Add visibility map information to pg_freespace.

Helle,

I've added visibility map information to pg_freespace for my
utility.

This looks like this,

postgres=# select * from pg_freespace('t'::regclass);blkno | avail | all_visible 
-------+-------+-------------    0 |  7424 | t    1 |  7424 | t    2 |  7424 | t    3 |  7424 | t    4 |  7424 | t    5
| 7424 | t    6 |  7424 | t    7 |  7424 | t
 
...

What do you think about this?


regards,

-- 
Kyotaro Horiguchi
NTT Open Source Software Center
diff --git a/contrib/pg_freespacemap/pg_freespacemap--1.0.sql b/contrib/pg_freespacemap/pg_freespacemap--1.0.sql
index 2adb52a..e38b466 100644
--- a/contrib/pg_freespacemap/pg_freespacemap--1.0.sql
+++ b/contrib/pg_freespacemap/pg_freespacemap--1.0.sql
@@ -9,12 +9,17 @@ RETURNS int2AS 'MODULE_PATHNAME', 'pg_freespace'LANGUAGE C STRICT;
+CREATE FUNCTION pg_is_all_visible(regclass, bigint)
+RETURNS bool
+AS 'MODULE_PATHNAME', 'pg_is_all_visible'
+LANGUAGE C STRICT;
+-- pg_freespace shows the recorded space avail at each block in a relationCREATE FUNCTION
-  pg_freespace(rel regclass, blkno OUT bigint, avail OUT int2)
+  pg_freespace(rel regclass, blkno OUT bigint, avail OUT int2, all_visible OUT bool)RETURNS SETOF RECORDAS $$
-  SELECT blkno, pg_freespace($1, blkno) AS avail
+  SELECT blkno, pg_freespace($1, blkno) AS avail, pg_is_all_visible($1, blkno) AS all_visible  FROM generate_series(0,
pg_relation_size($1)/ current_setting('block_size')::bigint - 1) AS blkno;$$LANGUAGE SQL;
 
diff --git a/contrib/pg_freespacemap/pg_freespacemap.c b/contrib/pg_freespacemap/pg_freespacemap.c
index f6f7d2e..de4eff7 100644
--- a/contrib/pg_freespacemap/pg_freespacemap.c
+++ b/contrib/pg_freespacemap/pg_freespacemap.c
@@ -10,17 +10,20 @@#include "funcapi.h"#include "storage/freespace.h"
+#include "access/visibilitymap.h"PG_MODULE_MAGIC;Datum        pg_freespace(PG_FUNCTION_ARGS);
+Datum        pg_is_all_visible(PG_FUNCTION_ARGS);/* * Returns the amount of free space on a given page, according to
the* free space map. */PG_FUNCTION_INFO_V1(pg_freespace);
 
+PG_FUNCTION_INFO_V1(pg_is_all_visible);Datumpg_freespace(PG_FUNCTION_ARGS)
@@ -38,7 +41,32 @@ pg_freespace(PG_FUNCTION_ARGS)                 errmsg("invalid block number")));    freespace =
GetRecordedFreeSpace(rel,blkno);
 
-    relation_close(rel, AccessShareLock);    PG_RETURN_INT16(freespace);}
+
+Datum
+pg_is_all_visible(PG_FUNCTION_ARGS)
+{
+    Oid            relid = PG_GETARG_OID(0);
+    int64        blkno = PG_GETARG_INT64(1);
+    Buffer      vmbuffer = InvalidBuffer;
+    int            all_visible;
+    Relation    rel;
+
+    rel = relation_open(relid, AccessShareLock);
+
+    if (blkno < 0 || blkno > MaxBlockNumber)
+        ereport(ERROR,
+                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+                 errmsg("invalid block number")));
+
+    all_visible = visibilitymap_test(rel, blkno, &vmbuffer);
+    if (vmbuffer != InvalidBuffer)
+    {
+        ReleaseBuffer(vmbuffer);
+        vmbuffer = InvalidBuffer;
+    }
+    relation_close(rel, AccessShareLock);
+    PG_RETURN_BOOL(all_visible);
+}
diff --git a/contrib/pg_freespacemap/pg_freespacemap.control b/contrib/pg_freespacemap/pg_freespacemap.control
index 34b695f..395350a 100644
--- a/contrib/pg_freespacemap/pg_freespacemap.control
+++ b/contrib/pg_freespacemap/pg_freespacemap.control
@@ -1,5 +1,5 @@# pg_freespacemap extension
-comment = 'examine the free space map (FSM)'
+comment = 'examine the free space map (FSM) and visibility map (VM)'default_version = '1.0'module_pathname =
'$libdir/pg_freespacemap'relocatable= true