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/*-------------------------------------------------------------------------
*
* hash.h
* header file for postgres hash access method implementation
*
*
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/hash.h,v 1.84 2008/01/01 19:45:56 momjian Exp $
*
* NOTES
* modeled after Margo Seltzer's hash implementation for unix.
*
*-------------------------------------------------------------------------
*/
#ifndef HASH_H
#define HASH_H
#include "access/itup.h"
#include "access/relscan.h"
#include "access/sdir.h"
#include "access/xlog.h"
#include "fmgr.h"
#include "storage/lock.h"
/*
* Mapping from hash bucket number to physical block number of bucket's
* starting page. Beware of multiple evaluations of argument!
*/
typedef uint32 Bucket;
#define BUCKET_TO_BLKNO(metap,B) \
((BlockNumber) ((B) + ((B) ? (metap)->hashm_spares[_hash_log2((B)+1)-1] : 0)) + 1)
/*
* Special space for hash index pages.
*
* hasho_flag tells us which type of page we're looking at. For
* example, knowing overflow pages from bucket pages is necessary
* information when you're deleting tuples from a page. If all the
* tuples are deleted from an overflow page, the overflow is made
* available to other buckets by calling _hash_freeovflpage(). If all
* the tuples are deleted from a bucket page, no additional action is
* necessary.
*/
#define LH_UNUSED_PAGE (0)
#define LH_OVERFLOW_PAGE (1 << 0)
#define LH_BUCKET_PAGE (1 << 1)
#define LH_BITMAP_PAGE (1 << 2)
#define LH_META_PAGE (1 << 3)
typedef struct HashPageOpaqueData
{
BlockNumber hasho_prevblkno; /* previous ovfl (or bucket) blkno */
BlockNumber hasho_nextblkno; /* next ovfl blkno */
Bucket hasho_bucket; /* bucket number this pg belongs to */
uint16 hasho_flag; /* page type code, see above */
uint16 hasho_page_id; /* for identification of hash indexes */
} HashPageOpaqueData;
typedef HashPageOpaqueData *HashPageOpaque;
/*
* The page ID is for the convenience of pg_filedump and similar utilities,
* which otherwise would have a hard time telling pages of different index
* types apart. It should be the last 2 bytes on the page. This is more or
* less "free" due to alignment considerations.
*/
#define HASHO_PAGE_ID 0xFF80
/*
* HashScanOpaqueData is private state for a hash index scan.
*/
typedef struct HashScanOpaqueData
{
/*
* By definition, a hash scan should be examining only one bucket. We
* record the bucket number here as soon as it is known.
*/
Bucket hashso_bucket;
bool hashso_bucket_valid;
/*
* If we have a share lock on the bucket, we record it here. When
* hashso_bucket_blkno is zero, we have no such lock.
*/
BlockNumber hashso_bucket_blkno;
/*
* We also want to remember which buffers we're currently examining in the
* scan. We keep these buffers pinned (but not locked) across hashgettuple
* calls, in order to avoid doing a ReadBuffer() for every tuple in the
* index.
*/
Buffer hashso_curbuf;
Buffer hashso_mrkbuf;
/* Current and marked position of the scan */
ItemPointerData hashso_curpos;
ItemPointerData hashso_mrkpos;
} HashScanOpaqueData;
typedef HashScanOpaqueData *HashScanOpaque;
/*
* Definitions for metapage.
*/
#define HASH_METAPAGE 0 /* metapage is always block 0 */
#define HASH_MAGIC 0x6440640
#define HASH_VERSION 1 /* new for Pg 7.4 */
/*
* Spares[] holds the number of overflow pages currently allocated at or
* before a certain splitpoint. For example, if spares[3] = 7 then there are
* 7 ovflpages before splitpoint 3 (compare BUCKET_TO_BLKNO macro). The
* value in spares[ovflpoint] increases as overflow pages are added at the
* end of the index. Once ovflpoint increases (ie, we have actually allocated
* the bucket pages belonging to that splitpoint) the number of spares at the
* prior splitpoint cannot change anymore.
*
* ovflpages that have been recycled for reuse can be found by looking at
* bitmaps that are stored within ovflpages dedicated for the purpose.
* The blknos of these bitmap pages are kept in bitmaps[]; nmaps is the
* number of currently existing bitmaps.
*
* The limitation on the size of spares[] comes from the fact that there's
* no point in having more than 2^32 buckets with only uint32 hashcodes.
* There is no particular upper limit on the size of mapp[], other than
* needing to fit into the metapage. (With 8K block size, 128 bitmaps
* limit us to 64 Gb of overflow space...)
*/
#define HASH_MAX_SPLITPOINTS 32
#define HASH_MAX_BITMAPS 128
typedef struct HashMetaPageData
{
PageHeaderData hashm_phdr; /* pad for page header (do not use) */
uint32 hashm_magic; /* magic no. for hash tables */
uint32 hashm_version; /* version ID */
double hashm_ntuples; /* number of tuples stored in the table */
uint16 hashm_ffactor; /* target fill factor (tuples/bucket) */
uint16 hashm_bsize; /* index page size (bytes) */
uint16 hashm_bmsize; /* bitmap array size (bytes) - must be a power
* of 2 */
uint16 hashm_bmshift; /* log2(bitmap array size in BITS) */
uint32 hashm_maxbucket; /* ID of maximum bucket in use */
uint32 hashm_highmask; /* mask to modulo into entire table */
uint32 hashm_lowmask; /* mask to modulo into lower half of table */
uint32 hashm_ovflpoint;/* splitpoint from which ovflpgs being
* allocated */
uint32 hashm_firstfree; /* lowest-number free ovflpage (bit#) */
uint32 hashm_nmaps; /* number of bitmap pages */
RegProcedure hashm_procid; /* hash procedure id from pg_proc */
uint32 hashm_spares[HASH_MAX_SPLITPOINTS]; /* spare pages before
* each splitpoint */
BlockNumber hashm_mapp[HASH_MAX_BITMAPS]; /* blknos of ovfl bitmaps */
} HashMetaPageData;
typedef HashMetaPageData *HashMetaPage;
/*
* Maximum size of a hash index item (it's okay to have only one per page)
*/
#define HashMaxItemSize(page) \
(PageGetPageSize(page) - \
sizeof(PageHeaderData) - \
MAXALIGN(sizeof(HashPageOpaqueData)) - \
sizeof(ItemIdData))
#define HASH_MIN_FILLFACTOR 10
#define HASH_DEFAULT_FILLFACTOR 75
/*
* Constants
*/
#define BYTE_TO_BIT 3 /* 2^3 bits/byte */
#define ALL_SET ((uint32) ~0)
/*
* Bitmap pages do not contain tuples. They do contain the standard
* page headers and trailers; however, everything in between is a
* giant bit array. The number of bits that fit on a page obviously
* depends on the page size and the header/trailer overhead. We require
* the number of bits per page to be a power of 2.
*/
#define BMPGSZ_BYTE(metap) ((metap)->hashm_bmsize)
#define BMPGSZ_BIT(metap) ((metap)->hashm_bmsize << BYTE_TO_BIT)
#define BMPG_SHIFT(metap) ((metap)->hashm_bmshift)
#define BMPG_MASK(metap) (BMPGSZ_BIT(metap) - 1)
#define HashPageGetBitmap(pg) \
((uint32 *) (((char *) (pg)) + MAXALIGN(sizeof(PageHeaderData))))
/*
* The number of bits in an ovflpage bitmap word.
*/
#define BITS_PER_MAP 32 /* Number of bits in uint32 */
/* Given the address of the beginning of a bit map, clear/set the nth bit */
#define CLRBIT(A, N) ((A)[(N)/BITS_PER_MAP] &= ~(1<<((N)%BITS_PER_MAP)))
#define SETBIT(A, N) ((A)[(N)/BITS_PER_MAP] |= (1<<((N)%BITS_PER_MAP)))
#define ISSET(A, N) ((A)[(N)/BITS_PER_MAP] & (1<<((N)%BITS_PER_MAP)))
/*
* page-level and high-level locking modes (see README)
*/
#define HASH_READ BUFFER_LOCK_SHARE
#define HASH_WRITE BUFFER_LOCK_EXCLUSIVE
#define HASH_NOLOCK (-1)
#define HASH_SHARE ShareLock
#define HASH_EXCLUSIVE ExclusiveLock
/*
* Strategy number. There's only one valid strategy for hashing: equality.
*/
#define HTEqualStrategyNumber 1
#define HTMaxStrategyNumber 1
/*
* When a new operator class is declared, we require that the user supply
* us with an amproc procudure for hashing a key of the new type.
* Since we only have one such proc in amproc, it's number 1.
*/
#define HASHPROC 1
/* public routines */
extern Datum hashbuild(PG_FUNCTION_ARGS);
extern Datum hashinsert(PG_FUNCTION_ARGS);
extern Datum hashbeginscan(PG_FUNCTION_ARGS);
extern Datum hashgettuple(PG_FUNCTION_ARGS);
extern Datum hashgetmulti(PG_FUNCTION_ARGS);
extern Datum hashrescan(PG_FUNCTION_ARGS);
extern Datum hashendscan(PG_FUNCTION_ARGS);
extern Datum hashmarkpos(PG_FUNCTION_ARGS);
extern Datum hashrestrpos(PG_FUNCTION_ARGS);
extern Datum hashbulkdelete(PG_FUNCTION_ARGS);
extern Datum hashvacuumcleanup(PG_FUNCTION_ARGS);
extern Datum hashoptions(PG_FUNCTION_ARGS);
/*
* Datatype-specific hash functions in hashfunc.c.
*
* These support both hash indexes and hash joins.
*
* NOTE: some of these are also used by catcache operations, without
* any direct connection to hash indexes. Also, the common hash_any
* routine is also used by dynahash tables.
*/
extern Datum hashchar(PG_FUNCTION_ARGS);
extern Datum hashint2(PG_FUNCTION_ARGS);
extern Datum hashint4(PG_FUNCTION_ARGS);
extern Datum hashint8(PG_FUNCTION_ARGS);
extern Datum hashoid(PG_FUNCTION_ARGS);
extern Datum hashenum(PG_FUNCTION_ARGS);
extern Datum hashfloat4(PG_FUNCTION_ARGS);
extern Datum hashfloat8(PG_FUNCTION_ARGS);
extern Datum hashoidvector(PG_FUNCTION_ARGS);
extern Datum hashint2vector(PG_FUNCTION_ARGS);
extern Datum hashname(PG_FUNCTION_ARGS);
extern Datum hashtext(PG_FUNCTION_ARGS);
extern Datum hashvarlena(PG_FUNCTION_ARGS);
extern Datum hash_any(register const unsigned char *k, register int keylen);
extern Datum hash_uint32(uint32 k);
/* private routines */
/* hashinsert.c */
extern void _hash_doinsert(Relation rel, IndexTuple itup);
/* hashovfl.c */
extern Buffer _hash_addovflpage(Relation rel, Buffer metabuf, Buffer buf);
extern BlockNumber _hash_freeovflpage(Relation rel, Buffer ovflbuf,
BufferAccessStrategy bstrategy);
extern void _hash_initbitmap(Relation rel, HashMetaPage metap,
BlockNumber blkno);
extern void _hash_squeezebucket(Relation rel,
Bucket bucket, BlockNumber bucket_blkno,
BufferAccessStrategy bstrategy);
/* hashpage.c */
extern void _hash_getlock(Relation rel, BlockNumber whichlock, int access);
extern bool _hash_try_getlock(Relation rel, BlockNumber whichlock, int access);
extern void _hash_droplock(Relation rel, BlockNumber whichlock, int access);
extern Buffer _hash_getbuf(Relation rel, BlockNumber blkno,
int access, int flags);
extern Buffer _hash_getinitbuf(Relation rel, BlockNumber blkno);
extern Buffer _hash_getnewbuf(Relation rel, BlockNumber blkno);
extern Buffer _hash_getbuf_with_strategy(Relation rel, BlockNumber blkno,
int access, int flags,
BufferAccessStrategy bstrategy);
extern void _hash_relbuf(Relation rel, Buffer buf);
extern void _hash_dropbuf(Relation rel, Buffer buf);
extern void _hash_wrtbuf(Relation rel, Buffer buf);
extern void _hash_chgbufaccess(Relation rel, Buffer buf, int from_access,
int to_access);
extern void _hash_metapinit(Relation rel);
extern void _hash_pageinit(Page page, Size size);
extern void _hash_expandtable(Relation rel, Buffer metabuf);
/* hashscan.c */
extern void _hash_regscan(IndexScanDesc scan);
extern void _hash_dropscan(IndexScanDesc scan);
extern bool _hash_has_active_scan(Relation rel, Bucket bucket);
extern void ReleaseResources_hash(void);
/* hashsearch.c */
extern bool _hash_next(IndexScanDesc scan, ScanDirection dir);
extern bool _hash_first(IndexScanDesc scan, ScanDirection dir);
extern bool _hash_step(IndexScanDesc scan, Buffer *bufP, ScanDirection dir);
/* hashutil.c */
extern bool _hash_checkqual(IndexScanDesc scan, IndexTuple itup);
extern uint32 _hash_datum2hashkey(Relation rel, Datum key);
extern uint32 _hash_datum2hashkey_type(Relation rel, Datum key, Oid keytype);
extern Bucket _hash_hashkey2bucket(uint32 hashkey, uint32 maxbucket,
uint32 highmask, uint32 lowmask);
extern uint32 _hash_log2(uint32 num);
extern void _hash_checkpage(Relation rel, Buffer buf, int flags);
/* hash.c */
extern void hash_redo(XLogRecPtr lsn, XLogRecord *record);
extern void hash_desc(StringInfo buf, uint8 xl_info, char *rec);
#endif /* HASH_H */