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d70610c4ee
layout; therefore, this change forces REINDEX of hash indexes (though not a full initdb). Widen hashm_ntuples to double so that hash space management doesn't get confused by more than 4G entries; enlarge the allowed number of free-space-bitmap pages; replace the useless bshift field with a useful bmshift field; eliminate 4 bytes of wasted space in the per-page special area.
292 lines
10 KiB
C
292 lines
10 KiB
C
/*-------------------------------------------------------------------------
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*
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* hash.h
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* header file for postgres hash access method implementation
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*
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*
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* Portions Copyright (c) 1996-2003, 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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* $Id: hash.h,v 1.52 2003/09/02 18:13:32 tgl Exp $
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*
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* NOTES
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* modeled after Margo Seltzer's hash implementation for unix.
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef HASH_H
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#define HASH_H
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#include "access/itup.h"
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#include "access/relscan.h"
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#include "access/sdir.h"
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#include "access/xlog.h"
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#include "fmgr.h"
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/*
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* Mapping from hash bucket number to physical block number of bucket's
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* starting page. Beware of multiple evaluations of argument!
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*/
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typedef uint32 Bucket;
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#define BUCKET_TO_BLKNO(metap,B) \
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((BlockNumber) ((B) + ((B) ? (metap)->hashm_spares[_hash_log2((B)+1)-1] : 0)) + 1)
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/*
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* Special space for hash index pages.
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*
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* hasho_flag tells us which type of page we're looking at. For
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* example, knowing overflow pages from bucket pages is necessary
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* information when you're deleting tuples from a page. If all the
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* tuples are deleted from an overflow page, the overflow is made
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* available to other buckets by calling _hash_freeovflpage(). If all
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* the tuples are deleted from a bucket page, no additional action is
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* necessary.
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*/
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#define LH_UNUSED_PAGE (0)
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#define LH_OVERFLOW_PAGE (1 << 0)
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#define LH_BUCKET_PAGE (1 << 1)
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#define LH_BITMAP_PAGE (1 << 2)
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#define LH_META_PAGE (1 << 3)
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typedef struct HashPageOpaqueData
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{
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BlockNumber hasho_prevblkno; /* previous ovfl (or bucket) blkno */
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BlockNumber hasho_nextblkno; /* next ovfl blkno */
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Bucket hasho_bucket; /* bucket number this pg belongs to */
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uint16 hasho_flag; /* page type code, see above */
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uint16 hasho_filler; /* available for future use */
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/*
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* We presently set hasho_filler to HASHO_FILL (0x1234); this is for
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* the convenience of pg_filedump, which otherwise would have a hard
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* time telling HashPageOpaqueData from BTPageOpaqueData. If we ever
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* need that space for some other purpose, pg_filedump will have to
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* find another way.
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*/
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} HashPageOpaqueData;
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typedef HashPageOpaqueData *HashPageOpaque;
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#define HASHO_FILL 0x1234
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/*
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* ScanOpaqueData is used to remember which buffers we're currently
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* examining in the scan. We keep these buffers locked and pinned and
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* recorded in the opaque entry of the scan in order to avoid doing a
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* ReadBuffer() for every tuple in the index.
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*/
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typedef struct HashScanOpaqueData
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{
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Buffer hashso_curbuf;
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Buffer hashso_mrkbuf;
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} HashScanOpaqueData;
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typedef HashScanOpaqueData *HashScanOpaque;
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/*
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* Definitions for metapage.
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*/
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#define HASH_METAPAGE 0 /* metapage is always block 0 */
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#define HASH_MAGIC 0x6440640
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#define HASH_VERSION 1 /* new for Pg 7.4 */
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/*
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* Spares[] holds the number of overflow pages currently allocated at or
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* before a certain splitpoint. For example, if spares[3] = 7 then there are
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* 7 ovflpages before splitpoint 3 (compare BUCKET_TO_BLKNO macro). The
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* value in spares[ovflpoint] increases as overflow pages are added at the
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* end of the index. Once ovflpoint increases (ie, we have actually allocated
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* the bucket pages belonging to that splitpoint) the number of spares at the
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* prior splitpoint cannot change anymore.
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*
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* ovflpages that have been recycled for reuse can be found by looking at
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* bitmaps that are stored within ovflpages dedicated for the purpose.
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* The blknos of these bitmap pages are kept in bitmaps[]; nmaps is the
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* number of currently existing bitmaps.
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*
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* The limitation on the size of spares[] comes from the fact that there's
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* no point in having more than 2^32 buckets with only uint32 hashcodes.
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* There is no particular upper limit on the size of mapp[], other than
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* needing to fit into the metapage. (With 8K block size, 128 bitmaps
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* limit us to 64 Gb of overflow space...)
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*/
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#define HASH_MAX_SPLITPOINTS 32
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#define HASH_MAX_BITMAPS 128
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typedef struct HashMetaPageData
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{
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PageHeaderData hashm_phdr; /* pad for page header (do not use) */
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uint32 hashm_magic; /* magic no. for hash tables */
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uint32 hashm_version; /* version ID */
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double hashm_ntuples; /* number of tuples stored in the table */
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uint16 hashm_ffactor; /* target fill factor (tuples/bucket) */
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uint16 hashm_bsize; /* index page size (bytes) */
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uint16 hashm_bmsize; /* bitmap array size (bytes) - must be a
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* power of 2 */
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uint16 hashm_bmshift; /* log2(bitmap array size in BITS) */
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uint32 hashm_maxbucket; /* ID of maximum bucket in use */
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uint32 hashm_highmask; /* mask to modulo into entire table */
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uint32 hashm_lowmask; /* mask to modulo into lower half of table */
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uint32 hashm_ovflpoint;/* splitpoint from which ovflpgs being
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* allocated */
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uint32 hashm_firstfree; /* lowest-number free ovflpage (bit#) */
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uint32 hashm_nmaps; /* number of bitmap pages */
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RegProcedure hashm_procid; /* hash procedure id from pg_proc */
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uint32 hashm_spares[HASH_MAX_SPLITPOINTS]; /* spare pages before
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* each splitpoint */
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BlockNumber hashm_mapp[HASH_MAX_BITMAPS]; /* blknos of ovfl bitmaps */
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} HashMetaPageData;
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typedef HashMetaPageData *HashMetaPage;
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typedef struct HashItemData
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{
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IndexTupleData hash_itup;
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} HashItemData;
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typedef HashItemData *HashItem;
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/*
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* Constants
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*/
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#define DEFAULT_FFACTOR 300
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#define BYTE_TO_BIT 3 /* 2^3 bits/byte */
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#define ALL_SET ((uint32) ~0)
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/*
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* Bitmap pages do not contain tuples. They do contain the standard
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* page headers and trailers; however, everything in between is a
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* giant bit array. The number of bits that fit on a page obviously
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* depends on the page size and the header/trailer overhead. We require
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* the number of bits per page to be a power of 2.
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*/
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#define BMPGSZ_BYTE(metap) ((metap)->hashm_bmsize)
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#define BMPGSZ_BIT(metap) ((metap)->hashm_bmsize << BYTE_TO_BIT)
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#define BMPG_SHIFT(metap) ((metap)->hashm_bmshift)
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#define BMPG_MASK(metap) (BMPGSZ_BIT(metap) - 1)
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#define HashPageGetBitmap(pg) \
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((uint32 *) (((char *) (pg)) + MAXALIGN(sizeof(PageHeaderData))))
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/*
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* The number of bits in an ovflpage bitmap word.
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*/
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#define BITS_PER_MAP 32 /* Number of bits in uint32 */
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/* Given the address of the beginning of a bit map, clear/set the nth bit */
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#define CLRBIT(A, N) ((A)[(N)/BITS_PER_MAP] &= ~(1<<((N)%BITS_PER_MAP)))
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#define SETBIT(A, N) ((A)[(N)/BITS_PER_MAP] |= (1<<((N)%BITS_PER_MAP)))
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#define ISSET(A, N) ((A)[(N)/BITS_PER_MAP] & (1<<((N)%BITS_PER_MAP)))
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/*
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* page locking modes
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*/
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#define HASH_READ 0
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#define HASH_WRITE 1
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/*
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* Strategy number. There's only one valid strategy for hashing: equality.
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*/
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#define HTEqualStrategyNumber 1
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#define HTMaxStrategyNumber 1
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/*
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* When a new operator class is declared, we require that the user supply
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* us with an amproc procudure for hashing a key of the new type.
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* Since we only have one such proc in amproc, it's number 1.
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*/
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#define HASHPROC 1
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extern bool BuildingHash;
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/* public routines */
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extern Datum hashbuild(PG_FUNCTION_ARGS);
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extern Datum hashinsert(PG_FUNCTION_ARGS);
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extern Datum hashgettuple(PG_FUNCTION_ARGS);
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extern Datum hashbeginscan(PG_FUNCTION_ARGS);
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extern Datum hashrescan(PG_FUNCTION_ARGS);
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extern Datum hashendscan(PG_FUNCTION_ARGS);
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extern Datum hashmarkpos(PG_FUNCTION_ARGS);
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extern Datum hashrestrpos(PG_FUNCTION_ARGS);
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extern Datum hashbulkdelete(PG_FUNCTION_ARGS);
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/*
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* Datatype-specific hash functions in hashfunc.c.
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*
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* These support both hash indexes and hash joins.
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*
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* NOTE: some of these are also used by catcache operations, without
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* any direct connection to hash indexes. Also, the common hash_any
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* routine is also used by dynahash tables.
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*/
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extern Datum hashchar(PG_FUNCTION_ARGS);
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extern Datum hashint2(PG_FUNCTION_ARGS);
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extern Datum hashint4(PG_FUNCTION_ARGS);
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extern Datum hashint8(PG_FUNCTION_ARGS);
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extern Datum hashoid(PG_FUNCTION_ARGS);
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extern Datum hashfloat4(PG_FUNCTION_ARGS);
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extern Datum hashfloat8(PG_FUNCTION_ARGS);
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extern Datum hashoidvector(PG_FUNCTION_ARGS);
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extern Datum hashint2vector(PG_FUNCTION_ARGS);
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extern Datum hashname(PG_FUNCTION_ARGS);
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extern Datum hashtext(PG_FUNCTION_ARGS);
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extern Datum hashvarlena(PG_FUNCTION_ARGS);
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extern Datum hash_any(register const unsigned char *k, register int keylen);
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/* private routines */
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/* hashinsert.c */
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extern InsertIndexResult _hash_doinsert(Relation rel, HashItem hitem);
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/* hashovfl.c */
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extern Buffer _hash_addovflpage(Relation rel, Buffer metabuf, Buffer buf);
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extern BlockNumber _hash_freeovflpage(Relation rel, Buffer ovflbuf);
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extern void _hash_initbitmap(Relation rel, HashMetaPage metap,
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BlockNumber blkno);
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extern void _hash_squeezebucket(Relation rel,
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Bucket bucket, BlockNumber bucket_blkno);
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/* hashpage.c */
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extern void _hash_metapinit(Relation rel);
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extern Buffer _hash_getbuf(Relation rel, BlockNumber blkno, int access);
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extern void _hash_relbuf(Relation rel, Buffer buf, int access);
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extern void _hash_wrtbuf(Relation rel, Buffer buf);
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extern void _hash_wrtnorelbuf(Buffer buf);
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extern void _hash_chgbufaccess(Relation rel, Buffer buf, int from_access,
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int to_access);
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extern void _hash_pageinit(Page page, Size size);
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extern void _hash_expandtable(Relation rel, Buffer metabuf);
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/* hashscan.c */
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extern void _hash_regscan(IndexScanDesc scan);
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extern void _hash_dropscan(IndexScanDesc scan);
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extern void _hash_adjscans(Relation rel, ItemPointer tid);
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extern void AtEOXact_hash(void);
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/* hashsearch.c */
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extern void _hash_search(Relation rel, int keysz, ScanKey scankey,
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Buffer *bufP, HashMetaPage metap);
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extern bool _hash_next(IndexScanDesc scan, ScanDirection dir);
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extern bool _hash_first(IndexScanDesc scan, ScanDirection dir);
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extern bool _hash_step(IndexScanDesc scan, Buffer *bufP, ScanDirection dir,
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Buffer metabuf);
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/* hashutil.c */
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extern ScanKey _hash_mkscankey(Relation rel, IndexTuple itup);
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extern void _hash_freeskey(ScanKey skey);
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extern bool _hash_checkqual(IndexScanDesc scan, IndexTuple itup);
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extern HashItem _hash_formitem(IndexTuple itup);
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extern Bucket _hash_call(Relation rel, HashMetaPage metap, Datum key);
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extern uint32 _hash_log2(uint32 num);
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extern void _hash_checkpage(Relation rel, Page page, int flags);
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/* hash.c */
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extern void hash_redo(XLogRecPtr lsn, XLogRecord *record);
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extern void hash_undo(XLogRecPtr lsn, XLogRecord *record);
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extern void hash_desc(char *buf, uint8 xl_info, char *rec);
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#endif /* HASH_H */
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