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diff --git a/README_FILES/CDB_README b/README_FILES/CDB_README new file mode 100644 index 0000000..0f06d47 --- /dev/null +++ b/README_FILES/CDB_README @@ -0,0 +1,74 @@ +PPoossttffiixx CCDDBB HHoowwttoo + +------------------------------------------------------------------------------- + +IInnttrroodduuccttiioonn + +CDB (Constant DataBase) is an indexed file format designed by Daniel Bernstein. +CDB is optimized exclusively for read access and guarantees that each record +will be read in at most two disk accesses. This is achieved by forgoing support +for incremental updates: no single-record inserts or deletes are supported. CDB +databases can be modified only by rebuilding them completely from scratch, +hence the "constant" qualifier in the name. + +Postfix CDB databases are specified as "cdb:name", where name specifies the CDB +file name without the ".cdb" suffix (another suffix, ".tmp", is used +temporarily while a CDB file is under construction). CDB databases are +maintained with the postmap(1) or postalias(1) command. The DATABASE_README +document has general information about Postfix databases. + +CDB support is available with Postfix 2.2 and later releases. This document +describes how to build Postfix with CDB support. + +BBuuiillddiinngg PPoossttffiixx wwiitthh CCDDBB ssuuppppoorrtt + +These instructions assume that you build Postfix from source code as described +in the INSTALL document. Some modification may be required if you build Postfix +from a vendor-specific source package. + +Postfix is compatible with two CDB implementations: + + * The original cdb library from Daniel Bernstein, available from http:// + cr.yp.to/cdb.html, and + + * tinycdb (version 0.5 and later) from Michael Tokarev, available from http:/ + /www.corpit.ru/mjt/tinycdb.html. + +Tinycdb is preferred, since it is a bit faster, has additional useful +functionality and is much simpler to use. + +To build Postfix after you have installed tinycdb, use something like: + + % make tidy + % CDB=../../../tinycdb-0.5 + % make -f Makefile.init makefiles "CCARGS=-DHAS_CDB -I$CDB" \ + "AUXLIBS_CDB=$CDB/libcdb.a" + % make + +Alternatively, for the D.J.B. version of CDB: + + % make tidy + % CDB=../../../cdb-0.75 + % make -f Makefile.init makefiles "CCARGS=-DHAS_CDB -I$CDB" \ + "AUXLIBS_CDB=$CDB/cdb.a $CDB/alloc.a $CDB/buffer.a $CDB/unix.a $CDB/ + byte.a" + % make + +Postfix versions before 3.0 use AUXLIBS instead of AUXLIBS_CDB. With Postfix +3.0 and later, the old AUXLIBS variable still supports building a statically- +loaded CDB database client, but only the new AUXLIBS_CDB variable supports +building a dynamically-loaded or statically-loaded CDB database client. + + Failure to use the AUXLIBS_CDB variable will defeat the purpose of dynamic + database client loading. Every Postfix executable file will have CDB + database library dependencies. And that was exactly what dynamic database + client loading was meant to avoid. + +After Postfix has been built with cdb support, you can use "cdb" tables +wherever you can use read-only "hash", "btree" or "dbm" tables. However, the +"ppoossttmmaapp --ii" (incremental record insertion) and "ppoossttmmaapp --dd" (incremental +record deletion) command-line options are not available. For the same reason +the "cdb" map type cannot be used to store the persistent address verification +cache for the verify(8) service, or to store TLS session information for the +tlsmgr(8) service. + |