diff options
Diffstat (limited to 'src/backend/access/nbtree/nbtscan.c')
| -rw-r--r-- | src/backend/access/nbtree/nbtscan.c | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/src/backend/access/nbtree/nbtscan.c b/src/backend/access/nbtree/nbtscan.c new file mode 100644 index 00000000000..62a029bc06f --- /dev/null +++ b/src/backend/access/nbtree/nbtscan.c @@ -0,0 +1,164 @@ +/*------------------------------------------------------------------------- + * + * btscan.c-- + * manage scans on btrees. + * + * Copyright (c) 1994, Regents of the University of California + * + * + * IDENTIFICATION + * $Header: /cvsroot/pgsql/src/backend/access/nbtree/Attic/nbtscan.c,v 1.1.1.1 1996/07/09 06:21:12 scrappy 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. + * + * The scheme is to manage a list of active scans in the current backend. + * Whenever we add or remove records from an index, or whenever we + * split a leaf page, 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 "storage/bufmgr.h" +#include "storage/bufpage.h" + +#include "utils/elog.h" +#include "utils/palloc.h" +#include "utils/rel.h" +#include "utils/excid.h" + +#include "access/heapam.h" +#include "access/genam.h" +#include "access/sdir.h" +#include "access/nbtree.h" + +typedef struct BTScanListData { + IndexScanDesc btsl_scan; + struct BTScanListData *btsl_next; +} BTScanListData; + +typedef BTScanListData *BTScanList; + +static BTScanList BTScans = (BTScanList) NULL; + +/* + * _bt_regscan() -- register a new scan. + */ +void +_bt_regscan(IndexScanDesc scan) +{ + BTScanList new_el; + + new_el = (BTScanList) palloc(sizeof(BTScanListData)); + new_el->btsl_scan = scan; + new_el->btsl_next = BTScans; + BTScans = new_el; +} + +/* + * _bt_dropscan() -- drop a scan from the scan list + */ +void +_bt_dropscan(IndexScanDesc scan) +{ + BTScanList chk, last; + + last = (BTScanList) NULL; + for (chk = BTScans; + chk != (BTScanList) NULL && chk->btsl_scan != scan; + chk = chk->btsl_next) { + last = chk; + } + + if (chk == (BTScanList) NULL) + elog(WARN, "btree scan list trashed; can't find 0x%lx", scan); + + if (last == (BTScanList) NULL) + BTScans = chk->btsl_next; + else + last->btsl_next = chk->btsl_next; + +#ifdef PERFECT_MEM + pfree (chk); +#endif /* PERFECT_MEM */ +} + +void +_bt_adjscans(Relation rel, ItemPointer tid) +{ + BTScanList l; + Oid relid; + + relid = rel->rd_id; + for (l = BTScans; l != (BTScanList) NULL; l = l->btsl_next) { + if (relid == l->btsl_scan->relation->rd_id) + _bt_scandel(l->btsl_scan, ItemPointerGetBlockNumber(tid), + ItemPointerGetOffsetNumber(tid)); + } +} + +void +_bt_scandel(IndexScanDesc scan, BlockNumber blkno, OffsetNumber offno) +{ + ItemPointer current; + Buffer buf; + BTScanOpaque so; + + if (!_bt_scantouched(scan, blkno, offno)) + return; + + so = (BTScanOpaque) scan->opaque; + buf = so->btso_curbuf; + + current = &(scan->currentItemData); + if (ItemPointerIsValid(current) + && ItemPointerGetBlockNumber(current) == blkno + && ItemPointerGetOffsetNumber(current) >= offno) { + _bt_step(scan, &buf, BackwardScanDirection); + so->btso_curbuf = buf; + } + + current = &(scan->currentMarkData); + if (ItemPointerIsValid(current) + && ItemPointerGetBlockNumber(current) == blkno + && ItemPointerGetOffsetNumber(current) >= offno) { + ItemPointerData tmp; + tmp = *current; + *current = scan->currentItemData; + scan->currentItemData = tmp; + _bt_step(scan, &buf, BackwardScanDirection); + so->btso_mrkbuf = buf; + tmp = *current; + *current = scan->currentItemData; + scan->currentItemData = tmp; + } +} + +bool +_bt_scantouched(IndexScanDesc scan, 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); +} |