Want to host it on pgfoundry until 8.2 is released?
Mark Kirkwood wrote:
> This patch implements a view to display the free space map contents - e.g :
>
> regression=# SELECT c.relname, m.relblocknumber, m.blockfreebytes
> FROM pg_freespacemap m INNER JOIN pg_class c
> ON c.relfilenode = m.relfilenode LIMIT 10;
> relname | relblocknumber | blockfreebytes
> ------------------------+----------------+----------------
> sql_features | 5 | 2696
> sql_implementation_info | 0 | 7104
> sql_languages | 0 | 8016
> sql_packages | 0 | 7376
> sql_sizing | 0 | 6032
> pg_authid | 0 | 7424
> pg_toast_2618 | 13 | 4588
> pg_toast_2618 | 12 | 1680
> pg_toast_2618 | 10 | 1436
> pg_toast_2618 | 7 | 1136
> (10 rows)
>
> [I found being able to display the FSM pretty cool, even if I say so
> myself....].
>
> It is written as a contrib module (similar to pg_buffercache) so as to
> make any revisions non-initdb requiring.
>
> The code needs to know about several of the (currently) internal data
> structures in freespace.c, so I moved these into freespace.h. Similarly
> for the handy macros to actually compute the free space. Let me know if
> this was the wrong way to proceed!
>
> Additionally access to the FSM pointer itself is required, I added a
> function in freespace.c to return this, rather than making it globally
> visible, again if the latter is a better approach, it is easily changed.
>
> cheers
>
> Mark
>
> P.s : Currently don't have access to a windows box, so had to just 'take
> a stab' at what DLLIMPORTs were required.
>
>
>
> ------------------------------------------------------------------------
>
> diff -Ncar pgsql.orig/contrib/pg_freespacemap/Makefile pgsql/contrib/pg_freespacemap/Makefile
> *** pgsql.orig/contrib/pg_freespacemap/Makefile Thu Jan 1 12:00:00 1970
> --- pgsql/contrib/pg_freespacemap/Makefile Thu Oct 27 17:52:10 2005
> ***************
> *** 0 ****
> --- 1,17 ----
> + # $PostgreSQL$
> +
> + MODULE_big = pg_freespacemap
> + OBJS = pg_freespacemap.o
> +
> + DATA_built = pg_freespacemap.sql
> + DOCS = README.pg_freespacemap
> +
> + ifdef USE_PGXS
> + 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 -Ncar pgsql.orig/contrib/pg_freespacemap/README.pg_freespacemap pgsql/contrib/pg_freespacemap/README.pg_freespacemap
> *** pgsql.orig/contrib/pg_freespacemap/README.pg_freespacemap Thu Jan 1 12:00:00 1970
> --- pgsql/contrib/pg_freespacemap/README.pg_freespacemap Thu Oct 27 18:06:20 2005
> ***************
> *** 0 ****
> --- 1,98 ----
> + Pg_freespacemap - Real time queries on the free space map (FSM).
> + ---------------
> +
> + This module consists of a C function 'pg_freespacemap()' that returns
> + a set of records, and a view 'pg_freespacemap' to wrapper the function.
> +
> + The module provides the ability to examine the contents of the free space
> + map, without having to restart or rebuild the server with additional
> + debugging code.
> +
> + By default public access is REVOKED from both of these, just in case there
> + are security issues lurking.
> +
> +
> + Installation
> + ------------
> +
> + Build and install the main Postgresql source, then this contrib module:
> +
> + $ cd contrib/pg_freespacemap
> + $ gmake
> + $ gmake install
> +
> +
> + To register the functions:
> +
> + $ psql -d <database> -f pg_freespacemap.sql
> +
> +
> + Notes
> + -----
> +
> + The definition of the columns exposed in the view is:
> +
> + Column | references | Description
> + ----------------+----------------------+------------------------------------
> + blockid | | Id, 1.. max_fsm_pages
> + relfilenode | pg_class.relfilenode | Refilenode of the relation.
> + reltablespace | pg_tablespace.oid | Tablespace oid of the relation.
> + reldatabase | pg_database.oid | Database for the relation.
> + relblocknumber | | Offset of the page in the relation.
> + blockfreebytes | | Free bytes in the block/page.
> +
> +
> + There is one row for each page in the free space map.
> +
> + Because the map is shared by all the databases, there are pages from
> + relations not belonging to the current database.
> +
> + When the pg_freespacemap view is accessed, internal free space map locks are
> + taken, and a copy of the map data is made for the view to display.
> + This ensures that the view produces a consistent set of results, while not
> + blocking normal activity longer than necessary. Nonetheless there
> + could be some impact on database performance if this view is read often.
> +
> +
> + Sample output
> + -------------
> +
> + regression=# \d pg_freespacemap
> + View "public.pg_freespacemap"
> + Column | Type | Modifiers
> + ---------------+---------+-----------
> + blockid | integer |
> + relfilenode | oid |
> + reltablespace | oid |
> + reldatabase | oid |
> + relblocknumber | bigint |
> + blockfreebytes | integer |
> + View definition:
> + SELECT p.blockid, p.relfilenode, p.reltablespace, p.reldatabase, p.relblocknumber, p.blockfreebytes
> + FROM pg_freespacemap() p(blockid integer, relfilenode oid, reltablespace oid, reldatabase oid, relblocknumber bigint, blockfreebytes integer);
> +
> + regression=# SELECT c.relname, m.relblocknumber, m.blockfreebytes
> + FROM pg_freespacemap m INNER JOIN pg_class c
> + ON c.relfilenode = m.relfilenode LIMIT 10;
> + relname | relblocknumber | blockfreebytes
> + ------------------------+----------------+----------------
> + sql_features | 5 | 2696
> + sql_implementation_info | 0 | 7104
> + sql_languages | 0 | 8016
> + sql_packages | 0 | 7376
> + sql_sizing | 0 | 6032
> + pg_authid | 0 | 7424
> + pg_toast_2618 | 13 | 4588
> + pg_toast_2618 | 12 | 1680
> + pg_toast_2618 | 10 | 1436
> + pg_toast_2618 | 7 | 1136
> + (10 rows)
> +
> + regression=#
> +
> +
> + Author
> + ------
> +
> + * Mark Kirkwood <markir(at)paradise(dot)net(dot)nz>
> +
> diff -Ncar pgsql.orig/contrib/pg_freespacemap/pg_freespacemap.c pgsql/contrib/pg_freespacemap/pg_freespacemap.c
> *** pgsql.orig/contrib/pg_freespacemap/pg_freespacemap.c Thu Jan 1 12:00:00 1970
> --- pgsql/contrib/pg_freespacemap/pg_freespacemap.c Thu Oct 27 18:07:05 2005
> ***************
> *** 0 ****
> --- 1,231 ----
> + /*-------------------------------------------------------------------------
> + *
> + * pg_freespacemap.c
> + * display some contents of the free space map.
> + *
> + * $PostgreSQL$
> + *-------------------------------------------------------------------------
> + */
> + #include "postgres.h"
> + #include "funcapi.h"
> + #include "catalog/pg_type.h"
> + #include "storage/freespace.h"
> + #include "utils/relcache.h"
> +
> + #define NUM_FREESPACE_PAGES_ELEM 6
> +
> + #if defined(WIN32) || defined(__CYGWIN__)
> + extern DLLIMPORT volatile uint32 InterruptHoldoffCount;
> + #endif
> +
> + Datum pg_freespacemap(PG_FUNCTION_ARGS);
> +
> +
> + /*
> + * Record structure holding the to be exposed free space data.
> + */
> + typedef struct
> + {
> +
> + uint32 blockid;
> + uint32 relfilenode;
> + uint32 reltablespace;
> + uint32 reldatabase;
> + uint32 relblocknumber;
> + uint32 blockfreebytes;
> +
> + } FreeSpacePagesRec;
> +
> +
> + /*
> + * Function context for data persisting over repeated calls.
> + */
> + typedef struct
> + {
> +
> + AttInMetadata *attinmeta;
> + FreeSpacePagesRec *record;
> + char *values[NUM_FREESPACE_PAGES_ELEM];
> +
> + } FreeSpacePagesContext;
> +
> +
> + /*
> + * Function returning data from the Free Space Map (FSM).
> + */
> + PG_FUNCTION_INFO_V1(pg_freespacemap);
> + Datum
> + pg_freespacemap(PG_FUNCTION_ARGS)
> + {
> +
> + FuncCallContext *funcctx;
> + Datum result;
> + MemoryContext oldcontext;
> + FreeSpacePagesContext *fctx; /* User function context. */
> + TupleDesc tupledesc;
> + HeapTuple tuple;
> +
> + FSMHeader *FreeSpaceMap; /* FSM main structure. */
> + FSMRelation *fsmrel; /* Individual relation. */
> +
> +
> + if (SRF_IS_FIRSTCALL())
> + {
> + uint32 i;
> + uint32 numPages; /* Max possible no. of pages in map. */
> + int nPages; /* Mapped pages for a relation. */
> +
> + /*
> + * Get the free space map data structure.
> + */
> + FreeSpaceMap = GetFreeSpaceMap();
> +
> + numPages = MaxFSMPages;
> +
> + funcctx = SRF_FIRSTCALL_INIT();
> +
> + /* Switch context when allocating stuff to be used in later calls */
> + oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
> +
> + /* Construct a tuple to return. */
> + tupledesc = CreateTemplateTupleDesc(NUM_FREESPACE_PAGES_ELEM, false);
> + TupleDescInitEntry(tupledesc, (AttrNumber) 1, "blockid",
> + INT4OID, -1, 0);
> + TupleDescInitEntry(tupledesc, (AttrNumber) 2, "relfilenode",
> + OIDOID, -1, 0);
> + TupleDescInitEntry(tupledesc, (AttrNumber) 3, "reltablespace",
> + OIDOID, -1, 0);
> + TupleDescInitEntry(tupledesc, (AttrNumber) 4, "reldatabase",
> + OIDOID, -1, 0);
> + TupleDescInitEntry(tupledesc, (AttrNumber) 5, "relblocknumber",
> + INT8OID, -1, 0);
> + TupleDescInitEntry(tupledesc, (AttrNumber) 6, "blockfreebytes",
> + INT4OID, -1, 0);
> +
> + /* Generate attribute metadata needed later to produce tuples */
> + funcctx->attinmeta = TupleDescGetAttInMetadata(tupledesc);
> +
> + /*
> + * Create a function context for cross-call persistence and initialize
> + * the counters.
> + */
> + fctx = (FreeSpacePagesContext *) palloc(sizeof(FreeSpacePagesContext));
> + funcctx->user_fctx = fctx;
> +
> + /* Set an upper bound on the calls */
> + funcctx->max_calls = numPages;
> +
> +
> + /* Allocate numPages worth of FreeSpacePagesRec records, this is also
> + * an upper bound.
> + */
> + fctx->record = (FreeSpacePagesRec *) palloc(sizeof(FreeSpacePagesRec) * numPages);
> +
> + /* allocate the strings for tuple formation */
> + fctx->values[0] = (char *) palloc(3 * sizeof(uint32) + 1);
> + fctx->values[1] = (char *) palloc(3 * sizeof(uint32) + 1);
> + fctx->values[2] = (char *) palloc(3 * sizeof(uint32) + 1);
> + fctx->values[3] = (char *) palloc(3 * sizeof(uint32) + 1);
> + fctx->values[4] = (char *) palloc(3 * sizeof(uint32) + 1);
> + fctx->values[5] = (char *) palloc(3 * sizeof(uint32) + 1);
> +
> +
> + /* Return to original context when allocating transient memory */
> + MemoryContextSwitchTo(oldcontext);
> +
> +
> + /*
> + * Lock free space map and scan though all the relations,
> + * for each relation, gets all its mapped pages.
> + */
> + LWLockAcquire(FreeSpaceLock, LW_EXCLUSIVE);
> +
> +
> + i = 0;
> +
> + for (fsmrel = FreeSpaceMap->usageList; fsmrel; fsmrel = fsmrel->nextUsage)
> + {
> +
> + if (fsmrel->isIndex)
> + { /* Index relation. */
> + IndexFSMPageData *page;
> +
> + page = (IndexFSMPageData *)
> + (FreeSpaceMap->arena + fsmrel->firstChunk * CHUNKBYTES);
> +
> + for (nPages = 0; nPages < fsmrel->storedPages; nPages++)
> + {
> +
> + fctx->record[i].blockid = i;
> + fctx->record[i].relfilenode = fsmrel->key.relNode;
> + fctx->record[i].reltablespace = fsmrel->key.spcNode;
> + fctx->record[i].reldatabase = fsmrel->key.dbNode;
> + fctx->record[i].relblocknumber = IndexFSMPageGetPageNum(page);
> + fctx->record[i].blockfreebytes = 0; /* index.*/
> +
> + page++;
> + i++;
> + }
> + }
> + else
> + { /* Heap relation. */
> + FSMPageData *page;
> +
> + page = (FSMPageData *)
> + (FreeSpaceMap->arena + fsmrel->firstChunk * CHUNKBYTES);
> +
> + for (nPages = 0; nPages < fsmrel->storedPages; nPages++)
> + {
> + fctx->record[i].blockid = i;
> + fctx->record[i].relfilenode = fsmrel->key.relNode;
> + fctx->record[i].reltablespace = fsmrel->key.spcNode;
> + fctx->record[i].reldatabase = fsmrel->key.dbNode;
> + fctx->record[i].relblocknumber = FSMPageGetPageNum(page);
> + fctx->record[i].blockfreebytes = FSMPageGetSpace(page);
> +
> + page++;
> + i++;
> + }
> +
> + }
> +
> + }
> +
> + /* Set the real no. of calls as we know it now! */
> + funcctx->max_calls = i;
> +
> + /* Release free space map. */
> + LWLockRelease(FreeSpaceLock);
> + }
> +
> + funcctx = SRF_PERCALL_SETUP();
> +
> + /* Get the saved state */
> + fctx = funcctx->user_fctx;
> +
> +
> + if (funcctx->call_cntr < funcctx->max_calls)
> + {
> + uint32 i = funcctx->call_cntr;
> +
> +
> + sprintf(fctx->values[0], "%u", fctx->record[i].blockid);
> + sprintf(fctx->values[1], "%u", fctx->record[i].relfilenode);
> + sprintf(fctx->values[2], "%u", fctx->record[i].reltablespace);
> + sprintf(fctx->values[3], "%u", fctx->record[i].reldatabase);
> + sprintf(fctx->values[4], "%u", fctx->record[i].relblocknumber);
> + sprintf(fctx->values[5], "%u", fctx->record[i].blockfreebytes);
> +
> +
> +
> + /* Build and return the tuple. */
> + tuple = BuildTupleFromCStrings(funcctx->attinmeta, fctx->values);
> + result = HeapTupleGetDatum(tuple);
> +
> +
> + SRF_RETURN_NEXT(funcctx, result);
> + }
> + else
> + SRF_RETURN_DONE(funcctx);
> +
> + }
> diff -Ncar pgsql.orig/contrib/pg_freespacemap/pg_freespacemap.sql.in pgsql/contrib/pg_freespacemap/pg_freespacemap.sql.in
> *** pgsql.orig/contrib/pg_freespacemap/pg_freespacemap.sql.in Thu Jan 1 12:00:00 1970
> --- pgsql/contrib/pg_freespacemap/pg_freespacemap.sql.in Thu Oct 27 18:07:43 2005
> ***************
> *** 0 ****
> --- 1,17 ----
> + -- Adjust this setting to control where the objects get created.
> + SET search_path = public;
> +
> + -- Register the function.
> + CREATE OR REPLACE FUNCTION pg_freespacemap()
> + RETURNS SETOF RECORD
> + AS 'MODULE_PATHNAME', 'pg_freespacemap'
> + LANGUAGE 'C';
> +
> + -- Create a view for convenient access.
> + CREATE VIEW pg_freespacemap AS
> + SELECT P.* FROM pg_freespacemap() AS P
> + (blockid int4, relfilenode oid, reltablespace oid, reldatabase oid, relblocknumber int8, blockfreebytes int4);
> +
> + -- Don't want these to be available at public.
> + REVOKE ALL ON FUNCTION pg_freespacemap() FROM PUBLIC;
> + REVOKE ALL ON pg_freespacemap FROM PUBLIC;
> diff -Ncar pgsql.orig/src/backend/storage/freespace/freespace.c pgsql/src/backend/storage/freespace/freespace.c
> *** pgsql.orig/src/backend/storage/freespace/freespace.c Thu Oct 20 12:25:06 2005
> --- pgsql/src/backend/storage/freespace/freespace.c Thu Oct 27 17:51:33 2005
> ***************
> *** 71,114 ****
> #include "storage/shmem.h"
>
>
> - /* Initial value for average-request moving average */
> - #define INITIAL_AVERAGE ((Size) (BLCKSZ / 32))
> -
> - /*
> - * Number of pages and bytes per allocation chunk. Indexes can squeeze 50%
> - * more pages into the same space because they don't need to remember how much
> - * free space on each page. The nominal number of pages, CHUNKPAGES, is for
> - * regular rels, and INDEXCHUNKPAGES is for indexes. CHUNKPAGES should be
> - * even so that no space is wasted in the index case.
> - */
> - #define CHUNKPAGES 16
> - #define CHUNKBYTES (CHUNKPAGES * sizeof(FSMPageData))
> - #define INDEXCHUNKPAGES ((int) (CHUNKBYTES / sizeof(IndexFSMPageData)))
> -
> -
> - /*
> - * Typedefs and macros for items in the page-storage arena. We use the
> - * existing ItemPointer and BlockId data structures, which are designed
> - * to pack well (they should be 6 and 4 bytes apiece regardless of machine
> - * alignment issues). Unfortunately we can't use the ItemPointer access
> - * macros, because they include Asserts insisting that ip_posid != 0.
> - */
> - typedef ItemPointerData FSMPageData;
> - typedef BlockIdData IndexFSMPageData;
> -
> - #define FSMPageGetPageNum(ptr) \
> - BlockIdGetBlockNumber(&(ptr)->ip_blkid)
> - #define FSMPageGetSpace(ptr) \
> - ((Size) (ptr)->ip_posid)
> - #define FSMPageSetPageNum(ptr, pg) \
> - BlockIdSet(&(ptr)->ip_blkid, pg)
> - #define FSMPageSetSpace(ptr, sz) \
> - ((ptr)->ip_posid = (OffsetNumber) (sz))
> - #define IndexFSMPageGetPageNum(ptr) \
> - BlockIdGetBlockNumber(ptr)
> - #define IndexFSMPageSetPageNum(ptr, pg) \
> - BlockIdSet(ptr, pg)
> -
> /*----------
> * During database shutdown, we store the contents of FSM into a disk file,
> * which is re-read during startup. This way we don't have a startup
> --- 71,76 ----
> ***************
> *** 156,218 ****
> int32 storedPages; /* # of pages stored in arena */
> } FsmCacheRelHeader;
>
> -
> - /*
> - * Shared free-space-map objects
> - *
> - * The per-relation objects are indexed by a hash table, and are also members
> - * of two linked lists: one ordered by recency of usage (most recent first),
> - * and the other ordered by physical location of the associated storage in
> - * the page-info arena.
> - *
> - * Each relation owns one or more chunks of per-page storage in the "arena".
> - * The chunks for each relation are always consecutive, so that it can treat
> - * its page storage as a simple array. We further insist that its page data
> - * be ordered by block number, so that binary search is possible.
> - *
> - * Note: we handle pointers to these items as pointers, not as SHMEM_OFFSETs.
> - * This assumes that all processes accessing the map will have the shared
> - * memory segment mapped at the same place in their address space.
> - */
> - typedef struct FSMHeader FSMHeader;
> - typedef struct FSMRelation FSMRelation;
> -
> - /* Header for whole map */
> - struct FSMHeader
> - {
> - FSMRelation *usageList; /* FSMRelations in usage-recency order */
> - FSMRelation *usageListTail; /* tail of usage-recency list */
> - FSMRelation *firstRel; /* FSMRelations in arena storage order */
> - FSMRelation *lastRel; /* tail of storage-order list */
> - int numRels; /* number of FSMRelations now in use */
> - double sumRequests; /* sum of requested chunks over all rels */
> - char *arena; /* arena for page-info storage */
> - int totalChunks; /* total size of arena, in chunks */
> - int usedChunks; /* # of chunks assigned */
> - /* NB: there are totalChunks - usedChunks free chunks at end of arena */
> - };
> -
> - /*
> - * Per-relation struct --- this is an entry in the shared hash table.
> - * The hash key is the RelFileNode value (hence, we look at the physical
> - * relation ID, not the logical ID, which is appropriate).
> - */
> - struct FSMRelation
> - {
> - RelFileNode key; /* hash key (must be first) */
> - FSMRelation *nextUsage; /* next rel in usage-recency order */
> - FSMRelation *priorUsage; /* prior rel in usage-recency order */
> - FSMRelation *nextPhysical; /* next rel in arena-storage order */
> - FSMRelation *priorPhysical; /* prior rel in arena-storage order */
> - bool isIndex; /* if true, we store only page numbers */
> - Size avgRequest; /* moving average of space requests */
> - int lastPageCount; /* pages passed to RecordRelationFreeSpace */
> - int firstChunk; /* chunk # of my first chunk in arena */
> - int storedPages; /* # of pages stored in arena */
> - int nextPage; /* index (from 0) to start next search at */
> - };
> -
> -
> int MaxFSMRelations; /* these are set by guc.c */
> int MaxFSMPages;
>
> --- 118,123 ----
> ***************
> *** 1835,1840 ****
> --- 1740,1756 ----
> Assert(fsmrel->firstChunk < 0 && fsmrel->storedPages == 0);
> return 0;
> }
> + }
> +
> +
> + /*
> + * Return the FreeSpaceMap structure for examination.
> + */
> + FSMHeader *
> + GetFreeSpaceMap(void)
> + {
> +
> + return FreeSpaceMap;
> }
>
>
> diff -Ncar pgsql.orig/src/include/storage/freespace.h pgsql/src/include/storage/freespace.h
> *** pgsql.orig/src/include/storage/freespace.h Tue Aug 23 15:56:23 2005
> --- pgsql/src/include/storage/freespace.h Thu Oct 27 17:51:33 2005
> ***************
> *** 16,21 ****
> --- 16,22 ----
>
> #include "storage/block.h"
> #include "storage/relfilenode.h"
> + #include "storage/itemptr.h"
>
>
> /*
> ***************
> *** 28,33 ****
> --- 29,129 ----
> } PageFreeSpaceInfo;
>
>
> + /* Initial value for average-request moving average */
> + #define INITIAL_AVERAGE ((Size) (BLCKSZ / 32))
> +
> + /*
> + * Number of pages and bytes per allocation chunk. Indexes can squeeze 50%
> + * more pages into the same space because they don't need to remember how much
> + * free space on each page. The nominal number of pages, CHUNKPAGES, is for
> + * regular rels, and INDEXCHUNKPAGES is for indexes. CHUNKPAGES should be
> + * even so that no space is wasted in the index case.
> + */
> + #define CHUNKPAGES 16
> + #define CHUNKBYTES (CHUNKPAGES * sizeof(FSMPageData))
> + #define INDEXCHUNKPAGES ((int) (CHUNKBYTES / sizeof(IndexFSMPageData)))
> +
> +
> + /*
> + * Typedefs and macros for items in the page-storage arena. We use the
> + * existing ItemPointer and BlockId data structures, which are designed
> + * to pack well (they should be 6 and 4 bytes apiece regardless of machine
> + * alignment issues). Unfortunately we can't use the ItemPointer access
> + * macros, because they include Asserts insisting that ip_posid != 0.
> + */
> + typedef ItemPointerData FSMPageData;
> + typedef BlockIdData IndexFSMPageData;
> +
> + #define FSMPageGetPageNum(ptr) \
> + BlockIdGetBlockNumber(&(ptr)->ip_blkid)
> + #define FSMPageGetSpace(ptr) \
> + ((Size) (ptr)->ip_posid)
> + #define FSMPageSetPageNum(ptr, pg) \
> + BlockIdSet(&(ptr)->ip_blkid, pg)
> + #define FSMPageSetSpace(ptr, sz) \
> + ((ptr)->ip_posid = (OffsetNumber) (sz))
> + #define IndexFSMPageGetPageNum(ptr) \
> + BlockIdGetBlockNumber(ptr)
> + #define IndexFSMPageSetPageNum(ptr, pg) \
> + BlockIdSet(ptr, pg)
> +
> + /*
> + * Shared free-space-map objects
> + *
> + * The per-relation objects are indexed by a hash table, and are also members
> + * of two linked lists: one ordered by recency of usage (most recent first),
> + * and the other ordered by physical location of the associated storage in
> + * the page-info arena.
> + *
> + * Each relation owns one or more chunks of per-page storage in the "arena".
> + * The chunks for each relation are always consecutive, so that it can treat
> + * its page storage as a simple array. We further insist that its page data
> + * be ordered by block number, so that binary search is possible.
> + *
> + * Note: we handle pointers to these items as pointers, not as SHMEM_OFFSETs.
> + * This assumes that all processes accessing the map will have the shared
> + * memory segment mapped at the same place in their address space.
> + */
> + typedef struct FSMHeader FSMHeader;
> + typedef struct FSMRelation FSMRelation;
> +
> + /* Header for whole map */
> + struct FSMHeader
> + {
> + FSMRelation *usageList; /* FSMRelations in usage-recency order */
> + FSMRelation *usageListTail; /* tail of usage-recency list */
> + FSMRelation *firstRel; /* FSMRelations in arena storage order */
> + FSMRelation *lastRel; /* tail of storage-order list */
> + int numRels; /* number of FSMRelations now in use */
> + double sumRequests; /* sum of requested chunks over all rels */
> + char *arena; /* arena for page-info storage */
> + int totalChunks; /* total size of arena, in chunks */
> + int usedChunks; /* # of chunks assigned */
> + /* NB: there are totalChunks - usedChunks free chunks at end of arena */
> + };
> +
> + /*
> + * Per-relation struct --- this is an entry in the shared hash table.
> + * The hash key is the RelFileNode value (hence, we look at the physical
> + * relation ID, not the logical ID, which is appropriate).
> + */
> + struct FSMRelation
> + {
> + RelFileNode key; /* hash key (must be first) */
> + FSMRelation *nextUsage; /* next rel in usage-recency order */
> + FSMRelation *priorUsage; /* prior rel in usage-recency order */
> + FSMRelation *nextPhysical; /* next rel in arena-storage order */
> + FSMRelation *priorPhysical; /* prior rel in arena-storage order */
> + bool isIndex; /* if true, we store only page numbers */
> + Size avgRequest; /* moving average of space requests */
> + int lastPageCount; /* pages passed to RecordRelationFreeSpace */
> + int firstChunk; /* chunk # of my first chunk in arena */
> + int storedPages; /* # of pages stored in arena */
> + int nextPage; /* index (from 0) to start next search at */
> + };
> +
> +
> +
> /* GUC variables */
> extern int MaxFSMRelations;
> extern int MaxFSMPages;
> ***************
> *** 62,67 ****
> --- 158,164 ----
>
> extern void DumpFreeSpaceMap(int code, Datum arg);
> extern void LoadFreeSpaceMap(void);
> + extern FSMHeader *GetFreeSpaceMap(void);
>
> #ifdef FREESPACE_DEBUG
> extern void DumpFreeSpace(void);
>
>
>
> ------------------------------------------------------------------------
>
>
> ---------------------------(end of broadcast)---------------------------
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