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Postgres95 1.01 Distribution - Virgin Sources
This commit is contained in:
Marc G. Fournier
320
src/backend/access/rtree/rtget.c
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320
src/backend/access/rtree/rtget.c
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/*-------------------------------------------------------------------------
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*
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* rtget.c--
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* fetch tuples from an rtree scan.
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*
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* Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/access/rtree/Attic/rtget.c,v 1.1.1.1 1996/07/09 06:21:13 scrappy Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "storage/bufmgr.h"
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#include "storage/bufpage.h"
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#include "utils/elog.h"
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#include "utils/palloc.h"
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#include "utils/rel.h"
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#include "access/heapam.h"
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#include "access/genam.h"
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#include "access/iqual.h"
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#include "access/rtree.h"
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#include "access/sdir.h"
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static OffsetNumber findnext(IndexScanDesc s, Page p, OffsetNumber n,
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ScanDirection dir);
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static RetrieveIndexResult rtscancache(IndexScanDesc s, ScanDirection dir);
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static RetrieveIndexResult rtfirst(IndexScanDesc s, ScanDirection dir);
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static RetrieveIndexResult rtnext(IndexScanDesc s, ScanDirection dir);
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static ItemPointer rtheapptr(Relation r, ItemPointer itemp);
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RetrieveIndexResult
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rtgettuple(IndexScanDesc s, ScanDirection dir)
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{
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RetrieveIndexResult res;
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/* if we have it cached in the scan desc, just return the value */
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if ((res = rtscancache(s, dir)) != (RetrieveIndexResult) NULL)
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return (res);
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/* not cached, so we'll have to do some work */
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if (ItemPointerIsValid(&(s->currentItemData))) {
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res = rtnext(s, dir);
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} else {
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res = rtfirst(s, dir);
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}
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return (res);
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}
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static RetrieveIndexResult
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rtfirst(IndexScanDesc s, ScanDirection dir)
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{
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Buffer b;
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Page p;
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OffsetNumber n;
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OffsetNumber maxoff;
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RetrieveIndexResult res;
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RTreePageOpaque po;
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RTreeScanOpaque so;
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RTSTACK *stk;
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BlockNumber blk;
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IndexTuple it;
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ItemPointer ip;
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b = ReadBuffer(s->relation, P_ROOT);
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p = BufferGetPage(b);
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po = (RTreePageOpaque) PageGetSpecialPointer(p);
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so = (RTreeScanOpaque) s->opaque;
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for (;;) {
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maxoff = PageGetMaxOffsetNumber(p);
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if (ScanDirectionIsBackward(dir))
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n = findnext(s, p, maxoff, dir);
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else
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n = findnext(s, p, FirstOffsetNumber, dir);
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while (n < FirstOffsetNumber || n > maxoff) {
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ReleaseBuffer(b);
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if (so->s_stack == (RTSTACK *) NULL)
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return ((RetrieveIndexResult) NULL);
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stk = so->s_stack;
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b = ReadBuffer(s->relation, stk->rts_blk);
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p = BufferGetPage(b);
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po = (RTreePageOpaque) PageGetSpecialPointer(p);
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maxoff = PageGetMaxOffsetNumber(p);
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if (ScanDirectionIsBackward(dir)) {
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n = OffsetNumberPrev(stk->rts_child);
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} else {
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n = OffsetNumberNext(stk->rts_child);
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}
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so->s_stack = stk->rts_parent;
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pfree(stk);
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n = findnext(s, p, n, dir);
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}
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if (po->flags & F_LEAF) {
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ItemPointerSet(&(s->currentItemData), BufferGetBlockNumber(b), n);
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it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
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ip = (ItemPointer) palloc(sizeof(ItemPointerData));
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memmove((char *) ip, (char *) &(it->t_tid),
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sizeof(ItemPointerData));
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ReleaseBuffer(b);
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res = FormRetrieveIndexResult(&(s->currentItemData), ip);
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return (res);
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} else {
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stk = (RTSTACK *) palloc(sizeof(RTSTACK));
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stk->rts_child = n;
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stk->rts_blk = BufferGetBlockNumber(b);
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stk->rts_parent = so->s_stack;
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so->s_stack = stk;
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it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
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blk = ItemPointerGetBlockNumber(&(it->t_tid));
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ReleaseBuffer(b);
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b = ReadBuffer(s->relation, blk);
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p = BufferGetPage(b);
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po = (RTreePageOpaque) PageGetSpecialPointer(p);
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}
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}
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}
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static RetrieveIndexResult
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rtnext(IndexScanDesc s, ScanDirection dir)
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{
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Buffer b;
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Page p;
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OffsetNumber n;
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OffsetNumber maxoff;
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RetrieveIndexResult res;
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RTreePageOpaque po;
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RTreeScanOpaque so;
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RTSTACK *stk;
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BlockNumber blk;
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IndexTuple it;
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ItemPointer ip;
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blk = ItemPointerGetBlockNumber(&(s->currentItemData));
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n = ItemPointerGetOffsetNumber(&(s->currentItemData));
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if (ScanDirectionIsForward(dir)) {
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n = OffsetNumberNext(n);
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} else {
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n = OffsetNumberPrev(n);
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}
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b = ReadBuffer(s->relation, blk);
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p = BufferGetPage(b);
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po = (RTreePageOpaque) PageGetSpecialPointer(p);
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so = (RTreeScanOpaque) s->opaque;
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for (;;) {
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maxoff = PageGetMaxOffsetNumber(p);
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n = findnext(s, p, n, dir);
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while (n < FirstOffsetNumber || n > maxoff) {
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ReleaseBuffer(b);
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if (so->s_stack == (RTSTACK *) NULL)
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return ((RetrieveIndexResult) NULL);
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stk = so->s_stack;
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b = ReadBuffer(s->relation, stk->rts_blk);
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p = BufferGetPage(b);
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maxoff = PageGetMaxOffsetNumber(p);
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po = (RTreePageOpaque) PageGetSpecialPointer(p);
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if (ScanDirectionIsBackward(dir)) {
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n = OffsetNumberPrev(stk->rts_child);
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} else {
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n = OffsetNumberNext(stk->rts_child);
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}
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so->s_stack = stk->rts_parent;
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pfree(stk);
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n = findnext(s, p, n, dir);
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}
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if (po->flags & F_LEAF) {
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ItemPointerSet(&(s->currentItemData), BufferGetBlockNumber(b), n);
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it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
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ip = (ItemPointer) palloc(sizeof(ItemPointerData));
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memmove((char *) ip, (char *) &(it->t_tid),
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sizeof(ItemPointerData));
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ReleaseBuffer(b);
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res = FormRetrieveIndexResult(&(s->currentItemData), ip);
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return (res);
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} else {
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stk = (RTSTACK *) palloc(sizeof(RTSTACK));
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stk->rts_child = n;
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stk->rts_blk = BufferGetBlockNumber(b);
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stk->rts_parent = so->s_stack;
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so->s_stack = stk;
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it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
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blk = ItemPointerGetBlockNumber(&(it->t_tid));
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ReleaseBuffer(b);
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b = ReadBuffer(s->relation, blk);
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p = BufferGetPage(b);
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po = (RTreePageOpaque) PageGetSpecialPointer(p);
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if (ScanDirectionIsBackward(dir)) {
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n = PageGetMaxOffsetNumber(p);
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} else {
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n = FirstOffsetNumber;
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}
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}
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}
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}
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static OffsetNumber
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findnext(IndexScanDesc s, Page p, OffsetNumber n, ScanDirection dir)
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{
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OffsetNumber maxoff;
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IndexTuple it;
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RTreePageOpaque po;
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RTreeScanOpaque so;
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maxoff = PageGetMaxOffsetNumber(p);
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po = (RTreePageOpaque) PageGetSpecialPointer(p);
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so = (RTreeScanOpaque) s->opaque;
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/*
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* If we modified the index during the scan, we may have a pointer to
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* a ghost tuple, before the scan. If this is the case, back up one.
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*/
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if (so->s_flags & RTS_CURBEFORE) {
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so->s_flags &= ~RTS_CURBEFORE;
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n = OffsetNumberPrev(n);
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}
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while (n >= FirstOffsetNumber && n <= maxoff) {
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it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
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if (po->flags & F_LEAF) {
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if (index_keytest(it,
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RelationGetTupleDescriptor(s->relation),
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s->numberOfKeys, s->keyData))
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break;
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} else {
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if (index_keytest(it,
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RelationGetTupleDescriptor(s->relation),
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so->s_internalNKey, so->s_internalKey))
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break;
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}
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if (ScanDirectionIsBackward(dir)) {
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n = OffsetNumberPrev(n);
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} else {
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n = OffsetNumberNext(n);
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}
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}
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return (n);
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}
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static RetrieveIndexResult
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rtscancache(IndexScanDesc s, ScanDirection dir)
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{
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RetrieveIndexResult res;
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ItemPointer ip;
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if (!(ScanDirectionIsNoMovement(dir)
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&& ItemPointerIsValid(&(s->currentItemData)))) {
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return ((RetrieveIndexResult) NULL);
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}
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ip = rtheapptr(s->relation, &(s->currentItemData));
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if (ItemPointerIsValid(ip))
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res = FormRetrieveIndexResult(&(s->currentItemData), ip);
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else
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res = (RetrieveIndexResult) NULL;
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return (res);
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}
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/*
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* rtheapptr returns the item pointer to the tuple in the heap relation
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* for which itemp is the index relation item pointer.
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*/
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static ItemPointer
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rtheapptr(Relation r, ItemPointer itemp)
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{
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Buffer b;
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Page p;
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IndexTuple it;
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ItemPointer ip;
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OffsetNumber n;
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ip = (ItemPointer) palloc(sizeof(ItemPointerData));
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if (ItemPointerIsValid(itemp)) {
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b = ReadBuffer(r, ItemPointerGetBlockNumber(itemp));
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p = BufferGetPage(b);
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n = ItemPointerGetOffsetNumber(itemp);
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it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
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memmove((char *) ip, (char *) &(it->t_tid),
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sizeof(ItemPointerData));
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ReleaseBuffer(b);
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} else {
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ItemPointerSetInvalid(ip);
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}
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return (ip);
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}
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