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Diffstat (limited to 'src/backend/access/nbtree/nbtree.c')
-rw-r--r--src/backend/access/nbtree/nbtree.c129
1 files changed, 55 insertions, 74 deletions
diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index b174d303176..072d4000705 100644
--- a/src/backend/access/nbtree/nbtree.c
+++ b/src/backend/access/nbtree/nbtree.c
@@ -12,7 +12,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtree.c,v 1.61 2000/07/14 22:17:33 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtree.c,v 1.62 2000/07/21 06:42:32 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -26,6 +26,7 @@
#include "executor/executor.h"
#include "miscadmin.h"
+
bool BuildingBtree = false; /* see comment in btbuild() */
bool FastBuild = true; /* use sort/build instead of insertion
* build */
@@ -206,8 +207,8 @@ btbuild(PG_FUNCTION_ARGS)
* btree pages - NULLs greater NOT_NULLs and NULL = NULL is TRUE.
* Sure, it's just rule for placing/finding items and no more -
* keytest'll return FALSE for a = 5 for items having 'a' isNULL.
- * Look at _bt_skeycmp, _bt_compare and _bt_itemcmp for how it
- * works. - vadim 03/23/97
+ * Look at _bt_compare for how it works.
+ * - vadim 03/23/97
*
* if (itup->t_info & INDEX_NULL_MASK) { pfree(itup); continue; }
*/
@@ -321,14 +322,6 @@ btinsert(PG_FUNCTION_ARGS)
/* generate an index tuple */
itup = index_formtuple(RelationGetDescr(rel), datum, nulls);
itup->t_tid = *ht_ctid;
-
- /*
- * See comments in btbuild.
- *
- * if (itup->t_info & INDEX_NULL_MASK)
- * PG_RETURN_POINTER((InsertIndexResult) NULL);
- */
-
btitem = _bt_formitem(itup);
res = _bt_doinsert(rel, btitem, rel->rd_uniqueindex, heapRel);
@@ -357,10 +350,10 @@ btgettuple(PG_FUNCTION_ARGS)
if (ItemPointerIsValid(&(scan->currentItemData)))
{
-
/*
* Restore scan position using heap TID returned by previous call
- * to btgettuple(). _bt_restscan() locks buffer.
+ * to btgettuple(). _bt_restscan() re-grabs the read lock on
+ * the buffer, too.
*/
_bt_restscan(scan);
res = _bt_next(scan, dir);
@@ -369,8 +362,9 @@ btgettuple(PG_FUNCTION_ARGS)
res = _bt_first(scan, dir);
/*
- * Save heap TID to use it in _bt_restscan. Unlock buffer before
- * leaving index !
+ * Save heap TID to use it in _bt_restscan. Then release the read
+ * lock on the buffer so that we aren't blocking other backends.
+ * NOTE: we do keep the pin on the buffer!
*/
if (res)
{
@@ -419,7 +413,18 @@ btrescan(PG_FUNCTION_ARGS)
so = (BTScanOpaque) scan->opaque;
- /* we don't hold a read lock on the current page in the scan */
+ if (so == NULL) /* if called from btbeginscan */
+ {
+ so = (BTScanOpaque) palloc(sizeof(BTScanOpaqueData));
+ so->btso_curbuf = so->btso_mrkbuf = InvalidBuffer;
+ so->keyData = (ScanKey) NULL;
+ if (scan->numberOfKeys > 0)
+ so->keyData = (ScanKey) palloc(scan->numberOfKeys * sizeof(ScanKeyData));
+ scan->opaque = so;
+ scan->flags = 0x0;
+ }
+
+ /* we aren't holding any read locks, but gotta drop the pins */
if (ItemPointerIsValid(iptr = &(scan->currentItemData)))
{
ReleaseBuffer(so->btso_curbuf);
@@ -427,7 +432,6 @@ btrescan(PG_FUNCTION_ARGS)
ItemPointerSetInvalid(iptr);
}
- /* and we don't hold a read lock on the last marked item in the scan */
if (ItemPointerIsValid(iptr = &(scan->currentMarkData)))
{
ReleaseBuffer(so->btso_mrkbuf);
@@ -435,17 +439,6 @@ btrescan(PG_FUNCTION_ARGS)
ItemPointerSetInvalid(iptr);
}
- if (so == NULL) /* if called from btbeginscan */
- {
- so = (BTScanOpaque) palloc(sizeof(BTScanOpaqueData));
- so->btso_curbuf = so->btso_mrkbuf = InvalidBuffer;
- so->keyData = (ScanKey) NULL;
- if (scan->numberOfKeys > 0)
- so->keyData = (ScanKey) palloc(scan->numberOfKeys * sizeof(ScanKeyData));
- scan->opaque = so;
- scan->flags = 0x0;
- }
-
/*
* Reset the scan keys. Note that keys ordering stuff moved to
* _bt_first. - vadim 05/05/97
@@ -472,7 +465,7 @@ btmovescan(IndexScanDesc scan, Datum v)
so = (BTScanOpaque) scan->opaque;
- /* we don't hold a read lock on the current page in the scan */
+ /* we aren't holding any read locks, but gotta drop the pin */
if (ItemPointerIsValid(iptr = &(scan->currentItemData)))
{
ReleaseBuffer(so->btso_curbuf);
@@ -480,7 +473,6 @@ btmovescan(IndexScanDesc scan, Datum v)
ItemPointerSetInvalid(iptr);
}
-/* scan->keyData[0].sk_argument = v; */
so->keyData[0].sk_argument = v;
}
@@ -496,7 +488,7 @@ btendscan(PG_FUNCTION_ARGS)
so = (BTScanOpaque) scan->opaque;
- /* we don't hold any read locks */
+ /* we aren't holding any read locks, but gotta drop the pins */
if (ItemPointerIsValid(iptr = &(scan->currentItemData)))
{
if (BufferIsValid(so->btso_curbuf))
@@ -534,7 +526,7 @@ btmarkpos(PG_FUNCTION_ARGS)
so = (BTScanOpaque) scan->opaque;
- /* we don't hold any read locks */
+ /* we aren't holding any read locks, but gotta drop the pin */
if (ItemPointerIsValid(iptr = &(scan->currentMarkData)))
{
ReleaseBuffer(so->btso_mrkbuf);
@@ -542,7 +534,7 @@ btmarkpos(PG_FUNCTION_ARGS)
ItemPointerSetInvalid(iptr);
}
- /* bump pin on current buffer */
+ /* bump pin on current buffer for assignment to mark buffer */
if (ItemPointerIsValid(&(scan->currentItemData)))
{
so->btso_mrkbuf = ReadBuffer(scan->relation,
@@ -566,7 +558,7 @@ btrestrpos(PG_FUNCTION_ARGS)
so = (BTScanOpaque) scan->opaque;
- /* we don't hold any read locks */
+ /* we aren't holding any read locks, but gotta drop the pin */
if (ItemPointerIsValid(iptr = &(scan->currentItemData)))
{
ReleaseBuffer(so->btso_curbuf);
@@ -579,7 +571,6 @@ btrestrpos(PG_FUNCTION_ARGS)
{
so->btso_curbuf = ReadBuffer(scan->relation,
BufferGetBlockNumber(so->btso_mrkbuf));
-
scan->currentItemData = scan->currentMarkData;
so->curHeapIptr = so->mrkHeapIptr;
}
@@ -603,6 +594,9 @@ btdelete(PG_FUNCTION_ARGS)
PG_RETURN_VOID();
}
+/*
+ * Restore scan position when btgettuple is called to continue a scan.
+ */
static void
_bt_restscan(IndexScanDesc scan)
{
@@ -618,7 +612,12 @@ _bt_restscan(IndexScanDesc scan)
BTItem item;
BlockNumber blkno;
- LockBuffer(buf, BT_READ); /* lock buffer first! */
+ /*
+ * Get back the read lock we were holding on the buffer.
+ * (We still have a reference-count pin on it, though.)
+ */
+ LockBuffer(buf, BT_READ);
+
page = BufferGetPage(buf);
maxoff = PageGetMaxOffsetNumber(page);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
@@ -631,43 +630,40 @@ _bt_restscan(IndexScanDesc scan)
*/
if (!ItemPointerIsValid(&target))
{
- ItemPointerSetOffsetNumber(&(scan->currentItemData),
- OffsetNumberPrev(P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY));
+ ItemPointerSetOffsetNumber(current,
+ OffsetNumberPrev(P_FIRSTDATAKEY(opaque)));
return;
}
- if (maxoff >= offnum)
+ /*
+ * The item we were on may have moved right due to insertions.
+ * Find it again.
+ */
+ for (;;)
{
-
- /*
- * if the item is where we left it or has just moved right on this
- * page, we're done
- */
+ /* Check for item on this page */
for (;
offnum <= maxoff;
offnum = OffsetNumberNext(offnum))
{
item = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
- if (item->bti_itup.t_tid.ip_blkid.bi_hi == \
- target.ip_blkid.bi_hi && \
- item->bti_itup.t_tid.ip_blkid.bi_lo == \
- target.ip_blkid.bi_lo && \
+ if (item->bti_itup.t_tid.ip_blkid.bi_hi ==
+ target.ip_blkid.bi_hi &&
+ item->bti_itup.t_tid.ip_blkid.bi_lo ==
+ target.ip_blkid.bi_lo &&
item->bti_itup.t_tid.ip_posid == target.ip_posid)
{
current->ip_posid = offnum;
return;
}
}
- }
- /*
- * By here, the item we're looking for moved right at least one page
- */
- for (;;)
- {
+ /*
+ * By here, the item we're looking for moved right at least one page
+ */
if (P_RIGHTMOST(opaque))
- elog(FATAL, "_bt_restscan: my bits moved right off the end of the world!\
-\n\tRecreate index %s.", RelationGetRelationName(rel));
+ elog(FATAL, "_bt_restscan: my bits moved right off the end of the world!"
+ "\n\tRecreate index %s.", RelationGetRelationName(rel));
blkno = opaque->btpo_next;
_bt_relbuf(rel, buf, BT_READ);
@@ -675,23 +671,8 @@ _bt_restscan(IndexScanDesc scan)
page = BufferGetPage(buf);
maxoff = PageGetMaxOffsetNumber(page);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
-
- /* see if it's on this page */
- for (offnum = P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY;
- offnum <= maxoff;
- offnum = OffsetNumberNext(offnum))
- {
- item = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
- if (item->bti_itup.t_tid.ip_blkid.bi_hi == \
- target.ip_blkid.bi_hi && \
- item->bti_itup.t_tid.ip_blkid.bi_lo == \
- target.ip_blkid.bi_lo && \
- item->bti_itup.t_tid.ip_posid == target.ip_posid)
- {
- ItemPointerSet(current, blkno, offnum);
- so->btso_curbuf = buf;
- return;
- }
- }
+ offnum = P_FIRSTDATAKEY(opaque);
+ ItemPointerSet(current, blkno, offnum);
+ so->btso_curbuf = buf;
}
}
generated by cgit v1.2.3 (git 2.25.1) at 2025-06-02 04:54:22 +0000