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Add contrib/pg_freespacemap to display free space map information.
Mark Kirkwood
1 parent 6c0d4aa commit d5dd3d4

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‎contrib/Makefile

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# $PostgreSQL: pgsql/contrib/Makefile,v 1.61 2005/09/01 22:02:44 tgl Exp $
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# $PostgreSQL: pgsql/contrib/Makefile,v 1.62 2006/02/12 03:55:52 momjian Exp $
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subdir = contrib
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top_builddir = ..
@@ -21,6 +21,7 @@ WANTED_DIRS = \
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ltree \
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oid2name \
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pg_buffercache \
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pg_freespacemap \
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pg_trgm \
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pgbench \
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pgcrypto \

‎contrib/README

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@@ -106,6 +106,10 @@ pg_buffercache -
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Real time queries on the shared buffer cache
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by Mark Kirkwood <[email protected]>
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pg_freespacemap -
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Displays the contents of the free space map (FSM)
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by Mark Kirkwood <[email protected]>
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pg_trgm -
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Functions for determining the similarity of text based on trigram
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matching.

‎contrib/pg_freespacemap/Makefile

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# $PostgreSQL: pgsql/contrib/pg_freespacemap/Makefile,v 1.1 2006/02/12 03:55:53 momjian Exp $
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MODULE_big = pg_freespacemap
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OBJS = pg_freespacemap.o
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DATA_built = pg_freespacemap.sql
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DOCS = README.pg_freespacemap
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ifdef USE_PGXS
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PGXS := $(shell pg_config --pgxs)
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include $(PGXS)
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else
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subdir = contrib/pg_freespacemap
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top_builddir = ../..
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include $(top_builddir)/src/Makefile.global
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include $(top_srcdir)/contrib/contrib-global.mk
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endif

‎contrib/pg_freespacemap/README.pg_freespacemap

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Pg_freespacemap - Real time queries on the free space map (FSM).
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---------------
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This module consists of a C function 'pg_freespacemap()' that returns
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a set of records, and a view 'pg_freespacemap' to wrapper the function.
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The module provides the ability to examine the contents of the free space
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map, without having to restart or rebuild the server with additional
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debugging code.
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By default public access is REVOKED from both of these, just in case there
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are security issues lurking.
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Installation
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------------
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Build and install the main Postgresql source, then this contrib module:
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$ cd contrib/pg_freespacemap
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$ gmake
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$ gmake install
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To register the functions:
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$ psql -d <database> -f pg_freespacemap.sql
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Notes
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-----
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The definition of the columns exposed in the view is:
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Column | references | Description
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----------------+----------------------+------------------------------------
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blockid | | Id, 1.. max_fsm_pages
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relfilenode | pg_class.relfilenode | Refilenode of the relation.
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reltablespace | pg_tablespace.oid | Tablespace oid of the relation.
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reldatabase | pg_database.oid | Database for the relation.
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relblocknumber | | Offset of the page in the relation.
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blockfreebytes | | Free bytes in the block/page.
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There is one row for each page in the free space map.
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Because the map is shared by all the databases, there are pages from
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relations not belonging to the current database.
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When the pg_freespacemap view is accessed, internal free space map locks are
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taken, and a copy of the map data is made for the view to display.
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This ensures that the view produces a consistent set of results, while not
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blocking normal activity longer than necessary. Nonetheless there
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could be some impact on database performance if this view is read often.
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Sample output
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-------------
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regression=# \d pg_freespacemap
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View "public.pg_freespacemap"
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Column | Type | Modifiers
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---------------+---------+-----------
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blockid | integer |
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relfilenode | oid |
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reltablespace | oid |
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reldatabase | oid |
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relblocknumber | bigint |
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blockfreebytes | integer |
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View definition:
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SELECT p.blockid, p.relfilenode, p.reltablespace, p.reldatabase, p.relblocknumber, p.blockfreebytes
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FROM pg_freespacemap() p(blockid integer, relfilenode oid, reltablespace oid, reldatabase oid, relblocknumber bigint, blockfreebytes integer);
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regression=# SELECT c.relname, m.relblocknumber, m.blockfreebytes
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FROM pg_freespacemap m INNER JOIN pg_class c
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ON c.relfilenode = m.relfilenode LIMIT 10;
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relname | relblocknumber | blockfreebytes
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------------------------+----------------+----------------
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sql_features | 5 | 2696
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sql_implementation_info | 0 | 7104
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sql_languages | 0 | 8016
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sql_packages | 0 | 7376
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sql_sizing | 0 | 6032
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pg_authid | 0 | 7424
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pg_toast_2618 | 13 | 4588
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pg_toast_2618 | 12 | 1680
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pg_toast_2618 | 10 | 1436
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pg_toast_2618 | 7 | 1136
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(10 rows)
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regression=#
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Author
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------
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* Mark Kirkwood <[email protected]>
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‎contrib/pg_freespacemap/pg_freespacemap.c

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/*-------------------------------------------------------------------------
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*
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* pg_freespacemap.c
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* display some contents of the free space map.
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*
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* $PostgreSQL: pgsql/contrib/pg_freespacemap/pg_freespacemap.c,v 1.1 2006/02/12 03:55:53 momjian Exp $
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "funcapi.h"
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#include "catalog/pg_type.h"
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#include "storage/freespace.h"
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#include "utils/relcache.h"
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#define NUM_FREESPACE_PAGES_ELEM 6
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#if defined(WIN32) || defined(__CYGWIN__)
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extern DLLIMPORT volatile uint32 InterruptHoldoffCount;
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#endif
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Datum pg_freespacemap(PG_FUNCTION_ARGS);
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/*
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* Record structure holding the to be exposed free space data.
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*/
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typedef struct
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{
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uint32 blockid;
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uint32 relfilenode;
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uint32 reltablespace;
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uint32 reldatabase;
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uint32 relblocknumber;
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uint32 blockfreebytes;
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} FreeSpacePagesRec;
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/*
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* Function context for data persisting over repeated calls.
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*/
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typedef struct
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{
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AttInMetadata *attinmeta;
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FreeSpacePagesRec *record;
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char *values[NUM_FREESPACE_PAGES_ELEM];
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} FreeSpacePagesContext;
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/*
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* Function returning data from the Free Space Map (FSM).
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*/
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PG_FUNCTION_INFO_V1(pg_freespacemap);
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Datum
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pg_freespacemap(PG_FUNCTION_ARGS)
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{
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FuncCallContext *funcctx;
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Datum result;
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MemoryContext oldcontext;
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FreeSpacePagesContext *fctx; /* User function context. */
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TupleDesc tupledesc;
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HeapTuple tuple;
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FSMHeader *FreeSpaceMap; /* FSM main structure. */
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FSMRelation *fsmrel; /* Individual relation. */
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if (SRF_IS_FIRSTCALL())
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{
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uint32 i;
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uint32 numPages; /* Max possible no. of pages in map. */
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int nPages; /* Mapped pages for a relation. */
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/*
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* Get the free space map data structure.
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*/
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FreeSpaceMap = GetFreeSpaceMap();
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numPages = MaxFSMPages;
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funcctx = SRF_FIRSTCALL_INIT();
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/* Switch context when allocating stuff to be used in later calls */
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oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
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/* Construct a tuple to return. */
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tupledesc = CreateTemplateTupleDesc(NUM_FREESPACE_PAGES_ELEM, false);
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TupleDescInitEntry(tupledesc, (AttrNumber) 1, "blockid",
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INT4OID, -1, 0);
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TupleDescInitEntry(tupledesc, (AttrNumber) 2, "relfilenode",
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OIDOID, -1, 0);
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TupleDescInitEntry(tupledesc, (AttrNumber) 3, "reltablespace",
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OIDOID, -1, 0);
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TupleDescInitEntry(tupledesc, (AttrNumber) 4, "reldatabase",
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OIDOID, -1, 0);
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TupleDescInitEntry(tupledesc, (AttrNumber) 5, "relblocknumber",
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INT8OID, -1, 0);
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TupleDescInitEntry(tupledesc, (AttrNumber) 6, "blockfreebytes",
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INT4OID, -1, 0);
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/* Generate attribute metadata needed later to produce tuples */
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funcctx->attinmeta = TupleDescGetAttInMetadata(tupledesc);
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/*
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* Create a function context for cross-call persistence and initialize
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* the counters.
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*/
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fctx = (FreeSpacePagesContext *) palloc(sizeof(FreeSpacePagesContext));
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funcctx->user_fctx = fctx;
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/* Set an upper bound on the calls */
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funcctx->max_calls = numPages;
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/* Allocate numPages worth of FreeSpacePagesRec records, this is also
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* an upper bound.
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*/
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fctx->record = (FreeSpacePagesRec *) palloc(sizeof(FreeSpacePagesRec) * numPages);
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/* allocate the strings for tuple formation */
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fctx->values[0] = (char *) palloc(3 * sizeof(uint32) + 1);
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fctx->values[1] = (char *) palloc(3 * sizeof(uint32) + 1);
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fctx->values[2] = (char *) palloc(3 * sizeof(uint32) + 1);
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fctx->values[3] = (char *) palloc(3 * sizeof(uint32) + 1);
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fctx->values[4] = (char *) palloc(3 * sizeof(uint32) + 1);
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fctx->values[5] = (char *) palloc(3 * sizeof(uint32) + 1);
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/* Return to original context when allocating transient memory */
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MemoryContextSwitchTo(oldcontext);
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/*
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* Lock free space map and scan though all the relations,
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* for each relation, gets all its mapped pages.
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*/
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LWLockAcquire(FreeSpaceLock, LW_EXCLUSIVE);
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i = 0;
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for (fsmrel = FreeSpaceMap->usageList; fsmrel; fsmrel = fsmrel->nextUsage)
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{
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if (fsmrel->isIndex)
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{ /* Index relation. */
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IndexFSMPageData *page;
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page = (IndexFSMPageData *)
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(FreeSpaceMap->arena + fsmrel->firstChunk * CHUNKBYTES);
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for (nPages = 0; nPages < fsmrel->storedPages; nPages++)
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{
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fctx->record[i].blockid = i;
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fctx->record[i].relfilenode = fsmrel->key.relNode;
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fctx->record[i].reltablespace = fsmrel->key.spcNode;
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fctx->record[i].reldatabase = fsmrel->key.dbNode;
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fctx->record[i].relblocknumber = IndexFSMPageGetPageNum(page);
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fctx->record[i].blockfreebytes = 0; /* index.*/
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page++;
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i++;
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}
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}
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else
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{ /* Heap relation. */
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FSMPageData *page;
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page = (FSMPageData *)
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(FreeSpaceMap->arena + fsmrel->firstChunk * CHUNKBYTES);
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for (nPages = 0; nPages < fsmrel->storedPages; nPages++)
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{
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fctx->record[i].blockid = i;
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fctx->record[i].relfilenode = fsmrel->key.relNode;
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fctx->record[i].reltablespace = fsmrel->key.spcNode;
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fctx->record[i].reldatabase = fsmrel->key.dbNode;
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fctx->record[i].relblocknumber = FSMPageGetPageNum(page);
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fctx->record[i].blockfreebytes = FSMPageGetSpace(page);
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page++;
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i++;
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}
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}
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}
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/* Set the real no. of calls as we know it now! */
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funcctx->max_calls = i;
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/* Release free space map. */
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LWLockRelease(FreeSpaceLock);
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}
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funcctx = SRF_PERCALL_SETUP();
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/* Get the saved state */
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fctx = funcctx->user_fctx;
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if (funcctx->call_cntr < funcctx->max_calls)
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{
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uint32 i = funcctx->call_cntr;
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sprintf(fctx->values[0], "%u", fctx->record[i].blockid);
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sprintf(fctx->values[1], "%u", fctx->record[i].relfilenode);
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sprintf(fctx->values[2], "%u", fctx->record[i].reltablespace);
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sprintf(fctx->values[3], "%u", fctx->record[i].reldatabase);
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sprintf(fctx->values[4], "%u", fctx->record[i].relblocknumber);
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sprintf(fctx->values[5], "%u", fctx->record[i].blockfreebytes);
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/* Build and return the tuple. */
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tuple = BuildTupleFromCStrings(funcctx->attinmeta, fctx->values);
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result = HeapTupleGetDatum(tuple);
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SRF_RETURN_NEXT(funcctx, result);
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}
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else
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SRF_RETURN_DONE(funcctx);
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}

‎contrib/pg_freespacemap/pg_freespacemap.sql.in

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-- Adjust this setting to control where the objects get created.
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BEGIN;
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SET search_path = public;
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-- Register the function.
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CREATE OR REPLACE FUNCTION pg_freespacemap()
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RETURNS SETOF RECORD
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AS 'MODULE_PATHNAME', 'pg_freespacemap'
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LANGUAGE 'C';
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-- Create a view for convenient access.
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CREATE VIEW pg_freespacemap AS
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SELECT P.* FROM pg_freespacemap() AS P
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(blockid int4, relfilenode oid, reltablespace oid, reldatabase oid, relblocknumber int8, blockfreebytes int4);
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-- Don't want these to be available at public.
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REVOKE ALL ON FUNCTION pg_freespacemap() FROM PUBLIC;
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REVOKE ALL ON pg_freespacemap FROM PUBLIC;
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COMMIT;

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