mirror of https://github.com/postgres/postgres
Bruce Momjian
20 years ago
parent
6c0d4aabe2
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d5dd3d451e
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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 $(top_srcdir)/contrib/contrib-global.mk |
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endif |
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Pg_freespacemap - Real time queries on the free space map (FSM). |
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--------------- |
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This module consists of a C function 'pg_freespacemap()' that returns |
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a set of records, and a view 'pg_freespacemap' to wrapper the function. |
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The module provides the ability to examine the contents of the free space |
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map, without having to restart or rebuild the server with additional |
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debugging code. |
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By default public access is REVOKED from both of these, just in case there |
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are security issues lurking. |
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Installation |
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------------ |
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Build and install the main Postgresql source, then this contrib module: |
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$ 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 <markir@paradise.net.nz> |
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@ -0,0 +1,231 @@ |
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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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} |
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@ -0,0 +1,19 @@ |
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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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