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Rewrite the FSM. Instead of relying on a fixed-size shared memory segment, the
free space information is stored in a dedicated FSM relation fork, with each relation (except for hash indexes; they don't use FSM). This eliminates the max_fsm_relations and max_fsm_pages GUC options; remove any trace of them from the backend, initdb, and documentation. Rewrite contrib/pg_freespacemap to match the new FSM implementation. Also introduce a new variant of the get_raw_page(regclass, int4, int4) function in contrib/pageinspect that let's you to return pages from any relation fork, and a new fsm_page_contents() function to inspect the new FSM pages.
This commit is contained in:
Heikki Linnakangas
@@ -7,152 +7,32 @@
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* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/storage/freespace.h,v 1.28 2008/03/10 02:04:10 tgl Exp $
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* $PostgreSQL: pgsql/src/include/storage/freespace.h,v 1.29 2008/09/30 10:52:13 heikki Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef FREESPACE_H_
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#define FREESPACE_H_
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#include "storage/relfilenode.h"
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#include "storage/itemptr.h"
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#include "utils/rel.h"
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#include "storage/bufpage.h"
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#include "access/xlog.h"
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/* Initial value for average-request moving average */
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#define INITIAL_AVERAGE ((Size) (BLCKSZ / 32))
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/*
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* Number of pages and bytes per allocation chunk. Indexes can squeeze 50%
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* more pages into the same space because they don't need to remember how much
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* free space on each page. The nominal number of pages, CHUNKPAGES, is for
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* regular rels, and INDEXCHUNKPAGES is for indexes. CHUNKPAGES should be
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* even so that no space is wasted in the index case.
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*/
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#define CHUNKPAGES 16
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#define CHUNKBYTES (CHUNKPAGES * sizeof(FSMPageData))
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#define INDEXCHUNKPAGES ((int) (CHUNKBYTES / sizeof(IndexFSMPageData)))
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/*
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* Typedefs and macros for items in the page-storage arena. We use the
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* existing ItemPointer and BlockId data structures, which are designed
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* to pack well (they should be 6 and 4 bytes apiece regardless of machine
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* alignment issues). Unfortunately we can't use the ItemPointer access
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* macros, because they include Asserts insisting that ip_posid != 0.
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*/
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typedef ItemPointerData FSMPageData;
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typedef BlockIdData IndexFSMPageData;
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#define FSMPageGetPageNum(ptr) \
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BlockIdGetBlockNumber(&(ptr)->ip_blkid)
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#define FSMPageGetSpace(ptr) \
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((Size) (ptr)->ip_posid)
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#define FSMPageSetPageNum(ptr, pg) \
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BlockIdSet(&(ptr)->ip_blkid, pg)
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#define FSMPageSetSpace(ptr, sz) \
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((ptr)->ip_posid = (OffsetNumber) (sz))
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#define IndexFSMPageGetPageNum(ptr) \
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BlockIdGetBlockNumber(ptr)
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#define IndexFSMPageSetPageNum(ptr, pg) \
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BlockIdSet(ptr, pg)
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/*
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* Shared free-space-map objects
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*
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* The per-relation objects are indexed by a hash table, and are also members
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* of two linked lists: one ordered by recency of usage (most recent first),
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* and the other ordered by physical location of the associated storage in
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* the page-info arena.
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*
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* Each relation owns one or more chunks of per-page storage in the "arena".
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* The chunks for each relation are always consecutive, so that it can treat
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* its page storage as a simple array. We further insist that its page data
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* be ordered by block number, so that binary search is possible.
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*
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* Note: we handle pointers to these items as pointers, not as SHMEM_OFFSETs.
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* This assumes that all processes accessing the map will have the shared
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* memory segment mapped at the same place in their address space.
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*/
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typedef struct FSMHeader FSMHeader;
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typedef struct FSMRelation FSMRelation;
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/* Header for whole map */
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struct FSMHeader
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{
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FSMRelation *usageList; /* FSMRelations in usage-recency order */
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FSMRelation *usageListTail; /* tail of usage-recency list */
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FSMRelation *firstRel; /* FSMRelations in arena storage order */
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FSMRelation *lastRel; /* tail of storage-order list */
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int numRels; /* number of FSMRelations now in use */
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double sumRequests; /* sum of requested chunks over all rels */
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char *arena; /* arena for page-info storage */
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int totalChunks; /* total size of arena, in chunks */
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int usedChunks; /* # of chunks assigned */
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/* NB: there are totalChunks - usedChunks free chunks at end of arena */
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};
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/*
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* Per-relation struct --- this is an entry in the shared hash table.
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* The hash key is the RelFileNode value (hence, we look at the physical
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* relation ID, not the logical ID, which is appropriate).
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*/
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struct FSMRelation
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{
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RelFileNode key; /* hash key (must be first) */
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FSMRelation *nextUsage; /* next rel in usage-recency order */
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FSMRelation *priorUsage; /* prior rel in usage-recency order */
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FSMRelation *nextPhysical; /* next rel in arena-storage order */
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FSMRelation *priorPhysical; /* prior rel in arena-storage order */
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bool isIndex; /* if true, we store only page numbers */
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Size avgRequest; /* moving average of space requests */
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BlockNumber interestingPages; /* # of pages with useful free space */
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int firstChunk; /* chunk # of my first chunk in arena */
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int storedPages; /* # of pages stored in arena */
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int nextPage; /* index (from 0) to start next search at */
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};
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/* GUC variables */
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extern PGDLLIMPORT int MaxFSMRelations;
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extern PGDLLIMPORT int MaxFSMPages;
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/*
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* function prototypes
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*/
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extern void InitFreeSpaceMap(void);
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extern Size FreeSpaceShmemSize(void);
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extern FSMHeader *GetFreeSpaceMap(void);
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extern BlockNumber GetPageWithFreeSpace(RelFileNode *rel, Size spaceNeeded);
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extern BlockNumber RecordAndGetPageWithFreeSpace(RelFileNode *rel,
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/* prototypes for public functions in freespace.c */
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extern Size GetRecordedFreeSpace(Relation rel, BlockNumber heapBlk);
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extern BlockNumber GetPageWithFreeSpace(Relation rel, Size spaceNeeded);
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extern BlockNumber RecordAndGetPageWithFreeSpace(Relation rel,
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BlockNumber oldPage,
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Size oldSpaceAvail,
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Size spaceNeeded);
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extern Size GetAvgFSMRequestSize(RelFileNode *rel);
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extern void RecordRelationFreeSpace(RelFileNode *rel,
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BlockNumber interestingPages,
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int nPages,
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FSMPageData *pageSpaces);
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extern void RecordPageWithFreeSpace(Relation rel, BlockNumber heapBlk,
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Size spaceAvail);
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extern BlockNumber GetFreeIndexPage(RelFileNode *rel);
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extern void RecordIndexFreeSpace(RelFileNode *rel,
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BlockNumber interestingPages,
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int nPages,
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BlockNumber *pages);
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extern void FreeSpaceMapTruncateRel(Relation rel, BlockNumber nblocks);
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extern void FreeSpaceMapVacuum(Relation rel);
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extern void FreeSpaceMapTruncateRel(RelFileNode *rel, BlockNumber nblocks);
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extern void FreeSpaceMapForgetRel(RelFileNode *rel);
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extern void FreeSpaceMapForgetDatabase(Oid dbid);
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extern void PrintFreeSpaceMapStatistics(int elevel);
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extern void DumpFreeSpaceMap(int code, Datum arg);
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extern void LoadFreeSpaceMap(void);
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#ifdef FREESPACE_DEBUG
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extern void DumpFreeSpace(void);
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#endif
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/* WAL prototypes */
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extern void fsm_desc(StringInfo buf, uint8 xl_info, char *rec);
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extern void fsm_redo(XLogRecPtr lsn, XLogRecord *record);
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#endif /* FREESPACE_H */
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