mirror of
https://git.postgresql.org/git/postgresql.git
synced 2025-01-30 19:00:29 +08:00
Add pg_visibility contrib module.
This lets you examine the visibility map as well as page-level visibility information. I initially wrote it as a debugging aid, but was encouraged to polish it for commit. Patch by me, reviewed by Masahiko Sawada. Discussion: 56D77803.6080503@BlueTreble.com
This commit is contained in:
Robert Haas
parent
6f56b41ac0
commit
ba0a198fb1
@ -37,6 +37,7 @@ SUBDIRS = \
|
|||||||
pgcrypto \
|
pgcrypto \
|
||||||
pgrowlocks \
|
pgrowlocks \
|
||||||
pgstattuple \
|
pgstattuple \
|
||||||
|
pg_visibility \
|
||||||
postgres_fdw \
|
postgres_fdw \
|
||||||
seg \
|
seg \
|
||||||
spi \
|
spi \
|
||||||
|
|||||||
19
contrib/pg_visibility/Makefile
Normal file
19
contrib/pg_visibility/Makefile
Normal file
@ -0,0 +1,19 @@
|
|||||||
|
# contrib/pg_visibility/Makefile
|
||||||
|
|
||||||
|
MODULE_big = pg_visibility
|
||||||
|
OBJS = pg_visibility.o $(WIN32RES)
|
||||||
|
|
||||||
|
EXTENSION = pg_visibility
|
||||||
|
DATA = pg_visibility--1.0.sql
|
||||||
|
PGFILEDESC = "pg_visibility - page visibility information"
|
||||||
|
|
||||||
|
ifdef USE_PGXS
|
||||||
|
PG_CONFIG = pg_config
|
||||||
|
PGXS := $(shell $(PG_CONFIG) --pgxs)
|
||||||
|
include $(PGXS)
|
||||||
|
else
|
||||||
|
subdir = contrib/pg_visibility
|
||||||
|
top_builddir = ../..
|
||||||
|
include $(top_builddir)/src/Makefile.global
|
||||||
|
include $(top_srcdir)/contrib/contrib-global.mk
|
||||||
|
endif
|
||||||
52
contrib/pg_visibility/pg_visibility--1.0.sql
Normal file
52
contrib/pg_visibility/pg_visibility--1.0.sql
Normal file
@ -0,0 +1,52 @@
|
|||||||
|
/* contrib/pg_visibility/pg_visibility--1.0.sql */
|
||||||
|
|
||||||
|
-- complain if script is sourced in psql, rather than via CREATE EXTENSION
|
||||||
|
\echo Use "CREATE EXTENSION pg_visibility" to load this file. \quit
|
||||||
|
|
||||||
|
-- Show visibility map information.
|
||||||
|
CREATE FUNCTION pg_visibility_map(regclass, blkno bigint,
|
||||||
|
all_visible OUT boolean,
|
||||||
|
all_frozen OUT boolean)
|
||||||
|
RETURNS record
|
||||||
|
AS 'MODULE_PATHNAME', 'pg_visibility_map'
|
||||||
|
LANGUAGE C STRICT;
|
||||||
|
|
||||||
|
-- Show visibility map and page-level visibility information.
|
||||||
|
CREATE FUNCTION pg_visibility(regclass, blkno bigint,
|
||||||
|
all_visible OUT boolean,
|
||||||
|
all_frozen OUT boolean,
|
||||||
|
pd_all_visible OUT boolean)
|
||||||
|
RETURNS record
|
||||||
|
AS 'MODULE_PATHNAME', 'pg_visibility'
|
||||||
|
LANGUAGE C STRICT;
|
||||||
|
|
||||||
|
-- Show visibility map information for each block in a relation.
|
||||||
|
CREATE FUNCTION pg_visibility_map(regclass, blkno OUT bigint,
|
||||||
|
all_visible OUT boolean,
|
||||||
|
all_frozen OUT boolean)
|
||||||
|
RETURNS SETOF record
|
||||||
|
AS 'MODULE_PATHNAME', 'pg_visibility_map_rel'
|
||||||
|
LANGUAGE C STRICT;
|
||||||
|
|
||||||
|
-- Show visibility map and page-level visibility information for each block.
|
||||||
|
CREATE FUNCTION pg_visibility(regclass, blkno OUT bigint,
|
||||||
|
all_visible OUT boolean,
|
||||||
|
all_frozen OUT boolean,
|
||||||
|
pd_all_visible OUT boolean)
|
||||||
|
RETURNS SETOF record
|
||||||
|
AS 'MODULE_PATHNAME', 'pg_visibility_rel'
|
||||||
|
LANGUAGE C STRICT;
|
||||||
|
|
||||||
|
-- Show summary of visibility map bits for a relation.
|
||||||
|
CREATE FUNCTION pg_visibility_map_summary(regclass,
|
||||||
|
OUT all_visible bigint, OUT all_frozen bigint)
|
||||||
|
RETURNS record
|
||||||
|
AS 'MODULE_PATHNAME', 'pg_visibility_map_summary'
|
||||||
|
LANGUAGE C STRICT;
|
||||||
|
|
||||||
|
-- Don't want these to be available to public.
|
||||||
|
REVOKE ALL ON FUNCTION pg_visibility_map(regclass, bigint) FROM PUBLIC;
|
||||||
|
REVOKE ALL ON FUNCTION pg_visibility(regclass, bigint) FROM PUBLIC;
|
||||||
|
REVOKE ALL ON FUNCTION pg_visibility_map(regclass) FROM PUBLIC;
|
||||||
|
REVOKE ALL ON FUNCTION pg_visibility(regclass) FROM PUBLIC;
|
||||||
|
REVOKE ALL ON FUNCTION pg_visibility_map_summary(regclass) FROM PUBLIC;
|
||||||
350
contrib/pg_visibility/pg_visibility.c
Normal file
350
contrib/pg_visibility/pg_visibility.c
Normal file
@ -0,0 +1,350 @@
|
|||||||
|
/*-------------------------------------------------------------------------
|
||||||
|
*
|
||||||
|
* pg_visibility.c
|
||||||
|
* display visibility map information and page-level visibility bits
|
||||||
|
*
|
||||||
|
* contrib/pg_visibility/pg_visibility.c
|
||||||
|
*-------------------------------------------------------------------------
|
||||||
|
*/
|
||||||
|
#include "postgres.h"
|
||||||
|
|
||||||
|
#include "access/htup_details.h"
|
||||||
|
#include "access/visibilitymap.h"
|
||||||
|
#include "catalog/pg_type.h"
|
||||||
|
#include "funcapi.h"
|
||||||
|
#include "miscadmin.h"
|
||||||
|
#include "storage/bufmgr.h"
|
||||||
|
#include "utils/rel.h"
|
||||||
|
|
||||||
|
PG_MODULE_MAGIC;
|
||||||
|
|
||||||
|
typedef struct vbits
|
||||||
|
{
|
||||||
|
BlockNumber next;
|
||||||
|
BlockNumber count;
|
||||||
|
uint8 bits[FLEXIBLE_ARRAY_MEMBER];
|
||||||
|
} vbits;
|
||||||
|
|
||||||
|
PG_FUNCTION_INFO_V1(pg_visibility_map);
|
||||||
|
PG_FUNCTION_INFO_V1(pg_visibility_map_rel);
|
||||||
|
PG_FUNCTION_INFO_V1(pg_visibility);
|
||||||
|
PG_FUNCTION_INFO_V1(pg_visibility_rel);
|
||||||
|
PG_FUNCTION_INFO_V1(pg_visibility_map_summary);
|
||||||
|
|
||||||
|
static TupleDesc pg_visibility_tupdesc(bool include_blkno, bool include_pd);
|
||||||
|
static vbits *collect_visibility_data(Oid relid, bool include_pd);
|
||||||
|
|
||||||
|
/*
|
||||||
|
* Visibility map information for a single block of a relation.
|
||||||
|
*/
|
||||||
|
Datum
|
||||||
|
pg_visibility_map(PG_FUNCTION_ARGS)
|
||||||
|
{
|
||||||
|
Oid relid = PG_GETARG_OID(0);
|
||||||
|
int64 blkno = PG_GETARG_INT64(1);
|
||||||
|
int32 mapbits;
|
||||||
|
Relation rel;
|
||||||
|
Buffer vmbuffer = InvalidBuffer;
|
||||||
|
TupleDesc tupdesc;
|
||||||
|
Datum values[2];
|
||||||
|
bool nulls[2];
|
||||||
|
|
||||||
|
rel = relation_open(relid, AccessShareLock);
|
||||||
|
|
||||||
|
if (blkno < 0 || blkno > MaxBlockNumber)
|
||||||
|
ereport(ERROR,
|
||||||
|
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
|
||||||
|
errmsg("invalid block number")));
|
||||||
|
|
||||||
|
tupdesc = pg_visibility_tupdesc(false, false);
|
||||||
|
MemSet(nulls, 0, sizeof(nulls));
|
||||||
|
|
||||||
|
mapbits = (int32) visibilitymap_get_status(rel, blkno, &vmbuffer);
|
||||||
|
if (vmbuffer != InvalidBuffer)
|
||||||
|
ReleaseBuffer(vmbuffer);
|
||||||
|
values[0] = BoolGetDatum((mapbits & VISIBILITYMAP_ALL_VISIBLE) != 0);
|
||||||
|
values[1] = BoolGetDatum((mapbits & VISIBILITYMAP_ALL_FROZEN) != 0);
|
||||||
|
|
||||||
|
relation_close(rel, AccessShareLock);
|
||||||
|
|
||||||
|
PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
|
||||||
|
}
|
||||||
|
|
||||||
|
/*
|
||||||
|
* Visibility map information for a single block of a relation, plus the
|
||||||
|
* page-level information for the same block.
|
||||||
|
*/
|
||||||
|
Datum
|
||||||
|
pg_visibility(PG_FUNCTION_ARGS)
|
||||||
|
{
|
||||||
|
Oid relid = PG_GETARG_OID(0);
|
||||||
|
int64 blkno = PG_GETARG_INT64(1);
|
||||||
|
int32 mapbits;
|
||||||
|
Relation rel;
|
||||||
|
Buffer vmbuffer = InvalidBuffer;
|
||||||
|
Buffer buffer;
|
||||||
|
Page page;
|
||||||
|
TupleDesc tupdesc;
|
||||||
|
Datum values[3];
|
||||||
|
bool nulls[3];
|
||||||
|
|
||||||
|
rel = relation_open(relid, AccessShareLock);
|
||||||
|
|
||||||
|
if (blkno < 0 || blkno > MaxBlockNumber)
|
||||||
|
ereport(ERROR,
|
||||||
|
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
|
||||||
|
errmsg("invalid block number")));
|
||||||
|
|
||||||
|
tupdesc = pg_visibility_tupdesc(false, true);
|
||||||
|
MemSet(nulls, 0, sizeof(nulls));
|
||||||
|
|
||||||
|
mapbits = (int32) visibilitymap_get_status(rel, blkno, &vmbuffer);
|
||||||
|
if (vmbuffer != InvalidBuffer)
|
||||||
|
ReleaseBuffer(vmbuffer);
|
||||||
|
values[0] = BoolGetDatum((mapbits & VISIBILITYMAP_ALL_VISIBLE) != 0);
|
||||||
|
values[1] = BoolGetDatum((mapbits & VISIBILITYMAP_ALL_FROZEN) != 0);
|
||||||
|
|
||||||
|
buffer = ReadBuffer(rel, blkno);
|
||||||
|
LockBuffer(buffer, BUFFER_LOCK_SHARE);
|
||||||
|
|
||||||
|
page = BufferGetPage(buffer);
|
||||||
|
values[2] = BoolGetDatum(PageIsAllVisible(page));
|
||||||
|
|
||||||
|
UnlockReleaseBuffer(buffer);
|
||||||
|
|
||||||
|
relation_close(rel, AccessShareLock);
|
||||||
|
|
||||||
|
PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
|
||||||
|
}
|
||||||
|
|
||||||
|
/*
|
||||||
|
* Visibility map information for every block in a relation.
|
||||||
|
*/
|
||||||
|
Datum
|
||||||
|
pg_visibility_map_rel(PG_FUNCTION_ARGS)
|
||||||
|
{
|
||||||
|
FuncCallContext *funcctx;
|
||||||
|
vbits *info;
|
||||||
|
|
||||||
|
if (SRF_IS_FIRSTCALL())
|
||||||
|
{
|
||||||
|
Oid relid = PG_GETARG_OID(0);
|
||||||
|
MemoryContext oldcontext;
|
||||||
|
|
||||||
|
funcctx = SRF_FIRSTCALL_INIT();
|
||||||
|
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
|
||||||
|
funcctx->tuple_desc = pg_visibility_tupdesc(true, false);
|
||||||
|
funcctx->user_fctx = collect_visibility_data(relid, false);
|
||||||
|
MemoryContextSwitchTo(oldcontext);
|
||||||
|
}
|
||||||
|
|
||||||
|
funcctx = SRF_PERCALL_SETUP();
|
||||||
|
info = (vbits *) funcctx->user_fctx;
|
||||||
|
|
||||||
|
if (info->next < info->count)
|
||||||
|
{
|
||||||
|
Datum values[3];
|
||||||
|
bool nulls[3];
|
||||||
|
HeapTuple tuple;
|
||||||
|
|
||||||
|
MemSet(nulls, 0, sizeof(nulls));
|
||||||
|
values[0] = Int64GetDatum(info->next);
|
||||||
|
values[1] = BoolGetDatum((info->bits[info->next] & (1 << 0)) != 0);
|
||||||
|
values[2] = BoolGetDatum((info->bits[info->next] & (1 << 1)) != 0);
|
||||||
|
info->next++;
|
||||||
|
|
||||||
|
tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
|
||||||
|
SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
|
||||||
|
}
|
||||||
|
|
||||||
|
SRF_RETURN_DONE(funcctx);
|
||||||
|
}
|
||||||
|
|
||||||
|
/*
|
||||||
|
* Visibility map information for every block in a relation, plus the page
|
||||||
|
* level information for each block.
|
||||||
|
*/
|
||||||
|
Datum
|
||||||
|
pg_visibility_rel(PG_FUNCTION_ARGS)
|
||||||
|
{
|
||||||
|
FuncCallContext *funcctx;
|
||||||
|
vbits *info;
|
||||||
|
|
||||||
|
if (SRF_IS_FIRSTCALL())
|
||||||
|
{
|
||||||
|
Oid relid = PG_GETARG_OID(0);
|
||||||
|
MemoryContext oldcontext;
|
||||||
|
|
||||||
|
funcctx = SRF_FIRSTCALL_INIT();
|
||||||
|
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
|
||||||
|
funcctx->tuple_desc = pg_visibility_tupdesc(true, true);
|
||||||
|
funcctx->user_fctx = collect_visibility_data(relid, true);
|
||||||
|
MemoryContextSwitchTo(oldcontext);
|
||||||
|
}
|
||||||
|
|
||||||
|
funcctx = SRF_PERCALL_SETUP();
|
||||||
|
info = (vbits *) funcctx->user_fctx;
|
||||||
|
|
||||||
|
if (info->next < info->count)
|
||||||
|
{
|
||||||
|
Datum values[4];
|
||||||
|
bool nulls[4];
|
||||||
|
HeapTuple tuple;
|
||||||
|
|
||||||
|
MemSet(nulls, 0, sizeof(nulls));
|
||||||
|
values[0] = Int64GetDatum(info->next);
|
||||||
|
values[1] = BoolGetDatum((info->bits[info->next] & (1 << 0)) != 0);
|
||||||
|
values[2] = BoolGetDatum((info->bits[info->next] & (1 << 1)) != 0);
|
||||||
|
values[3] = BoolGetDatum((info->bits[info->next] & (1 << 2)) != 0);
|
||||||
|
info->next++;
|
||||||
|
|
||||||
|
tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
|
||||||
|
SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
|
||||||
|
}
|
||||||
|
|
||||||
|
SRF_RETURN_DONE(funcctx);
|
||||||
|
}
|
||||||
|
|
||||||
|
/*
|
||||||
|
* Count the number of all-visible and all-frozen pages in the visibility
|
||||||
|
* map for a particular relation.
|
||||||
|
*/
|
||||||
|
Datum
|
||||||
|
pg_visibility_map_summary(PG_FUNCTION_ARGS)
|
||||||
|
{
|
||||||
|
Oid relid = PG_GETARG_OID(0);
|
||||||
|
Relation rel;
|
||||||
|
BlockNumber nblocks;
|
||||||
|
BlockNumber blkno;
|
||||||
|
Buffer vmbuffer = InvalidBuffer;
|
||||||
|
int64 all_visible = 0;
|
||||||
|
int64 all_frozen = 0;
|
||||||
|
TupleDesc tupdesc;
|
||||||
|
Datum values[2];
|
||||||
|
bool nulls[2];
|
||||||
|
|
||||||
|
rel = relation_open(relid, AccessShareLock);
|
||||||
|
nblocks = RelationGetNumberOfBlocks(rel);
|
||||||
|
|
||||||
|
for (blkno = 0; blkno < nblocks; ++blkno)
|
||||||
|
{
|
||||||
|
int32 mapbits;
|
||||||
|
|
||||||
|
/* Make sure we are interruptible. */
|
||||||
|
CHECK_FOR_INTERRUPTS();
|
||||||
|
|
||||||
|
/* Get map info. */
|
||||||
|
mapbits = (int32) visibilitymap_get_status(rel, blkno, &vmbuffer);
|
||||||
|
if ((mapbits & VISIBILITYMAP_ALL_VISIBLE) != 0)
|
||||||
|
++all_visible;
|
||||||
|
if ((mapbits & VISIBILITYMAP_ALL_FROZEN) != 0)
|
||||||
|
++all_frozen;
|
||||||
|
}
|
||||||
|
|
||||||
|
/* Clean up. */
|
||||||
|
if (vmbuffer != InvalidBuffer)
|
||||||
|
ReleaseBuffer(vmbuffer);
|
||||||
|
relation_close(rel, AccessShareLock);
|
||||||
|
|
||||||
|
tupdesc = CreateTemplateTupleDesc(2, false);
|
||||||
|
TupleDescInitEntry(tupdesc, (AttrNumber) 1, "all_visible", INT8OID, -1, 0);
|
||||||
|
TupleDescInitEntry(tupdesc, (AttrNumber) 2, "all_frozen", INT8OID, -1, 0);
|
||||||
|
tupdesc = BlessTupleDesc(tupdesc);
|
||||||
|
|
||||||
|
MemSet(nulls, 0, sizeof(nulls));
|
||||||
|
values[0] = Int64GetDatum(all_visible);
|
||||||
|
values[1] = Int64GetDatum(all_frozen);
|
||||||
|
|
||||||
|
PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
|
||||||
|
}
|
||||||
|
|
||||||
|
/*
|
||||||
|
* Helper function to construct whichever TupleDesc we need for a particular
|
||||||
|
* call.
|
||||||
|
*/
|
||||||
|
static TupleDesc
|
||||||
|
pg_visibility_tupdesc(bool include_blkno, bool include_pd)
|
||||||
|
{
|
||||||
|
TupleDesc tupdesc;
|
||||||
|
AttrNumber maxattr = 2;
|
||||||
|
AttrNumber a = 0;
|
||||||
|
|
||||||
|
if (include_blkno)
|
||||||
|
++maxattr;
|
||||||
|
if (include_pd)
|
||||||
|
++maxattr;
|
||||||
|
tupdesc = CreateTemplateTupleDesc(maxattr, false);
|
||||||
|
if (include_blkno)
|
||||||
|
TupleDescInitEntry(tupdesc, ++a, "blkno", INT8OID, -1, 0);
|
||||||
|
TupleDescInitEntry(tupdesc, ++a, "all_visible", BOOLOID, -1, 0);
|
||||||
|
TupleDescInitEntry(tupdesc, ++a, "all_frozen", BOOLOID, -1, 0);
|
||||||
|
if (include_pd)
|
||||||
|
TupleDescInitEntry(tupdesc, ++a, "pd_all_visible", BOOLOID, -1, 0);
|
||||||
|
Assert(a == maxattr);
|
||||||
|
|
||||||
|
return BlessTupleDesc(tupdesc);
|
||||||
|
}
|
||||||
|
|
||||||
|
/*
|
||||||
|
* Collect visibility data about a relation.
|
||||||
|
*/
|
||||||
|
static vbits *
|
||||||
|
collect_visibility_data(Oid relid, bool include_pd)
|
||||||
|
{
|
||||||
|
Relation rel;
|
||||||
|
BlockNumber nblocks;
|
||||||
|
vbits *info;
|
||||||
|
BlockNumber blkno;
|
||||||
|
Buffer vmbuffer = InvalidBuffer;
|
||||||
|
BufferAccessStrategy bstrategy = GetAccessStrategy(BAS_BULKREAD);
|
||||||
|
|
||||||
|
rel = relation_open(relid, AccessShareLock);
|
||||||
|
|
||||||
|
nblocks = RelationGetNumberOfBlocks(rel);
|
||||||
|
info = palloc0(offsetof(vbits, bits) + nblocks);
|
||||||
|
info->next = 0;
|
||||||
|
info->count = nblocks;
|
||||||
|
|
||||||
|
for (blkno = 0; blkno < nblocks; ++blkno)
|
||||||
|
{
|
||||||
|
int32 mapbits;
|
||||||
|
|
||||||
|
/* Make sure we are interruptible. */
|
||||||
|
CHECK_FOR_INTERRUPTS();
|
||||||
|
|
||||||
|
/* Get map info. */
|
||||||
|
mapbits = (int32) visibilitymap_get_status(rel, blkno, &vmbuffer);
|
||||||
|
if ((mapbits & VISIBILITYMAP_ALL_VISIBLE) != 0)
|
||||||
|
info->bits[blkno] |= (1 << 0);
|
||||||
|
if ((mapbits & VISIBILITYMAP_ALL_FROZEN) != 0)
|
||||||
|
info->bits[blkno] |= (1 << 1);
|
||||||
|
|
||||||
|
/*
|
||||||
|
* Page-level data requires reading every block, so only get it if
|
||||||
|
* the caller needs it. Use a buffer access strategy, too, to prevent
|
||||||
|
* cache-trashing.
|
||||||
|
*/
|
||||||
|
if (include_pd)
|
||||||
|
{
|
||||||
|
Buffer buffer;
|
||||||
|
Page page;
|
||||||
|
|
||||||
|
buffer = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL,
|
||||||
|
bstrategy);
|
||||||
|
LockBuffer(buffer, BUFFER_LOCK_SHARE);
|
||||||
|
|
||||||
|
page = BufferGetPage(buffer);
|
||||||
|
if (PageIsAllVisible(page))
|
||||||
|
info->bits[blkno] |= (1 << 2);
|
||||||
|
|
||||||
|
UnlockReleaseBuffer(buffer);
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
/* Clean up. */
|
||||||
|
if (vmbuffer != InvalidBuffer)
|
||||||
|
ReleaseBuffer(vmbuffer);
|
||||||
|
relation_close(rel, AccessShareLock);
|
||||||
|
|
||||||
|
return info;
|
||||||
|
}
|
||||||
5
contrib/pg_visibility/pg_visibility.control
Normal file
5
contrib/pg_visibility/pg_visibility.control
Normal file
@ -0,0 +1,5 @@
|
|||||||
|
# pg_visibility extension
|
||||||
|
comment = 'examine the visibility map (VM) and page-level visibility info'
|
||||||
|
default_version = '1.0'
|
||||||
|
module_pathname = '$libdir/pg_visibility'
|
||||||
|
relocatable = true
|
||||||
@ -132,6 +132,7 @@ CREATE EXTENSION <replaceable>module_name</> FROM unpackaged;
|
|||||||
&pgstatstatements;
|
&pgstatstatements;
|
||||||
&pgstattuple;
|
&pgstattuple;
|
||||||
&pgtrgm;
|
&pgtrgm;
|
||||||
|
&pgvisibility;
|
||||||
&postgres-fdw;
|
&postgres-fdw;
|
||||||
&seg;
|
&seg;
|
||||||
&sepgsql;
|
&sepgsql;
|
||||||
|
|||||||
@ -136,6 +136,7 @@
|
|||||||
<!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
|
<!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
|
||||||
<!ENTITY pgstattuple SYSTEM "pgstattuple.sgml">
|
<!ENTITY pgstattuple SYSTEM "pgstattuple.sgml">
|
||||||
<!ENTITY pgtrgm SYSTEM "pgtrgm.sgml">
|
<!ENTITY pgtrgm SYSTEM "pgtrgm.sgml">
|
||||||
|
<!ENTITY pgvisibility SYSTEM "pgvisibility.sgml">
|
||||||
<!ENTITY postgres-fdw SYSTEM "postgres-fdw.sgml">
|
<!ENTITY postgres-fdw SYSTEM "postgres-fdw.sgml">
|
||||||
<!ENTITY seg SYSTEM "seg.sgml">
|
<!ENTITY seg SYSTEM "seg.sgml">
|
||||||
<!ENTITY contrib-spi SYSTEM "contrib-spi.sgml">
|
<!ENTITY contrib-spi SYSTEM "contrib-spi.sgml">
|
||||||
|
|||||||
110
doc/src/sgml/pgvisibility.sgml
Normal file
110
doc/src/sgml/pgvisibility.sgml
Normal file
@ -0,0 +1,110 @@
|
|||||||
|
<!-- doc/src/sgml/pgvisibility.sgml -->
|
||||||
|
|
||||||
|
<sect1 id="pgvisibility" xreflabel="pg_visibility">
|
||||||
|
<title>pg_visibility</title>
|
||||||
|
|
||||||
|
<indexterm zone="pgvisibility">
|
||||||
|
<primary>pg_visibility</primary>
|
||||||
|
</indexterm>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The <filename>pg_visibility</> module provides a means for examining the
|
||||||
|
visibility map (VM) and page-level visibility information.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
These routines return information about three different bits. The
|
||||||
|
all-visible bit in the visibility map indicates that every tuple on
|
||||||
|
a given page of a relation is visible to every current transaction. The
|
||||||
|
all-frozen bit in the visibility map indicates that every tuple on the
|
||||||
|
page is frozen; that is, no future vacuum will need to modify the page
|
||||||
|
until such time as a tuple is inserted, updated, deleted, or locked on
|
||||||
|
that page. The page-level <literal>PD_ALL_VISIBLE</literal> bit has the
|
||||||
|
same meaning as the all-visible bit in the visibility map, but is stored
|
||||||
|
within the data page itself rather than a separate data tructure. These
|
||||||
|
will normally agree, but the page-level bit can sometimes be set while the
|
||||||
|
visibility map bit is clear after a crash recovery; or they can disagree
|
||||||
|
because of a change which occurs after <literal>pg_visibility</> examines
|
||||||
|
the visibility map and before it examines the data page.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Functions which display information about <literal>PG_ALL_VISIBLE</>
|
||||||
|
are much more costly than those which only consult the visibility map,
|
||||||
|
because they must read the relation's data blocks rather than only the
|
||||||
|
(much smaller) visibility map.
|
||||||
|
</para>
|
||||||
|
|
||||||
|
<sect2>
|
||||||
|
<title>Functions</title>
|
||||||
|
|
||||||
|
<variablelist>
|
||||||
|
<varlistentry>
|
||||||
|
<term><function>pg_visibility_map(regclass, blkno bigint, all_visible OUT boolean, all_frozen OUT boolean) returns record</function></term>
|
||||||
|
<listitem>
|
||||||
|
<para>
|
||||||
|
Returns the all-visible and all-frozen bits in the visibility map for
|
||||||
|
the given block of the given relation.
|
||||||
|
</para>
|
||||||
|
</listitem>
|
||||||
|
</varlistentry>
|
||||||
|
|
||||||
|
<varlistentry>
|
||||||
|
<term><function>pg_visibility(regclass, blkno bigint, all_visible OUT boolean, all_frozen OUT boolean, pd_all_visible OUT boolean) returns record</function></term>
|
||||||
|
<listitem>
|
||||||
|
<para>
|
||||||
|
Returns the all-visible and all-frozen bits in the visibility map for
|
||||||
|
the given block of the given relation, plus the
|
||||||
|
<literal>PD_ALL_VISIBILE</> bit for that block.
|
||||||
|
</para>
|
||||||
|
</listitem>
|
||||||
|
</varlistentry>
|
||||||
|
|
||||||
|
<varlistentry>
|
||||||
|
<term><function>pg_visibility_map(regclass, blkno OUT bigint, all_visible OUT boolean, all_frozen OUT boolean) returns record</function></term>
|
||||||
|
<listitem>
|
||||||
|
<para>
|
||||||
|
Returns the all-visible and all-frozen bits in the visibility map for
|
||||||
|
each block the given relation.
|
||||||
|
</para>
|
||||||
|
</listitem>
|
||||||
|
</varlistentry>
|
||||||
|
|
||||||
|
<varlistentry>
|
||||||
|
<term><function>pg_visibility(regclass, blkno OUT bigint, all_visible OUT boolean, all_frozen OUT boolean, pd_all_visible OUT boolean) returns record</function></term>
|
||||||
|
|
||||||
|
<listitem>
|
||||||
|
<para>
|
||||||
|
Returns the all-visible and all-frozen bits in the visibility map for
|
||||||
|
each block the given relation, plus the <literal>PD_ALL_VISIBLE</>
|
||||||
|
bit for each block.
|
||||||
|
</para>
|
||||||
|
</listitem>
|
||||||
|
</varlistentry>
|
||||||
|
|
||||||
|
<varlistentry>
|
||||||
|
<term><function>pg_visibility_map_summary(regclass, all_visible OUT bigint, all_frozen OUT bigint) returns record</function></term>
|
||||||
|
|
||||||
|
<listitem>
|
||||||
|
<para>
|
||||||
|
Returns the number of all-visible pages and the number of all-frozen
|
||||||
|
pages in the relation according to the visibility map.
|
||||||
|
</para>
|
||||||
|
</listitem>
|
||||||
|
</varlistentry>
|
||||||
|
</variablelist>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
By default, these functions are not publicly executable.
|
||||||
|
</para>
|
||||||
|
</sect2>
|
||||||
|
|
||||||
|
<sect2>
|
||||||
|
<title>Author</title>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Robert Haas <email>rhaas@postgresql.org</email>
|
||||||
|
</para>
|
||||||
|
</sect2>
|
||||||
|
|
||||||
|
</sect1>
|
||||||
@ -648,6 +648,11 @@ might not be true. Visibility map bits are only set by vacuum, but are
|
|||||||
cleared by any data-modifying operations on a page.
|
cleared by any data-modifying operations on a page.
|
||||||
</para>
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
The <xref linkend="pgvisibility"> module can be used to examine the
|
||||||
|
information stored in the visibility map.
|
||||||
|
</para>
|
||||||
|
|
||||||
</sect1>
|
</sect1>
|
||||||
|
|
||||||
<sect1 id="storage-init">
|
<sect1 id="storage-init">
|
||||||
|
|||||||
Loading…
Reference in New Issue
Block a user