Fix possible duplicate tuples while GiST scan. Now page is processed

at once and ItemPointers are collected in memory.

Remove tuple's killing by killtuple() if tuple was moved to another
page - it could produce unaceptable overhead.

Backpatch up to 8.1 because the bug was introduced by GiST's concurrency support.

diff --git a/src/backend/access/gist/gistget.c b/src/backend/access/gist/gistget.c
index 1e02ec082f4f0f559367722eda599520b60348c3..feeb84d38d73ff1c29b94671e0e6b7263c38606e 100644 (file)
--- a/src/backend/access/gist/gistget.c
+++ b/src/backend/access/gist/gistget.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/access/gist/gistget.c,v 1.52.2.1 2005/11/22 18:23:03 momjian Exp $
+ *       $PostgreSQL: pgsql/src/backend/access/gist/gistget.c,v 1.52.2.2 2008/08/23 10:43:58 teodor Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -30,62 +30,38 @@ static bool gistindex_keytest(IndexTuple tuple, IndexScanDesc scan,
 static void
 killtuple(Relation r, GISTScanOpaque so, ItemPointer iptr)
 {
-       Buffer          buffer = so->curbuf;
+       Page        p;
+       OffsetNumber offset;
 
-       for (;;)
+       LockBuffer(so->curbuf, GIST_SHARE);
+       p = (Page) BufferGetPage(so->curbuf);
+ 
+       if (XLByteEQ(so->stack->lsn, PageGetLSN(p)))
        {
-               Page            p;
-               BlockNumber blkno;
-               OffsetNumber offset,
-                                       maxoff;
-
-               LockBuffer(buffer, GIST_SHARE);
-               p = (Page) BufferGetPage(buffer);
-
-               if (buffer == so->curbuf && XLByteEQ(so->stack->lsn, PageGetLSN(p)))
-               {
-                       /* page unchanged, so all is simple */
-                       offset = ItemPointerGetOffsetNumber(iptr);
-                       PageGetItemId(p, offset)->lp_flags |= LP_DELETE;
-                       SetBufferCommitInfoNeedsSave(buffer);
-                       LockBuffer(buffer, GIST_UNLOCK);
-                       break;
-               }
-
-               maxoff = PageGetMaxOffsetNumber(p);
+               /* page unchanged, so all is simple */
+               offset = ItemPointerGetOffsetNumber(iptr);
+               PageGetItemId(p, offset)->lp_flags |= LP_DELETE;
+               SetBufferCommitInfoNeedsSave(so->curbuf);
+       }
+       else
+       {
+               OffsetNumber maxoff = PageGetMaxOffsetNumber(p);
 
                for (offset = FirstOffsetNumber; offset <= maxoff; offset = OffsetNumberNext(offset))
                {
-                       IndexTuple      ituple = (IndexTuple) PageGetItem(p, PageGetItemId(p, offset));
+                       IndexTuple  ituple = (IndexTuple) PageGetItem(p, PageGetItemId(p, offset));
 
                        if (ItemPointerEquals(&(ituple->t_tid), iptr))
                        {
                                /* found */
                                PageGetItemId(p, offset)->lp_flags |= LP_DELETE;
-                               SetBufferCommitInfoNeedsSave(buffer);
-                               LockBuffer(buffer, GIST_UNLOCK);
-                               if (buffer != so->curbuf)
-                                       ReleaseBuffer(buffer);
-                               return;
+                               SetBufferCommitInfoNeedsSave(so->curbuf);
+                               break;
                        }
                }
-
-               /* follow right link */
-
-               /*
-                * ??? is it good? if tuple dropped by concurrent vacuum, we will read
-                * all leaf pages...
-                */
-               blkno = GistPageGetOpaque(p)->rightlink;
-               LockBuffer(buffer, GIST_UNLOCK);
-               if (buffer != so->curbuf)
-                       ReleaseBuffer(buffer);
-
-               if (blkno == InvalidBlockNumber)
-                       /* can't found, dropped by somebody else */
-                       return;
-               buffer = ReadBuffer(r, blkno);
        }
+
+       LockBuffer(so->curbuf, GIST_UNLOCK);
 }
 
 /*
@@ -146,7 +122,6 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids, int maxtids, b
        GISTSearchStack *stk;
        IndexTuple      it;
        GISTPageOpaque opaque;
-       bool            resetoffset = false;
        int                     ntids = 0;
 
        so = (GISTScanOpaque) scan->opaque;
@@ -171,6 +146,42 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids, int maxtids, b
                return 0;
        }
 
+       /*
+        * check stored pointers from last visit 
+        */
+       if ( so->nPageData > 0 ) 
+       {
+               while( ntids < maxtids && so->curPageData < so->nPageData )
+               {
+                       tids[ ntids ] = scan->xs_ctup.t_self = so->pageData[ so->curPageData ];
+                               
+                       so->curPageData ++;
+                       ntids++;
+               }
+
+               if ( ntids == maxtids )
+                       return ntids;
+               
+               /*
+                * Go to the next page
+                */
+               stk = so->stack->next;
+               pfree(so->stack);
+               so->stack = stk;
+
+               /* If we're out of stack entries, we're done */
+               if (so->stack == NULL)
+               {
+                       ReleaseBuffer(so->curbuf);
+                       so->curbuf = InvalidBuffer;
+                       return ntids;
+               }
+
+               so->curbuf = ReleaseAndReadBuffer(so->curbuf,
+                                                                                 scan->indexRelation,
+                                                                                 stk->block);
+       }
+
        for (;;)
        {
                /* First of all, we need lock buffer */
@@ -178,30 +189,25 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids, int maxtids, b
                LockBuffer(so->curbuf, GIST_SHARE);
                p = BufferGetPage(so->curbuf);
                opaque = GistPageGetOpaque(p);
-               resetoffset = false;
 
-               if (XLogRecPtrIsInvalid(so->stack->lsn) || !XLByteEQ(so->stack->lsn, PageGetLSN(p)))
-               {
-                       /* page changed from last visit or visit first time , reset offset */
-                       so->stack->lsn = PageGetLSN(p);
-                       resetoffset = true;
-
-                       /* check page split, occured from last visit or visit to parent */
-                       if (!XLogRecPtrIsInvalid(so->stack->parentlsn) &&
-                               XLByteLT(so->stack->parentlsn, opaque->nsn) &&
-                               opaque->rightlink != InvalidBlockNumber /* sanity check */ &&
-                               (so->stack->next == NULL || so->stack->next->block != opaque->rightlink)                /* check if already
-                                       added */ )
-                       {
-                               /* detect page split, follow right link to add pages */
+               /* remember lsn to identify page changed for tuple's killing */
+               so->stack->lsn = PageGetLSN(p);
 
-                               stk = (GISTSearchStack *) palloc(sizeof(GISTSearchStack));
-                               stk->next = so->stack->next;
-                               stk->block = opaque->rightlink;
-                               stk->parentlsn = so->stack->parentlsn;
-                               memset(&(stk->lsn), 0, sizeof(GistNSN));
-                               so->stack->next = stk;
-                       }
+               /* check page split, occured from last visit or visit to parent */
+               if (!XLogRecPtrIsInvalid(so->stack->parentlsn) &&
+                       XLByteLT(so->stack->parentlsn, opaque->nsn) &&
+                       opaque->rightlink != InvalidBlockNumber /* sanity check */ &&
+                       (so->stack->next == NULL || so->stack->next->block != opaque->rightlink)                /* check if already
+                                       added */ )
+               {
+                       /* detect page split, follow right link to add pages */
+
+                       stk = (GISTSearchStack *) palloc(sizeof(GISTSearchStack));
+                       stk->next = so->stack->next;
+                       stk->block = opaque->rightlink;
+                       stk->parentlsn = so->stack->parentlsn;
+                       memset(&(stk->lsn), 0, sizeof(GistNSN));
+                       so->stack->next = stk;
                }
 
                /* if page is empty, then just skip it */
@@ -224,24 +230,13 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids, int maxtids, b
                        continue;
                }
 
-               if (!GistPageIsLeaf(p) || resetoffset || ItemPointerIsValid(&scan->currentItemData) == false)
-               {
-                       if (ScanDirectionIsBackward(dir))
-                               n = PageGetMaxOffsetNumber(p);
-                       else
-                               n = FirstOffsetNumber;
-               }
+               if (ScanDirectionIsBackward(dir))
+                       n = PageGetMaxOffsetNumber(p);
                else
-               {
-                       n = ItemPointerGetOffsetNumber(&(scan->currentItemData));
-
-                       if (ScanDirectionIsBackward(dir))
-                               n = OffsetNumberPrev(n);
-                       else
-                               n = OffsetNumberNext(n);
-               }
+                       n = FirstOffsetNumber;
 
                /* wonderfull, we can look at page */
+               so->nPageData = so->curPageData = 0;
 
                for (;;)
                {
@@ -249,6 +244,20 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids, int maxtids, b
 
                        if (!OffsetNumberIsValid(n))
                        {
+                               while( ntids < maxtids && so->curPageData < so->nPageData )
+                               {
+                                       tids[ ntids ] = scan->xs_ctup.t_self = so->pageData[ so->curPageData ];
+                               
+                                       so->curPageData ++;
+                                       ntids++;
+                               }
+
+                               if ( ntids == maxtids )
+                               {
+                                       LockBuffer(so->curbuf, GIST_UNLOCK);
+                                       return ntids;
+                               }
+
                                /*
                                 * We ran out of matching index entries on the current page,
                                 * so pop the top stack entry and use it to continue the
@@ -288,14 +297,8 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids, int maxtids, b
                                if (!(ignore_killed_tuples && ItemIdDeleted(PageGetItemId(p, n))))
                                {
                                        it = (IndexTuple) PageGetItem(p, PageGetItemId(p, n));
-                                       tids[ntids] = scan->xs_ctup.t_self = it->t_tid;
-                                       ntids++;
-
-                                       if (ntids == maxtids)
-                                       {
-                                               LockBuffer(so->curbuf, GIST_UNLOCK);
-                                               return ntids;
-                                       }
+                                       so->pageData[ so->nPageData ] = it->t_tid;
+                                       so->nPageData ++;
                                }
                        }
                        else

diff --git a/src/backend/access/gist/gistscan.c b/src/backend/access/gist/gistscan.c
index 97f4d264d1a57e404aa89ccb246a7f512013f927..3604debba0f4e2514812f244f175e0244c61b3a8 100644 (file)
--- a/src/backend/access/gist/gistscan.c
+++ b/src/backend/access/gist/gistscan.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/access/gist/gistscan.c,v 1.61 2005/09/22 20:44:36 momjian Exp $
+ *       $PostgreSQL: pgsql/src/backend/access/gist/gistscan.c,v 1.61.2.1 2008/08/23 10:43:58 teodor Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -98,6 +98,7 @@ gistrescan(PG_FUNCTION_ARGS)
                        ReleaseBuffer(so->markbuf);
                        so->markbuf = InvalidBuffer;
                }
+
        }
        else
        {
@@ -113,6 +114,8 @@ gistrescan(PG_FUNCTION_ARGS)
                scan->opaque = so;
        }
 
+       so->nPageData = so->curPageData = 0;
+
        /* Update scan key, if a new one is given */
        if (key && scan->numberOfKeys > 0)
        {
@@ -179,6 +182,11 @@ gistmarkpos(PG_FUNCTION_ARGS)
                so->markbuf = so->curbuf;
        }
 
+       so->markNPageData = so->nPageData;
+       so->markCurPageData = so->curPageData;
+       if ( so->markNPageData > 0 )
+               memcpy( so->markPageData, so->pageData, sizeof(ItemPointerData) * so->markNPageData );          
+
        PG_RETURN_VOID();
 }
 
@@ -228,6 +236,11 @@ gistrestrpos(PG_FUNCTION_ARGS)
                so->curbuf = so->markbuf;
        }
 
+       so->nPageData = so->markNPageData;
+       so->curPageData = so->markNPageData;
+       if ( so->markNPageData > 0 )
+               memcpy( so->pageData, so->markPageData, sizeof(ItemPointerData) * so->markNPageData );          
+
        PG_RETURN_VOID();
 }
 

diff --git a/src/include/access/gist_private.h b/src/include/access/gist_private.h
index 1cfa5b92bc2c1fdb12c123855b4ed6dbeaed03ec..c1861180d24a93030ec96cbdc81909c2cb212e77 100644 (file)
--- a/src/include/access/gist_private.h
+++ b/src/include/access/gist_private.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/gist_private.h,v 1.8 2005/10/15 02:49:42 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/access/gist_private.h,v 1.8.2.1 2008/08/23 10:43:58 teodor Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -73,6 +73,13 @@ typedef struct GISTScanOpaqueData
        MemoryContext tempCxt;
        Buffer          curbuf;
        Buffer          markbuf;
+
+       ItemPointerData pageData[BLCKSZ/sizeof(IndexTupleData)];
+       OffsetNumber    nPageData;
+       OffsetNumber    curPageData;
+       ItemPointerData markPageData[BLCKSZ/sizeof(IndexTupleData)];
+       OffsetNumber    markNPageData;
+       OffsetNumber    markCurPageData;
 } GISTScanOpaqueData;
 
 typedef GISTScanOpaqueData *GISTScanOpaque;