Concurrency... Highest one...

DO NOT EVEN TRY TO DO PageGetMaxOffsetNumber BEFORE
LockBuffer!
-:)

diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index 4b472d0c5e51be7903ec9a5f3961ed8223382275..aa0b94ea8f8ab1e990579c3681b2b27a266e73ce 100644 (file)
--- a/src/backend/access/nbtree/nbtree.c
+++ b/src/backend/access/nbtree/nbtree.c
@@ -618,16 +618,19 @@ _bt_restscan(IndexScanDesc scan)
        Relation        rel = scan->relation;
        BTScanOpaque so = (BTScanOpaque) scan->opaque;
        Buffer          buf = so->btso_curbuf;
-       Page            page = BufferGetPage(buf);
+       Page            page;
        ItemPointer current = &(scan->currentItemData);
        OffsetNumber offnum = ItemPointerGetOffsetNumber(current),
-                               maxoff = PageGetMaxOffsetNumber(page);
-       BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page);
+                               maxoff;
+       BTPageOpaque opaque;
        ItemPointerData target = so->curHeapIptr;
        BTItem          item;
        BlockNumber blkno;
 
-       LockBuffer(buf, BT_READ);
+       LockBuffer(buf, BT_READ);               /* lock buffer first! */
+       page = BufferGetPage(buf);
+       maxoff = PageGetMaxOffsetNumber(page);
+       opaque = (BTPageOpaque) PageGetSpecialPointer(page);
 
        /*
         * We use this as flag when first index tuple on page is deleted but