diff options
Diffstat (limited to 'src/backend/access/hash/hashscan.c')
| -rw-r--r-- | src/backend/access/hash/hashscan.c | 229 |
1 files changed, 118 insertions, 111 deletions
diff --git a/src/backend/access/hash/hashscan.c b/src/backend/access/hash/hashscan.c index bd776d68c0..79fa33f747 100644 --- a/src/backend/access/hash/hashscan.c +++ b/src/backend/access/hash/hashscan.c @@ -1,160 +1,167 @@ /*------------------------------------------------------------------------- * * hashscan.c-- - * manage scans on hash tables + * manage scans on hash tables * * Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/access/hash/hashscan.c,v 1.8 1996/11/15 18:36:31 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/access/hash/hashscan.c,v 1.9 1997/09/07 04:38:01 momjian Exp $ * * NOTES - * Because we can be doing an index scan on a relation while we - * update it, we need to avoid missing data that moves around in - * the index. The routines and global variables in this file - * guarantee that all scans in the local address space stay - * correctly positioned. This is all we need to worry about, since - * write locking guarantees that no one else will be on the same - * page at the same time as we are. + * Because we can be doing an index scan on a relation while we + * update it, we need to avoid missing data that moves around in + * the index. The routines and global variables in this file + * guarantee that all scans in the local address space stay + * correctly positioned. This is all we need to worry about, since + * write locking guarantees that no one else will be on the same + * page at the same time as we are. * - * The scheme is to manage a list of active scans in the current - * backend. Whenever we add or remove records from an index, we - * check the list of active scans to see if any has been affected. - * A scan is affected only if it is on the same relation, and the - * same page, as the update. + * The scheme is to manage a list of active scans in the current + * backend. Whenever we add or remove records from an index, we + * check the list of active scans to see if any has been affected. + * A scan is affected only if it is on the same relation, and the + * same page, as the update. * *------------------------------------------------------------------------- */ #include <postgres.h> - + #include <access/hash.h> -static void _hash_scandel(IndexScanDesc scan, BlockNumber blkno, OffsetNumber offno); -static bool _hash_scantouched(IndexScanDesc scan, BlockNumber blkno, OffsetNumber offno); +static void _hash_scandel(IndexScanDesc scan, BlockNumber blkno, OffsetNumber offno); +static bool _hash_scantouched(IndexScanDesc scan, BlockNumber blkno, OffsetNumber offno); -typedef struct HashScanListData { - IndexScanDesc hashsl_scan; - struct HashScanListData *hashsl_next; -} HashScanListData; +typedef struct HashScanListData +{ + IndexScanDesc hashsl_scan; + struct HashScanListData *hashsl_next; +} HashScanListData; -typedef HashScanListData *HashScanList; +typedef HashScanListData *HashScanList; -static HashScanList HashScans = (HashScanList) NULL; +static HashScanList HashScans = (HashScanList) NULL; /* - * _Hash_regscan() -- register a new scan. + * _Hash_regscan() -- register a new scan. */ void _hash_regscan(IndexScanDesc scan) { - HashScanList new_el; - - new_el = (HashScanList) palloc(sizeof(HashScanListData)); - new_el->hashsl_scan = scan; - new_el->hashsl_next = HashScans; - HashScans = new_el; + HashScanList new_el; + + new_el = (HashScanList) palloc(sizeof(HashScanListData)); + new_el->hashsl_scan = scan; + new_el->hashsl_next = HashScans; + HashScans = new_el; } /* - * _hash_dropscan() -- drop a scan from the scan list + * _hash_dropscan() -- drop a scan from the scan list */ void _hash_dropscan(IndexScanDesc scan) { - HashScanList chk, last; - - last = (HashScanList) NULL; - for (chk = HashScans; - chk != (HashScanList) NULL && chk->hashsl_scan != scan; - chk = chk->hashsl_next) { - last = chk; - } - - if (chk == (HashScanList) NULL) - elog(WARN, "hash scan list trashed; can't find 0x%lx", scan); - - if (last == (HashScanList) NULL) - HashScans = chk->hashsl_next; - else - last->hashsl_next = chk->hashsl_next; - - pfree (chk); + HashScanList chk, + last; + + last = (HashScanList) NULL; + for (chk = HashScans; + chk != (HashScanList) NULL && chk->hashsl_scan != scan; + chk = chk->hashsl_next) + { + last = chk; + } + + if (chk == (HashScanList) NULL) + elog(WARN, "hash scan list trashed; can't find 0x%lx", scan); + + if (last == (HashScanList) NULL) + HashScans = chk->hashsl_next; + else + last->hashsl_next = chk->hashsl_next; + + pfree(chk); } void _hash_adjscans(Relation rel, ItemPointer tid) { - HashScanList l; - Oid relid; - - relid = rel->rd_id; - for (l = HashScans; l != (HashScanList) NULL; l = l->hashsl_next) { - if (relid == l->hashsl_scan->relation->rd_id) - _hash_scandel(l->hashsl_scan, ItemPointerGetBlockNumber(tid), - ItemPointerGetOffsetNumber(tid)); - } + HashScanList l; + Oid relid; + + relid = rel->rd_id; + for (l = HashScans; l != (HashScanList) NULL; l = l->hashsl_next) + { + if (relid == l->hashsl_scan->relation->rd_id) + _hash_scandel(l->hashsl_scan, ItemPointerGetBlockNumber(tid), + ItemPointerGetOffsetNumber(tid)); + } } static void _hash_scandel(IndexScanDesc scan, BlockNumber blkno, OffsetNumber offno) { - ItemPointer current; - Buffer buf; - Buffer metabuf; - HashScanOpaque so; - - if (!_hash_scantouched(scan, blkno, offno)) - return; - - metabuf = _hash_getbuf(scan->relation, HASH_METAPAGE, HASH_READ); - - so = (HashScanOpaque) scan->opaque; - buf = so->hashso_curbuf; - - current = &(scan->currentItemData); - if (ItemPointerIsValid(current) - && ItemPointerGetBlockNumber(current) == blkno - && ItemPointerGetOffsetNumber(current) >= offno) { - _hash_step(scan, &buf, BackwardScanDirection, metabuf); - so->hashso_curbuf = buf; - } - - current = &(scan->currentMarkData); - if (ItemPointerIsValid(current) - && ItemPointerGetBlockNumber(current) == blkno - && ItemPointerGetOffsetNumber(current) >= offno) { - ItemPointerData tmp; - tmp = *current; - *current = scan->currentItemData; - scan->currentItemData = tmp; - _hash_step(scan, &buf, BackwardScanDirection, metabuf); - so->hashso_mrkbuf = buf; - tmp = *current; - *current = scan->currentItemData; - scan->currentItemData = tmp; - } + ItemPointer current; + Buffer buf; + Buffer metabuf; + HashScanOpaque so; + + if (!_hash_scantouched(scan, blkno, offno)) + return; + + metabuf = _hash_getbuf(scan->relation, HASH_METAPAGE, HASH_READ); + + so = (HashScanOpaque) scan->opaque; + buf = so->hashso_curbuf; + + current = &(scan->currentItemData); + if (ItemPointerIsValid(current) + && ItemPointerGetBlockNumber(current) == blkno + && ItemPointerGetOffsetNumber(current) >= offno) + { + _hash_step(scan, &buf, BackwardScanDirection, metabuf); + so->hashso_curbuf = buf; + } + + current = &(scan->currentMarkData); + if (ItemPointerIsValid(current) + && ItemPointerGetBlockNumber(current) == blkno + && ItemPointerGetOffsetNumber(current) >= offno) + { + ItemPointerData tmp; + + tmp = *current; + *current = scan->currentItemData; + scan->currentItemData = tmp; + _hash_step(scan, &buf, BackwardScanDirection, metabuf); + so->hashso_mrkbuf = buf; + tmp = *current; + *current = scan->currentItemData; + scan->currentItemData = tmp; + } } -static bool +static bool _hash_scantouched(IndexScanDesc scan, - BlockNumber blkno, - OffsetNumber offno) + BlockNumber blkno, + OffsetNumber offno) { - ItemPointer current; - - current = &(scan->currentItemData); - if (ItemPointerIsValid(current) - && ItemPointerGetBlockNumber(current) == blkno - && ItemPointerGetOffsetNumber(current) >= offno) - return (true); - - current = &(scan->currentMarkData); - if (ItemPointerIsValid(current) - && ItemPointerGetBlockNumber(current) == blkno - && ItemPointerGetOffsetNumber(current) >= offno) - return (true); - - return (false); + ItemPointer current; + + current = &(scan->currentItemData); + if (ItemPointerIsValid(current) + && ItemPointerGetBlockNumber(current) == blkno + && ItemPointerGetOffsetNumber(current) >= offno) + return (true); + + current = &(scan->currentMarkData); + if (ItemPointerIsValid(current) + && ItemPointerGetBlockNumber(current) == blkno + && ItemPointerGetOffsetNumber(current) >= offno) + return (true); + + return (false); } |