      unsigned int idx);
+	int (*find_field)(struct sql_result *result, const char *field_name);
+
+	const char *(*get_field_value)(struct sql_result *result,
+				       unsigned int idx);
+	const unsigned char *
+		(*get_field_value_binary)(struct sql_result *result,
+					  unsigned int idx,
+					  size_t *size_r);
+	const char *(*find_field_value)(struct sql_result *result,
+					const char *field_name);
+	const char *const *(*get_values)(struct sql_result *result);
+
+	const char *(*get_error)(struct sql_result *result);
+	void (*more)(struct sql_result **result, bool async,
+		     sql_query_callback_t *callback, void *context);
+};
+
+struct sql_prepared_statement {
+	struct sql_db *db;
+	int refcount;
+	char *query_template;
+};
+
+struct sql_statement {
+	struct sql_db *db;
+
+	pool_t pool;
+	const char *query_template;
+	ARRAY_TYPE(const_string) args;
+};
+
+struct sql_field_map {
+	enum sql_field_type type;
+	size_t offset;
+};
+
+struct sql_result {
+	struct sql_result_vfuncs v;
+	int refcount;
+
+	struct sql_db *db;
+	const struct sql_field_def *fields;
+
+	unsigned int map_size;
+	struct sql_field_map *map;
+	void *fetch_dest;
+	struct event *event;
+	size_t fetch_dest_size;
+	enum sql_result_error_type error_type;
+
+	bool failed:1;
+	bool failed_try_retry:1;
+	bool callback:1;
+};
+
+struct sql_transaction_context {
+	struct sql_db *db;
+	struct event *event;
+
+	/* commit() must use this query list if head is non-NULL. */
+	struct sql_transaction_query *head, *tail;
+};
+
+ARRAY_DEFINE_TYPE(sql_drivers, const struct sql_db *);
+
+extern ARRAY_TYPE(sql_drivers) sql_drivers;
+extern struct sql_result sql_not_connected_result;
+
+void sql_init_common(struct sql_db *db);
+struct sql_db *
+driver_sqlpool_init(const char *connect_string, const struct sql_db *driver);
+int driver_sqlpool_init_full(const struct sql_settings *set, const struct sql_db *driver,
+			     struct sql_db **db_r, const char **error_r);
+
+void sql_db_set_state(struct sql_db *db, enum sql_db_state state);
+
+void sql_transaction_add_query(struct sql_transaction_context *ctx, pool_t pool,
+			       const char *query, unsigned int *affected_rows);
+const char *sql_statement_get_query(struct sql_statement *stmt);
+
+void sql_connection_log_finished(struct sql_db *db);
+struct event_passthrough *
+sql_query_finished_event(struct sql_db *db, struct event *event, const char *query,
+			 bool success, int *duration_r);
+struct event_passthrough *sql_transaction_finished_event(struct sql_transaction_context *ctx);
+#endif
diff --git a/src/lib-sql/sql-api.c b/src/lib-sql/sql-api.c
new file mode 100644
index 0000000..919513b
--- /dev/null
+++ b/src/lib-sql/sql-api.c
@@ -0,0 +1,833 @@
+/* Copyright (c) 2004-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "array.h"
+#include "ioloop.h"
+#include "hash.h"
+#include "str.h"
+#include "time-util.h"
+#include "sql-api-private.h"
+
+#include <time.h>
+
+struct event_category event_category_sql = {
+	.name = "sql",
+};
+
+struct sql_db_module_register sql_db_module_register = { 0 };
+ARRAY_TYPE(sql_drivers) sql_drivers;
+
+void sql_drivers_init(void)
+{
+	i_array_init(&sql_drivers, 8);
+}
+
+void sql_drivers_deinit(void)
+{
+	array_free(&sql_drivers);
+}
+
+static const struct sql_db *sql_driver_lookup(const char *name)
+{
+	const struct sql_db *const *drivers;
+	unsigned int i, count;
+
+	drivers = array_get(&sql_drivers, &count);
+	for (i = 0; i < count; i++) {
+		if (strcmp(drivers[i]->name, name) == 0)
+			return drivers[i];
+	}
+	return NULL;
+}
+
+void sql_driver_register(const struct sql_db *driver)
+{
+	if (sql_driver_lookup(driver->name) != NULL) {
+		i_fatal("sql_driver_register(%s): Already registered",
+			driver->name);
+	}
+	array_push_back(&sql_drivers, &driver);
+}
+
+void sql_driver_unregister(const struct sql_db *driver)
+{
+	const struct sql_db *const *drivers;
+	unsigned int i, count;
+
+	drivers = array_get(&sql_drivers, &count);
+	for (i = 0; i < count; i++) {
+		if (drivers[i] == driver) {
+			array_delete(&sql_drivers, i, 1);
+			break;
+		}
+	}
+}
+
+struct sql_db *sql_init(const char *db_driver, const char *connect_string)
+{
+	const char *error;
+	struct sql_db *db;
+	struct sql_settings set = {
+		.driver = db_driver,
+		.connect_string = connect_string,
+	};
+
+	if (sql_init_full(&set, &db, &error) < 0)
+		i_fatal("%s", error);
+	return db;
+}
+
+int sql_init_full(const struct sql_settings *set, struct sql_db **db_r,
+		  const char **error_r)
+{
+	const struct sql_db *driver;
+	struct sql_db *db;
+	int ret = 0;
+
+	i_assert(set->connect_string != NULL);
+
+	driver = sql_driver_lookup(set->driver);
+	if (driver == NULL) {
+		*error_r = t_strdup_printf("Unknown database driver '%s'", set->driver);
+		return -1;
+	}
+
+	if ((driver->flags & SQL_DB_FLAG_POOLED) == 0) {
+		if (driver->v.init_full == NULL) {
+			db = driver->v.init(set->connect_string);
+		} else
+			ret = driver->v.init_full(set, &db, error_r);
+	} else
+		ret = driver_sqlpool_init_full(set, driver, &db, error_r);
+
+	if (ret < 0)
+		return -1;
+
+	sql_init_common(db);
+	*db_r = db;
+	return 0;
+}
+
+void sql_init_common(struct sql_db *db)
+{
+	db->refcount = 1;
+	i_array_init(&db->module_contexts, 5);
+	hash_table_create(&db->prepared_stmt_hash, default_pool, 0,
+			  str_hash, strcmp);
+}
+
+void sql_ref(struct sql_db *db)
+{
+	i_assert(db->refcount > 0);
+	db->refcount++;
+}
+
+static void
+default_sql_prepared_statement_deinit(struct sql_prepared_statement *prep_stmt)
+{
+	i_free(prep_stmt->query_template);
+	i_free(prep_stmt);
+}
+
+static void sql_prepared_statements_free(struct sql_db *db)
+{
+	struct hash_iterate_context *iter;
+	struct sql_prepared_statement *prep_stmt;
+	char *query;
+
+	iter = hash_table_iterate_init(db->prepared_stmt_hash);
+	while (hash_table_iterate(iter, db->prepared_stmt_hash, &query, &prep_stmt)) {
+		i_assert(prep_stmt->refcount == 0);
+		if (prep_stmt->db->v.prepared_statement_deinit != NULL)
+			prep_stmt->db->v.prepared_statement_deinit(prep_stmt);
+		else
+			default_sql_prepared_statement_deinit(prep_stmt);
+	}
+	hash_table_iterate_deinit(&iter);
+	hash_table_clear(db->prepared_stmt_hash, TRUE);
+}
+
+void sql_unref(struct sql_db **_db)
+{
+	struct sql_db *db = *_db;
+
+	*_db = NULL;
+
+	i_assert(db->refcount > 0);
+	if (db->v.unref != NULL)
+		db->v.unref(db);
+	if (--db->refcount > 0)
+		return;
+
+	timeout_remove(&db->to_reconnect);
+	sql_prepared_statements_free(db);
+	hash_table_destroy(&db->prepared_stmt_hash);
+	db->v.deinit(db);
+}
+
+enum sql_db_flags sql_get_flags(struct sql_db *db)
+{
+	if (db->v.get_flags != NULL)
+		return db->v.get_flags(db);
+	else
+		return db->flags;
+}
+
+int sql_connect(struct sql_db *db)
+{
+	time_t now;
+
+	switch (db->state) {
+	case SQL_DB_STATE_DISCONNECTED:
+		break;
+	case SQL_DB_STATE_CONNECTING:
+		return 0;
+	default:
+		return 1;
+	}
+
+	/* don't try reconnecting more than once a second */
+	now = time(NULL);
+	if (db->last_connect_try + (time_t)db->connect_delay > now)
+		return -1;
+	db->last_connect_try = now;
+
+	return db->v.connect(db);
+}
+
+void sql_disconnect(struct sql_db *db)
+{
+	timeout_remove(&db->to_reconnect);
+	db->v.disconnect(db);
+}
+
+const char *sql_escape_string(struct sql_db *db, const char *string)
+{
+	return db->v.escape_string(db, string);
+}
+
+const char *sql_escape_blob(struct sql_db *db,
+			    const unsigned char *data, size_t size)
+{
+	return db->v.escape_blob(db, data, size);
+}
+
+void sql_exec(struct sql_db *db, const char *query)
+{
+	db->v.exec(db, query);
+}
+
+#undef sql_query
+void sql_query(struct sql_db *db, const char *query,
+	       sql_query_callback_t *callback, void *context)
+{
+	db->v.query(db, query, callback, context);
+}
+
+struct sql_result *sql_query_s(struct sql_db *db, const char *query)
+{
+	return db->v.query_s(db, query);
+}
+
+static struct sql_prepared_statement *
+default_sql_prepared_statement_init(struct sql_db *db,
+				    const char *query_template)
+{
+	struct sql_prepared_statement *prep_stmt;
+
+	prep_stmt = i_new(struct sql_prepared_statement, 1);
+	prep_stmt->db = db;
+	prep_stmt->refcount = 1;
+	prep_stmt->query_template = i_strdup(query_template);
+	return prep_stmt;
+}
+
+static struct sql_statement *
+default_sql_statement_init_prepared(struct sql_prepared_statement *stmt)
+{
+	return sql_statement_init(stmt->db, stmt->query_template);
+}
+
+const char *sql_statement_get_query(struct sql_statement *stmt)
+{
+	string_t *query = t_str_new(128);
+	const char *const *args;
+	unsigned int i, args_count, arg_pos = 0;
+
+	args = array_get(&stmt->args, &args_count);
+
+	for (i = 0; stmt->query_template[i] != '\0'; i++) {
+		if (stmt->query_template[i] == '?') {
+			if (arg_pos >= args_count ||
+			    args[arg_pos] == NULL) {
+				i_panic("lib-sql: Missing bind for arg #%u in statement: %s",
+					arg_pos, stmt->query_template);
+			}
+			str_append(query, args[arg_pos++]);
+		} else {
+			str_append_c(query, stmt->query_template[i]);
+		}
+	}
+	if (arg_pos != args_count) {
+		i_panic("lib-sql: Too many bind args (%u) for statement: %s",
+			args_count, stmt->query_template);
+	}
+	return str_c(query);
+}
+
+static void
+default_sql_statement_query(struct sql_statement *stmt,
+			    sql_query_callback_t *callback, void *context)
+{
+	sql_query(stmt->db, sql_statement_get_query(stmt),
+		  callback, context);
+	pool_unref(&stmt->pool);
+}
+
+static struct sql_result *
+default_sql_statement_query_s(struct sql_statement *stmt)
+{
+	struct sql_result *result =
+		sql_query_s(stmt->db, sql_statement_get_query(stmt));
+	pool_unref(&stmt->pool);
+	return result;
+}
+
+static void default_sql_update_stmt(struct sql_transaction_context *ctx,
+				    struct sql_statement *stmt,
+				    unsigned int *affected_rows)
+{
+	ctx->db->v.update(ctx, sql_statement_get_query(stmt),
+			  affected_rows);
+	pool_unref(&stmt->pool);
+}
+
+struct sql_prepared_statement *
+sql_prepared_statement_init(struct sql_db *db, const char *query_template)
+{
+	struct sql_prepared_statement *stmt;
+
+	stmt = hash_table_lookup(db->prepared_stmt_hash, query_template);
+	if (stmt != NULL) {
+		stmt->refcount++;
+		return stmt;
+	}
+
+	if (db->v.prepared_statement_init != NULL)
+		stmt = db->v.prepared_statement_init(db, query_template);
+	else
+		stmt = default_sql_prepared_statement_init(db, query_template);
+
+	hash_table_insert(db->prepared_stmt_hash, stmt->query_template, stmt);
+	return stmt;
+}
+
+void sql_prepared_statement_unref(struct sql_prepared_statement **_prep_stmt)
+{
+	struct sql_prepared_statement *prep_stmt = *_prep_stmt;
+
+	*_prep_stmt = NULL;
+
+	i_assert(prep_stmt->refcount > 0);
+	prep_stmt->refcount--;
+}
+
+static void
+sql_statement_init_fields(struct sql_statement *stmt, struct sql_db *db)
+{
+	stmt->db = db;
+	p_array_init(&stmt->args, stmt->pool, 8);
+}
+
+struct sql_statement *
+sql_statement_init(struct sql_db *db, const char *query_template)
+{
+	struct sql_statement *stmt;
+
+	if (db->v.statement_init != NULL)
+		stmt = db->v.statement_init(db, query_template);
+	else {
+		pool_t pool = pool_alloconly_create("sql statement", 1024);
+		stmt = p_new(pool, struct sql_statement, 1);
+		stmt->pool = pool;
+	}
+	stmt->query_template = p_strdup(stmt->pool, query_template);
+	sql_statement_init_fields(stmt, db);
+	return stmt;
+}
+
+struct sql_statement *
+sql_statement_init_prepared(struct sql_prepared_statement *prep_stmt)
+{
+	struct sql_statement *stmt;
+
+	if (prep_stmt->db->v.statement_init_prepared == NULL)
+		return default_sql_statement_init_prepared(prep_stmt);
+
+	stmt = prep_stmt->db->v.statement_init_prepared(prep_stmt);
+	sql_statement_init_fields(stmt, prep_stmt->db);
+	return stmt;
+}
+
+void sql_statement_abort(struct sql_statement **_stmt)
+{
+	struct sql_statement *stmt = *_stmt;
+
+	*_stmt = NULL;
+	if (stmt->db->v.statement_abort != NULL)
+		stmt->db->v.statement_abort(stmt);
+	pool_unref(&stmt->pool);
+}
+
+void sql_statement_set_timestamp(struct sql_statement *stmt,
+				 const struct timespec *ts)
+{
+	if (stmt->db->v.statement_set_timestamp != NULL)
+		stmt->db->v.statement_set_timestamp(stmt, ts);
+}
+
+void sql_statement_bind_str(struct sql_statement *stmt,
+			    unsigned int column_idx, const char *value)
+{
+	const char *escaped_value =
+		p_strdup_printf(stmt->pool, "'%s'",
+				sql_escape_string(stmt->db, value));
+	array_idx_set(&stmt->args, column_idx, &escaped_value);
+
+	if (stmt->db->v.statement_bind_str != NULL)
+		stmt->db->v.statement_bind_str(stmt, column_idx, value);
+}
+
+void sql_statement_bind_binary(struct sql_statement *stmt,
+			       unsigned int column_idx, const void *value,
+			       size_t value_size)
+{
+	const char *value_str =
+		p_strdup_printf(stmt->pool, "%s",
+				sql_escape_blob(stmt->db, value, value_size));
+	array_idx_set(&stmt->args, column_idx, &value_str);
+
+	if (stmt->db->v.statement_bind_binary != NULL) {
+		stmt->db->v.statement_bind_binary(stmt, column_idx,
+						  value, value_size);
+	}
+}
+
+void sql_statement_bind_int64(struct sql_statement *stmt,
+			      unsigned int column_idx, int64_t value)
+{
+	const char *value_str = p_strdup_printf(stmt->pool, "%"PRId64, value);
+	array_idx_set(&stmt->args, column_idx, &value_str);
+
+	if (stmt->db->v.statement_bind_int64 != NULL)
+		stmt->db->v.statement_bind_int64(stmt, column_idx, value);
+}
+
+#undef sql_statement_query
+void sql_statement_query(struct sql_statement **_stmt,
+			 sql_query_callback_t *callback, void *context)
+{
+	struct sql_statement *stmt = *_stmt;
+
+	*_stmt = NULL;
+	if (stmt->db->v.statement_query != NULL)
+		stmt->db->v.statement_query(stmt, callback, context);
+	else
+		default_sql_statement_query(stmt, callback, context);
+}
+
+struct sql_result *sql_statement_query_s(struct sql_statement **_stmt)
+{
+	struct sql_statement *stmt = *_stmt;
+
+	*_stmt = NULL;
+	if (stmt->db->v.statement_query_s != NULL)
+		return stmt->db->v.statement_query_s(stmt);
+	else
+		return default_sql_statement_query_s(stmt);
+}
+
+void sql_result_ref(struct sql_result *result)
+{
+	result->refcount++;
+}
+
+void sql_result_unref(struct sql_result *result)
+{
+	i_assert(result->refcount > 0);
+	if (--result->refcount > 0)
+		return;
+
+	i_free(result->map);
+	result->v.free(result);
+}
+
+static const struct sql_field_def *
+sql_field_def_find(const struct sql_field_def *fields, const char *name)
+{
+	unsigned int i;
+
+	for (i = 0; fields[i].name != NULL; i++) {
+		if (strcasecmp(fields[i].name, name) == 0)
+			return &fields[i];
+	}
+	return NULL;
+}
+
+static void
+sql_result_build_map(struct sql_result *result,
+		     const struct sql_field_def *fields, size_t dest_size)
+{
+	const struct sql_field_def *def;
+	const char *name;
+	unsigned int i, count, field_size = 0;
+
+	count = sql_result_get_fields_count(result);
+
+	result->map_size = count;
+	result->map = i_new(struct sql_field_map, result->map_size);
+	for (i = 0; i < count; i++) {
+		name = sql_result_get_field_name(result, i);
+		def = sql_field_def_find(fields, name);
+		if (def != NULL) {
+			result->map[i].type = def->type;
+			result->map[i].offset = def->offset;
+			switch (def->type) {
+			case SQL_TYPE_STR:
+				field_size = sizeof(const char *);
+				break;
+			case SQL_TYPE_UINT:
+				field_size = sizeof(unsigned int);
+				break;
+			case SQL_TYPE_ULLONG:
+				field_size = sizeof(unsigned long long);
+				break;
+			case SQL_TYPE_BOOL:
+				field_size = sizeof(bool);
+				break;
+			}
+			i_assert(def->offset + field_size <= dest_size);
+		} else {
+			result->map[i].offset = SIZE_MAX;
+		}
+	}
+}
+
+void sql_result_setup_fetch(struct sql_result *result,
+			    const struct sql_field_def *fields,
+			    void *dest, size_t dest_size)
+{
+	if (result->map == NULL)
+		sql_result_build_map(result, fields, dest_size);
+	result->fetch_dest = dest;
+	result->fetch_dest_size = dest_size;
+}
+
+static void sql_result_fetch(struct sql_result *result)
+{
+	unsigned int i, count;
+	const char *value;
+	void *ptr;
+
+	memset(result->fetch_dest, 0, result->fetch_dest_size);
+	count = result->map_size;
+	for (i = 0; i < count; i++) {
+		if (result->map[i].offset == SIZE_MAX)
+			continue;
+
+		value = sql_result_get_field_value(result, i);
+		ptr = STRUCT_MEMBER_P(result->fetch_dest,
+				      result->map[i].offset);
+
+		switch (result->map[i].type) {
+		case SQL_TYPE_STR: {
+			*((const char **)ptr) = value;
+			break;
+		}
+		case SQL_TYPE_UINT: {
+			if (value != NULL &&
+			    str_to_uint(value, (unsigned int *)ptr) < 0)
+				i_error("sql: Value not uint: %s", value);
+			break;
+		}
+		case SQL_TYPE_ULLONG: {
+			if (value != NULL &&
+			    str_to_ullong(value, (unsigned long long *)ptr) < 0)
+				i_error("sql: Value not ullong: %s", value);
+			break;
+		}
+		case SQL_TYPE_BOOL: {
+			if (value != NULL && (*value == 't' || *value == '1'))
+				*((bool *)ptr) = TRUE;
+			break;
+		}
+		}
+	}
+}
+
+int sql_result_next_row(struct sql_result *result)
+{
+	int ret;
+
+	if ((ret = result->v.next_row(result)) <= 0)
+		return ret;
+
+	if (result->fetch_dest != NULL)
+		sql_result_fetch(result);
+	return 1;
+}
+
+#undef sql_result_more
+void sql_result_more(struct sql_result **result,
+		     sql_query_callback_t *callback, void *context)
+{
+	i_assert((*result)->v.more != NULL);
+
+	(*result)->v.more(result, TRUE, callback, context);
+}
+
+static void
+sql_result_more_sync_callback(struct sql_result *result, void *context)
+{
+	struct sql_result **dest_result = context;
+
+	*dest_result = result;
+}
+
+void sql_result_more_s(struct sql_result **result)
+{
+	i_assert((*result)->v.more != NULL);
+
+	(*result)->v.more(result, FALSE, sql_result_more_sync_callback, result);
+	/* the callback must have been called */
+	i_assert(*result != NULL);
+}
+
+unsigned int sql_result_get_fields_count(struct sql_result *result)
+{
+	return result->v.get_fields_count(result);
+}
+
+const char *sql_result_get_field_name(struct sql_result *result,
+				      unsigned int idx)
+{
+	return result->v.get_field_name(result, idx);
+}
+
+int sql_result_find_field(struct sql_result *result, const char *field_name)
+{
+	return result->v.find_field(result, field_name);
+}
+
+const char *sql_result_get_field_value(struct sql_result *result,
+				       unsigned int idx)
+{
+	return result->v.get_field_value(result, idx);
+}
+
+const unsigned char *
+sql_result_get_field_value_binary(struct sql_result *result,
+				  unsigned int idx, size_t *size_r)
+{
+	return result->v.get_field_value_binary(result, idx, size_r);
+}
+
+const char *sql_result_find_field_value(struct sql_result *result,
+					const char *field_name)
+{
+	return result->v.find_field_value(result, field_name);
+}
+
+const char *const *sql_result_get_values(struct sql_result *result)
+{
+	return result->v.get_values(result);
+}
+
+const char *sql_result_get_error(struct sql_result *result)
+{
+	return result->v.get_error(result);
+}
+
+enum sql_result_error_type sql_result_get_error_type(struct sql_result *result)
+{
+	return result->error_type;
+}
+
+static void
+sql_result_not_connected_free(struct sql_result *result ATTR_UNUSED)
+{
+}
+
+static int
+sql_result_not_connected_next_row(struct sql_result *result ATTR_UNUSED)
+{
+	return -1;
+}
+
+static const char *
+sql_result_not_connected_get_error(struct sql_result *result ATTR_UNUSED)
+{
+	return SQL_ERRSTR_NOT_CONNECTED;
+}
+
+struct sql_transaction_context *sql_transaction_begin(struct sql_db *db)
+{
+	return db->v.transaction_begin(db);
+}
+
+#undef sql_transaction_commit
+void sql_transaction_commit(struct sql_transaction_context **_ctx,
+			    sql_commit_callback_t *callback, void *context)
+{
+	struct sql_transaction_context *ctx = *_ctx;
+
+	*_ctx = NULL;
+	ctx->db->v.transaction_commit(ctx, callback, context);
+}
+
+int sql_transaction_commit_s(struct sql_transaction_context **_ctx,
+			     const char **error_r)
+{
+	struct sql_transaction_context *ctx = *_ctx;
+
+	*_ctx = NULL;
+	return ctx->db->v.transaction_commit_s(ctx, error_r);
+}
+
+void sql_transaction_rollback(struct sql_transaction_context **_ctx)
+{
+	struct sql_transaction_context *ctx = *_ctx;
+
+	*_ctx = NULL;
+	ctx->db->v.transaction_rollback(ctx);
+}
+
+void sql_update(struct sql_transaction_context *ctx, const char *query)
+{
+	ctx->db->v.update(ctx, query, NULL);
+}
+
+void sql_update_stmt(struct sql_transaction_context *ctx,
+		     struct sql_statement **_stmt)
+{
+	struct sql_statement *stmt = *_stmt;
+
+	*_stmt = NULL;
+	if (ctx->db->v.update_stmt != NULL)
+		ctx->db->v.update_stmt(ctx, stmt, NULL);
+	else
+		default_sql_update_stmt(ctx, stmt, NULL);
+}
+
+void sql_update_get_rows(struct sql_transaction_context *ctx, const char *query,
+			 unsigned int *affected_rows)
+{
+	ctx->db->v.update(ctx, query, affected_rows);
+}
+
+void sql_update_stmt_get_rows(struct sql_transaction_context *ctx,
+			      struct sql_statement **_stmt,
+			      unsigned int *affected_rows)
+{
+	struct sql_statement *stmt = *_stmt;
+
+	*_stmt = NULL;
+	if (ctx->db->v.update_stmt != NULL)
+		ctx->db->v.update_stmt(ctx, stmt, affected_rows);
+	else
+		default_sql_update_stmt(ctx, stmt, affected_rows);
+}
+
+void sql_db_set_state(struct sql_db *db, enum sql_db_state state)
+{
+	enum sql_db_state old_state = db->state;
+
+	if (db->state == state)
+		return;
+
+	db->state = state;
+	if (db->state_change_callback != NULL) {
+		db->state_change_callback(db, old_state,
+					  db->state_change_context);
+	}
+}
+
+void sql_transaction_add_query(struct sql_transaction_context *ctx, pool_t pool,
+			       const char *query, unsigned int *affected_rows)
+{
+	struct sql_transaction_query *tquery;
+
+	tquery = p_new(pool, struct sql_transaction_query, 1);
+	tquery->trans = ctx;
+	tquery->query = p_strdup(pool, query);
+	tquery->affected_rows = affected_rows;
+
+	if (ctx->head == NULL)
+		ctx->head = tquery;
+	else
+		ctx->tail->next = tquery;
+	ctx->tail = tquery;
+}
+
+void sql_connection_log_finished(struct sql_db *db)
+{
+	struct event_passthrough *e = event_create_passthrough(db->event)->
+		set_name(SQL_CONNECTION_FINISHED);
+	e_debug(e->event(),
+		"Connection finished (queries=%"PRIu64", slow queries=%"PRIu64")",
+		db->succeeded_queries + db->failed_queries,
+		db->slow_queries);
+}
+
+struct event_passthrough *
+sql_query_finished_event(struct sql_db *db, struct event *event, const char *query,
+			 bool success, int *duration_r)
+{
+	int diff;
+	struct timeval tv;
+	event_get_create_time(event, &tv);
+	struct event_passthrough *e = event_create_passthrough(event)->
+			set_name(SQL_QUERY_FINISHED)->
+			add_str("query_first_word", t_strcut(query, ' '));
+	diff = timeval_diff_msecs(&ioloop_timeval, &tv);
+
+	if (!success) {
+		db->failed_queries++;
+	} else {
+		db->succeeded_queries++;
+	}
+
+	if (diff >= SQL_SLOW_QUERY_MSEC) {
+		e->add_str("slow_query", "y");
+		db->slow_queries++;
+	}
+
+	if (duration_r != NULL)
+		*duration_r = diff;
+
+	return e;
+}
+
+struct event_passthrough *sql_transaction_finished_event(struct sql_transaction_context *ctx)
+{
+	return event_create_passthrough(ctx->event)->
+		set_name(SQL_TRANSACTION_FINISHED);
+}
+
+void sql_wait(struct sql_db *db)
+{
+	if (db->v.wait != NULL)
+		db->v.wait(db);
+}
+
+
+struct sql_result sql_not_connected_result = {
+	.v = {
+		sql_result_not_connected_free,
+		sql_result_not_connected_next_row,
+		NULL, NULL, NULL, NULL, NULL, NULL, NULL,
+		sql_result_not_connected_get_error,
+		NULL,
+	},
+	.failed_try_retry = TRUE
+};
diff --git a/src/lib-sql/sql-api.h b/src/lib-sql/sql-api.h
new file mode 100644
index 0000000..7936b98
--- /dev/null
+++ b/src/lib-sql/sql-api.h
@@ -0,0 +1,249 @@
+#ifndef SQL_API_H
+#define SQL_API_H
+
+struct timespec;
+
+/* This SQL API is designed to work asynchronously. The underlying drivers
+   however may not. */
+
+enum sql_db_flags {
+	/* Set if queries are not executed asynchronously */
+	SQL_DB_FLAG_BLOCKING		= 0x01,
+	/* Set if database wants to use connection pooling */
+	SQL_DB_FLAG_POOLED		= 0x02,
+	/* Prepared statements are supported by the database. If they aren't,
+	   the functions can still be used, but they're just internally
+	   convered into regular statements. */
+	SQL_DB_FLAG_PREP_STATEMENTS	= 0x04,
+	/* Database supports INSERT .. ON DUPLICATE KEY syntax. */
+	SQL_DB_FLAG_ON_DUPLICATE_KEY	= 0x08,
+	/* Database supports INSERT .. ON CONFLICT DO UPDATE syntax. */
+	SQL_DB_FLAG_ON_CONFLICT_DO	= 0x10,
+};
+
+enum sql_field_type {
+	SQL_TYPE_STR,
+	SQL_TYPE_UINT,
+	SQL_TYPE_ULLONG,
+	SQL_TYPE_BOOL
+};
+
+struct sql_field_def {
+	enum sql_field_type type;
+	const char *name;
+	size_t offset;
+};
+
+enum sql_result_error_type {
+	SQL_RESULT_ERROR_TYPE_UNKNOWN = 0,
+	/* It's unknown whether write succeeded or not. This could be due to
+	   a timeout or a disconnection from server. */
+	SQL_RESULT_ERROR_TYPE_WRITE_UNCERTAIN
+};
+
+enum sql_result_next {
+	/* Row was returned */
+	SQL_RESULT_NEXT_OK = 1,
+	/* There are no more rows */
+	SQL_RESULT_NEXT_LAST = 0,
+	/* Error occurred - see sql_result_get_error*() */
+	SQL_RESULT_NEXT_ERROR = -1,
+	/* There are more results - call sql_result_more() */
+	SQL_RESULT_NEXT_MORE = -99
+};
+
+#define SQL_DEF_STRUCT(name, struct_name, type, c_type) \
+	{ (type) + COMPILE_ERROR_IF_TYPES_NOT_COMPATIBLE( \
+		((struct struct_name *)0)->name, c_type), \
+	  #name, offsetof(struct struct_name, name) }
+
+#define SQL_DEF_STRUCT_STR(name, struct_name) \
+	SQL_DEF_STRUCT(name, struct_name, SQL_TYPE_STR, const char *)
+#define SQL_DEF_STRUCT_UINT(name, struct_name) \
+	SQL_DEF_STRUCT(name, struct_name, SQL_TYPE_UINT, unsigned int)
+#define SQL_DEF_STRUCT_ULLONG(name, struct_name) \
+	SQL_DEF_STRUCT(name, struct_name, SQL_TYPE_ULLONG, unsigned long long)
+#define SQL_DEF_STRUCT_BOOL(name, struct_name) \
+	SQL_DEF_STRUCT(name, struct_name, SQL_TYPE_BOOL, bool)
+
+struct sql_db;
+struct sql_result;
+
+struct sql_commit_result {
+	const char *error;
+	enum sql_result_error_type error_type;
+};
+
+struct sql_settings {
+	const char *driver;
+	const char *connect_string;
+	struct event *event_parent;
+};
+
+typedef void sql_query_callback_t(struct sql_result *result, void *context);
+typedef void sql_commit_callback_t(const struct sql_commit_result *result, void *context);
+
+void sql_drivers_init(void);
+void sql_drivers_deinit(void);
+
+/* register all built-in SQL drivers */
+void sql_drivers_register_all(void);
+
+void sql_driver_register(const struct sql_db *driver);
+void sql_driver_unregister(const struct sql_db *driver);
+
+/* Initialize database connections. db_driver is the database driver name,
+   eg. "mysql" or "pgsql". connect_string is driver-specific. */
+struct sql_db *sql_init(const char *db_driver, const char *connect_string);
+int sql_init_full(const struct sql_settings *set, struct sql_db **db_r,
+		  const char **error_r);
+
+void sql_ref(struct sql_db *db);
+void sql_unref(struct sql_db **db);
+
+/* Returns SQL database state flags. */
+enum sql_db_flags sql_get_flags(struct sql_db *db);
+
+/* Explicitly connect to the database. It's not required to call this function
+   though. Returns -1 if we're not connected, 0 if we started connecting or
+   1 if we are fully connected now. */
+int sql_connect(struct sql_db *db);
+/* Explicitly disconnect from database and abort pending auth requests. */
+void sql_disconnect(struct sql_db *db);
+
+/* Escape the given string if needed and return it. */
+const char *sql_escape_string(struct sql_db *db, const char *string);
+/* Escape the given data as a string. */
+const char *sql_escape_blob(struct sql_db *db,
+			    const unsigned char *data, size_t size);
+
+/* Execute SQL query without waiting for results. */
+void sql_exec(struct sql_db *db, const char *query);
+/* Execute SQL query and return result in callback. If fields list is given,
+   the returned fields are validated to be of correct type, and you can use
+   sql_result_next_row_get() */
+void sql_query(struct sql_db *db, const char *query,
+	       sql_query_callback_t *callback, void *context);
+#define sql_query(db, query, callback, context) \
+	sql_query(db, query - \
+		CALLBACK_TYPECHECK(callback, void (*)( \
+			struct sql_result *, typeof(context))), \
+		(sql_query_callback_t *)callback, context)
+/* Execute blocking SQL query and return result. */
+struct sql_result *sql_query_s(struct sql_db *db, const char *query);
+
+struct sql_prepared_statement *
+sql_prepared_statement_init(struct sql_db *db, const char *query_template);
+void sql_prepared_statement_unref(struct sql_prepared_statement **prep_stmt);
+
+struct sql_statement *
+sql_statement_init(struct sql_db *db, const char *query_template);
+struct sql_statement *
+sql_statement_init_prepared(struct sql_prepared_statement *prep_stmt);
+void sql_statement_abort(struct sql_statement **stmt);
+void sql_statement_set_timestamp(struct sql_statement *stmt,
+				 const struct timespec *ts);
+void sql_statement_bind_str(struct sql_statement *stmt,
+			    unsigned int column_idx, const char *value);
+void sql_statement_bind_binary(struct sql_statement *stmt,
+			       unsigned int column_idx, const void *value,
+			       size_t value_size);
+void sql_statement_bind_int64(struct sql_statement *stmt,
+			      unsigned int column_idx, int64_t value);
+void sql_statement_query(struct sql_statement **stmt,
+			 sql_query_callback_t *callback, void *context);
+#define sql_statement_query(stmt, callback, context) \
+	sql_statement_query(stmt, \
+		(sql_query_callback_t *)callback, TRUE ? context : \
+		CALLBACK_TYPECHECK(callback, void (*)( \
+			struct sql_result *, typeof(context))))
+struct sql_result *sql_statement_query_s(struct sql_statement **stmt);
+
+void sql_result_setup_fetch(struct sql_result *result,
+			    const struct sql_field_def *fields,
+			    void *dest, size_t dest_size);
+
+/* Go to next row. See enum sql_result_next. */
+int sql_result_next_row(struct sql_result *result);
+
+/* If sql_result_next_row() returned SQL_RESULT_NEXT_MORE, this can be called
+   to continue returning more results. The result is freed with this call, so
+   it must not be accesed anymore until the callback is finished. */
+void sql_result_more(struct sql_result **result,
+		     sql_query_callback_t *callback, void *context);
+#define sql_result_more(result, callback, context) \
+	sql_result_more(result - \
+		CALLBACK_TYPECHECK(callback, void (*)( \
+			struct sql_result *, typeof(context))), \
+		(sql_query_callback_t *)callback, context)
+/* Synchronous version of sql_result_more(). The result will be replaced with
+   the new result. */
+void sql_result_more_s(struct sql_result **result);
+
+void sql_result_ref(struct sql_result *result);
+/* Needs to be called only with sql_query_s() or when result has been
+   explicitly referenced. */
+void sql_result_unref(struct sql_result *result);
+
+/* Return number of fields in result. */
+unsigned int sql_result_get_fields_count(struct sql_result *result);
+/* Return name of the given field index. */
+const char *sql_result_get_field_name(struct sql_result *result,
+				      unsigned int idx);
+/* Return field index for given name, or -1 if not found. */
+int sql_result_find_field(struct sql_result *result, const char *field_name);
+
+/* Returns value of given field as string. Note that it can be NULL. */
+const char *sql_result_get_field_value(struct sql_result *result,
+				       unsigned int idx);
+/* Returns a binary value. Note that a NULL is returned as NULL with size=0,
+   while empty string returns non-NULL with size=0. */
+const unsigned char *
+sql_result_get_field_value_binary(struct sql_result *result,
+				  unsigned int idx, size_t *size_r);
+/* Find the field and return its value. NULL return value can mean that either
+   the field didn't exist or that its value is NULL. */
+const char *sql_result_find_field_value(struct sql_result *result,
+					const char *field_name);
+/* Return all values of current row. Note that this array is not
+   NULL-terminated - you must use sql_result_get_fields_count() to find out
+   the array's length. It's also possible that some of the values inside the
+   array are NULL. */
+const char *const *sql_result_get_values(struct sql_result *result);
+
+/* Return last error message in result. */
+const char *sql_result_get_error(struct sql_result *result);
+enum sql_result_error_type sql_result_get_error_type(struct sql_result *result);
+
+/* Begin a new transaction. Currently you're limited to only one open
+   transaction at a time. */
+struct sql_transaction_context *sql_transaction_begin(struct sql_db *db);
+/* Commit transaction. */
+void sql_transaction_commit(struct sql_transaction_context **ctx,
+			    sql_commit_callback_t *callback, void *context);
+#define sql_transaction_commit(ctx, callback, context) \
+	  sql_transaction_commit(ctx - \
+		CALLBACK_TYPECHECK(callback, void (*)( \
+			const struct sql_commit_result *, typeof(context))), \
+		(sql_commit_callback_t *)callback, context)
+/* Synchronous commit. Returns 0 if ok, -1 if error. */
+int sql_transaction_commit_s(struct sql_transaction_context **ctx,
+			     const char **error_r);
+void sql_transaction_rollback(struct sql_transaction_context **ctx);
+
+/* Execute query in given transaction. */
+void sql_update(struct sql_transaction_context *ctx, const char *query);
+void sql_update_stmt(struct sql_transaction_context *ctx,
+		     struct sql_statement **stmt);
+/* Save the number of rows updated by this query. The value is set before
+   commit callback is called. */
+void sql_update_get_rows(struct sql_transaction_context *ctx, const char *query,
+			 unsigned int *affected_rows);
+void sql_update_stmt_get_rows(struct sql_transaction_context *ctx,
+			      struct sql_statement **stmt,
+			      unsigned int *affected_rows);
+
+/* Wait for SQL query results. */
+void sql_wait(struct sql_db *db);
+
+#endif
diff --git a/src/lib-sql/sql-db-cache.c b/src/lib-sql/sql-db-cache.c
new file mode 100644
index 0000000..b2fb9fb
--- /dev/null
+++ b/src/lib-sql/sql-db-cache.c
@@ -0,0 +1,156 @@
+/* Copyright (c) 2004-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "array.h"
+#include "hash.h"
+#include "sql-api-private.h"
+#include "sql-db-cache.h"
+
+#define SQL_DB_CACHE_CONTEXT(obj) \
+	MODULE_CONTEXT_REQUIRE(obj, sql_db_cache_module)
+
+struct sql_db_cache_context {
+	union sql_db_module_context module_ctx;
+	struct sql_db *prev, *next; /* These are set while refcount=0 */
+
+	struct sql_db_cache *cache;
+	int refcount;
+	char *key;
+	void (*orig_deinit)(struct sql_db *db);
+};
+
+struct sql_db_cache {
+	HASH_TABLE(char *, struct sql_db *) dbs;
+	unsigned int unused_count, max_unused_connections;
+	struct sql_db *unused_tail, *unused_head;
+};
+
+static MODULE_CONTEXT_DEFINE_INIT(sql_db_cache_module, &sql_db_module_register);
+
+static void sql_db_cache_db_unref(struct sql_db *db)
+{
+	struct sql_db_cache_context *ctx = SQL_DB_CACHE_CONTEXT(db);
+	struct sql_db_cache_context *head_ctx;
+
+	if (--ctx->refcount > 0)
+		return;
+
+	i_assert(db->refcount == 2);
+
+	ctx->cache->unused_count++;
+	if (ctx->cache->unused_tail == NULL)
+		ctx->cache->unused_tail = db;
+	else {
+		head_ctx = SQL_DB_CACHE_CONTEXT(ctx->cache->unused_head);
+		head_ctx->next = db;
+	}
+	ctx->prev = ctx->cache->unused_head;
+	ctx->cache->unused_head = db;
+}
+
+static void sql_db_cache_unlink(struct sql_db_cache_context *ctx)
+{
+	struct sql_db_cache_context *prev_ctx, *next_ctx;
+
+	i_assert(ctx->refcount == 0);
+
+	if (ctx->prev == NULL)
+		ctx->cache->unused_tail = ctx->next;
+	else {
+		prev_ctx = SQL_DB_CACHE_CONTEXT(ctx->prev);
+		prev_ctx->next = ctx->next;
+	}
+	if (ctx->next == NULL)
+		ctx->cache->unused_head = ctx->prev;
+	else {
+		next_ctx = SQL_DB_CACHE_CONTEXT(ctx->next);
+		next_ctx->prev = ctx->prev;
+	}
+	ctx->cache->unused_count--;
+}
+
+static void sql_db_cache_free_tail(struct sql_db_cache *cache)
+{
+	struct sql_db *db;
+	struct sql_db_cache_context *ctx;
+
+	db = cache->unused_tail;
+	i_assert(db->refcount == 1);
+
+	ctx = SQL_DB_CACHE_CONTEXT(db);
+	sql_db_cache_unlink(ctx);
+	hash_table_remove(cache->dbs, ctx->key);
+
+	i_free(ctx->key);
+	i_free(ctx);
+
+	db->v.unref = NULL;
+	sql_unref(&db);
+}
+
+static void sql_db_cache_drop_oldest(struct sql_db_cache *cache)
+{
+	while (cache->unused_count >= cache->max_unused_connections)
+		sql_db_cache_free_tail(cache);
+}
+
+int sql_db_cache_new(struct sql_db_cache *cache, const struct sql_settings *set,
+		     struct sql_db **db_r, const char **error_r)
+{
+	struct sql_db_cache_context *ctx;
+	struct sql_db *db;
+	char *key;
+
+	key = i_strdup_printf("%s\t%s", set->driver, set->connect_string);
+	db = hash_table_lookup(cache->dbs, key);
+	if (db != NULL) {
+		ctx = SQL_DB_CACHE_CONTEXT(db);
+		if (ctx->refcount == 0) {
+			sql_db_cache_unlink(ctx);
+			ctx->prev = ctx->next = NULL;
+		}
+		i_free(key);
+	} else {
+		sql_db_cache_drop_oldest(cache);
+
+		if (sql_init_full(set, &db, error_r) < 0) {
+			i_free(key);
+			return -1;
+		}
+
+		ctx = i_new(struct sql_db_cache_context, 1);
+		ctx->cache = cache;
+		ctx->key = key;
+		ctx->orig_deinit = db->v.deinit;
+		db->v.unref = sql_db_cache_db_unref;
+
+		MODULE_CONTEXT_SET(db, sql_db_cache_module, ctx);
+		hash_table_insert(cache->dbs, ctx->key, db);
+	}
+
+	ctx->refcount++;
+	sql_ref(db);
+	*db_r = db;
+	return 0;
+}
+
+struct sql_db_cache *sql_db_cache_init(unsigned int max_unused_connections)
+{
+	struct sql_db_cache *cache;
+
+	cache = i_new(struct sql_db_cache, 1);
+	hash_table_create(&cache->dbs, default_pool, 0, str_hash, strcmp);
+	cache->max_unused_connections = max_unused_connections;
+	return cache;
+}
+
+void sql_db_cache_deinit(struct sql_db_cache **_cache)
+{
+	struct sql_db_cache *cache = *_cache;
+
+	*_cache = NULL;
+	while (cache->unused_tail != NULL)
+		sql_db_cache_free_tail(cache);
+	hash_table_destroy(&cache->dbs);
+	i_free(cache);
+}
diff --git a/src/lib-sql/sql-db-cache.h b/src/lib-sql/sql-db-cache.h
new file mode 100644
index 0000000..1517f5f
--- /dev/null
+++ b/src/lib-sql/sql-db-cache.h
@@ -0,0 +1,13 @@
+#ifndef SQL_DB_CACHE_H
+#define SQL_DB_CACHE_H
+
+struct sql_db_cache;
+
+/* Like sql_init(), but use a connection pool. */
+int sql_db_cache_new(struct sql_db_cache *cache, const struct sql_settings *set,
+		      struct sql_db **db_r, const char **error_r);
+
+struct sql_db_cache *sql_db_cache_init(unsigned int max_unused_connections);
+void sql_db_cache_deinit(struct sql_db_cache **cache);
+
+#endif