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 22a7d0ceae6700b71bb65d8f533dedb4ebac1726..9a9927ca05f9764c1fc715efb93def05dbe21350 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 1.69 2008/01/01 19:45:46 momjian Exp $
+ *   $PostgreSQL: pgsql/src/backend/access/gist/gistget.c,v 1.69.2.1 2008/08/23 10:40:03 teodor Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -29,63 +29,39 @@ static bool gistindex_keytest(IndexTuple tuple, IndexScanDesc scan,
 static void
 killtuple(Relation r, GISTScanOpaque so, ItemPointer iptr)
 {
-   Buffer      buffer = so->curbuf;
-
-   for (;;)
-   {
-       Page        p;
-       BlockNumber blkno;
-       OffsetNumber offset,
-                   maxoff;
-
-       LockBuffer(buffer, GIST_SHARE);
-       gistcheckpage(r, buffer);
-       p = (Page) BufferGetPage(buffer);
+   Page        p;
+   OffsetNumber offset;
 
-       if (buffer == so->curbuf && XLByteEQ(so->stack->lsn, PageGetLSN(p)))
-       {
-           /* page unchanged, so all is simple */
-           offset = ItemPointerGetOffsetNumber(iptr);
-           ItemIdMarkDead(PageGetItemId(p, offset));
-           SetBufferCommitInfoNeedsSave(buffer);
-           LockBuffer(buffer, GIST_UNLOCK);
-           break;
-       }
+   LockBuffer(so->curbuf, GIST_SHARE);
+   gistcheckpage(r, so->curbuf);
+   p = (Page) BufferGetPage(so->curbuf);
 
-       maxoff = PageGetMaxOffsetNumber(p);
+   if (XLByteEQ(so->stack->lsn, PageGetLSN(p)))
+   {
+       /* page unchanged, so all is simple */
+       offset = ItemPointerGetOffsetNumber(iptr);
+       ItemIdMarkDead(PageGetItemId(p, offset));
+       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 */
                ItemIdMarkDead(PageGetItemId(p, offset));
-               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);
 }
 
 /*
@@ -147,7 +123,6 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids,
    GISTSearchStack *stk;
    IndexTuple  it;
    GISTPageOpaque opaque;
-   bool        resetoffset = false;
    int         ntids = 0;
 
    so = (GISTScanOpaque) scan->opaque;
@@ -172,6 +147,42 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids,
        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 */
@@ -180,30 +191,25 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids,
        gistcheckpage(scan->indexRelation, so->curbuf);
        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 */
@@ -226,25 +232,13 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids,
            continue;
        }
 
-       if (!GistPageIsLeaf(p) || resetoffset ||
-           !ItemPointerIsValid(&so->curpos))
-       {
-           if (ScanDirectionIsBackward(dir))
-               n = PageGetMaxOffsetNumber(p);
-           else
-               n = FirstOffsetNumber;
-       }
+       if (ScanDirectionIsBackward(dir))
+           n = PageGetMaxOffsetNumber(p);
        else
-       {
-           n = ItemPointerGetOffsetNumber(&(so->curpos));
-
-           if (ScanDirectionIsBackward(dir))
-               n = OffsetNumberPrev(n);
-           else
-               n = OffsetNumberNext(n);
-       }
+           n = FirstOffsetNumber;
 
        /* wonderful, we can look at page */
+       so->nPageData = so->curPageData = 0;
 
        for (;;)
        {
@@ -252,6 +246,20 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids,
 
            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
@@ -292,14 +300,8 @@ gistnext(IndexScanDesc scan, ScanDirection dir, ItemPointer tids,
                if (!(ignore_killed_tuples && ItemIdIsDead(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 187e3bec8324c320a8a1840dba6b1447497789e7..88e1c6ecbee16075f4c083095d5a0c849b177466 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 1.68 2008/01/01 19:45:46 momjian Exp $
+ *   $PostgreSQL: pgsql/src/backend/access/gist/gistscan.c,v 1.68.2.1 2008/08/23 10:40:03 teodor Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -61,6 +61,7 @@ gistrescan(PG_FUNCTION_ARGS)
            ReleaseBuffer(so->markbuf);
            so->markbuf = InvalidBuffer;
        }
+
    }
    else
    {
@@ -81,6 +82,7 @@ gistrescan(PG_FUNCTION_ARGS)
     */
    ItemPointerSetInvalid(&so->curpos);
    ItemPointerSetInvalid(&so->markpos);
+   so->nPageData = so->curPageData = 0;
 
    /* Update scan key, if a new one is given */
    if (key && scan->numberOfKeys > 0)
@@ -148,6 +150,11 @@ 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();
 }
 
@@ -197,6 +204,11 @@ 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 e6ca50a702f26028f9fc2ae87998433a8cbbad38..e823928c3e2ba4d45b9e911e2b1b3daf69391dfb 100644 (file)
--- a/src/include/access/gist_private.h
+++ b/src/include/access/gist_private.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/gist_private.h,v 1.28 2008/01/01 19:45:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/access/gist_private.h,v 1.28.2.1 2008/08/23 10:40:03 teodor Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -75,6 +75,13 @@ typedef struct GISTScanOpaqueData
    ItemPointerData curpos;
    Buffer      markbuf;
    ItemPointerData markpos;
+
+   ItemPointerData pageData[BLCKSZ/sizeof(IndexTupleData)];
+   OffsetNumber    nPageData;
+   OffsetNumber    curPageData;
+   ItemPointerData markPageData[BLCKSZ/sizeof(IndexTupleData)];
+   OffsetNumber    markNPageData;
+   OffsetNumber    markCurPageData;
 } GISTScanOpaqueData;
 
 typedef GISTScanOpaqueData *GISTScanOpaque;