6 files changed, 108 insertions, 0 deletions
diff --git a/contrib/pg_freespacemap/Makefile b/contrib/pg_freespacemap/Makefile
new file mode 100644
index 0000000..da40b80
--- /dev/null
+++ b/contrib/pg_freespacemap/Makefile
@@ -0,0 +1,22 @@
+# contrib/pg_freespacemap/Makefile
+
+MODULE_big = pg_freespacemap
+OBJS = \
+	$(WIN32RES) \
+	pg_freespacemap.o
+
+EXTENSION = pg_freespacemap
+DATA = pg_freespacemap--1.1.sql pg_freespacemap--1.1--1.2.sql \
+	pg_freespacemap--1.0--1.1.sql
+PGFILEDESC = "pg_freespacemap - monitoring of free space map"
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/pg_freespacemap
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/pg_freespacemap/pg_freespacemap--1.0--1.1.sql b/contrib/pg_freespacemap/pg_freespacemap--1.0--1.1.sql
new file mode 100644
index 0000000..52d6576
--- /dev/null
+++ b/contrib/pg_freespacemap/pg_freespacemap--1.0--1.1.sql
@@ -0,0 +1,7 @@
+/* contrib/pg_freespacemap/pg_freespacemap--1.0--1.1.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION pg_freespacemap UPDATE TO '1.1'" to load this file. \quit
+
+ALTER FUNCTION pg_freespace(regclass, bigint) PARALLEL SAFE;
+ALTER FUNCTION pg_freespace(regclass) PARALLEL SAFE;
diff --git a/contrib/pg_freespacemap/pg_freespacemap--1.1--1.2.sql b/contrib/pg_freespacemap/pg_freespacemap--1.1--1.2.sql
new file mode 100644
index 0000000..f558def
--- /dev/null
+++ b/contrib/pg_freespacemap/pg_freespacemap--1.1--1.2.sql
@@ -0,0 +1,7 @@
+/* contrib/pg_freespacemap/pg_freespacemap--1.1--1.2.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION pg_freespacemap UPDATE TO '1.2'" to load this file. \quit
+
+GRANT EXECUTE ON FUNCTION  pg_freespace(regclass, bigint) TO pg_stat_scan_tables;
+GRANT EXECUTE ON FUNCTION  pg_freespace(regclass) TO pg_stat_scan_tables;
diff --git a/contrib/pg_freespacemap/pg_freespacemap--1.1.sql b/contrib/pg_freespacemap/pg_freespacemap--1.1.sql
new file mode 100644
index 0000000..e1b8242
--- /dev/null
+++ b/contrib/pg_freespacemap/pg_freespacemap--1.1.sql
@@ -0,0 +1,25 @@
+/* contrib/pg_freespacemap/pg_freespacemap--1.1.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION pg_freespacemap" to load this file. \quit
+
+-- Register the C function.
+CREATE FUNCTION pg_freespace(regclass, bigint)
+RETURNS int2
+AS 'MODULE_PATHNAME', 'pg_freespace'
+LANGUAGE C STRICT PARALLEL SAFE;
+
+-- pg_freespace shows the recorded space avail at each block in a relation
+CREATE FUNCTION
+  pg_freespace(rel regclass, blkno OUT bigint, avail OUT int2)
+RETURNS SETOF RECORD
+AS $$
+  SELECT blkno, pg_freespace($1, blkno) AS avail
+  FROM generate_series(0, pg_relation_size($1) / current_setting('block_size')::bigint - 1) AS blkno;
+$$
+LANGUAGE SQL PARALLEL SAFE;
+
+
+-- Don't want these to be available to public.
+REVOKE ALL ON FUNCTION pg_freespace(regclass, bigint) FROM PUBLIC;
+REVOKE ALL ON FUNCTION pg_freespace(regclass) FROM PUBLIC;
diff --git a/contrib/pg_freespacemap/pg_freespacemap.c b/contrib/pg_freespacemap/pg_freespacemap.c
new file mode 100644
index 0000000..b82cab2
--- /dev/null
+++ b/contrib/pg_freespacemap/pg_freespacemap.c
@@ -0,0 +1,42 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_freespacemap.c
+ *	  display contents of a free space map
+ *
+ *	  contrib/pg_freespacemap/pg_freespacemap.c
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/relation.h"
+#include "funcapi.h"
+#include "storage/freespace.h"
+
+PG_MODULE_MAGIC;
+
+/*
+ * Returns the amount of free space on a given page, according to the
+ * free space map.
+ */
+PG_FUNCTION_INFO_V1(pg_freespace);
+
+Datum
+pg_freespace(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	int64		blkno = PG_GETARG_INT64(1);
+	int16		freespace;
+	Relation	rel;
+
+	rel = relation_open(relid, AccessShareLock);
+
+	if (blkno < 0 || blkno > MaxBlockNumber)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid block number")));
+
+	freespace = GetRecordedFreeSpace(rel, blkno);
+
+	relation_close(rel, AccessShareLock);
+	PG_RETURN_INT16(freespace);
+}
diff --git a/contrib/pg_freespacemap/pg_freespacemap.control b/contrib/pg_freespacemap/pg_freespacemap.control
new file mode 100644
index 0000000..ac8fc50
--- /dev/null
+++ b/contrib/pg_freespacemap/pg_freespacemap.control
@@ -0,0 +1,5 @@
+# pg_freespacemap extension
+comment = 'examine the free space map (FSM)'
+default_version = '1.2'
+module_pathname = '$libdir/pg_freespacemap'
+relocatable = true