Fix bug in compressed GIN data leaf page splitting code.

The list of posting lists it's dealing with can contain placeholders for
deleted posting lists. The placeholders are kept around so that they can
be WAL-logged, but we must be careful to not try to access them.

This fixes bug #11280, reported by Mårten Svantesson. Backpatch to 9.4,
where the compressed data leaf page code was added.

diff --git a/src/backend/access/gin/gindatapage.c b/src/backend/access/gin/gindatapage.c
index 5b7c49654c65d95626b2edd84d8b673810165bd5..76e0cb3e19f7bdea54edb9e468efea1d902b8940 100644 (file)
--- a/src/backend/access/gin/gindatapage.c
+++ b/src/backend/access/gin/gindatapage.c
@@ -641,20 +641,24 @@ dataPlaceToPageLeaf(GinBtree btree, Buffer buf, GinBtreeStack *stack,
            {
                lastleftinfo = dlist_container(leafSegmentInfo, node, leaf->lastleft);
 
-               segsize = SizeOfGinPostingList(lastleftinfo->seg);
-               if (append)
+               /* ignore deleted segments */
+               if (lastleftinfo->action != GIN_SEGMENT_DELETE)
                {
-                   if ((leaf->lsize - segsize) - (leaf->lsize - segsize) < BLCKSZ / 4)
-                       break;
+                   segsize = SizeOfGinPostingList(lastleftinfo->seg);
+                   if (append)
+                   {
+                       if ((leaf->lsize - segsize) - (leaf->lsize - segsize) < BLCKSZ / 4)
+                           break;
+                   }
+                   else
+                   {
+                       if ((leaf->lsize - segsize) - (leaf->rsize + segsize) < 0)
+                           break;
+                   }
+
+                   leaf->lsize -= segsize;
+                   leaf->rsize += segsize;
                }
-               else
-               {
-                   if ((leaf->lsize - segsize) - (leaf->rsize + segsize) < 0)
-                       break;
-               }
-
-               leaf->lsize -= segsize;
-               leaf->rsize += segsize;
                leaf->lastleft = dlist_prev_node(&leaf->segments, leaf->lastleft);
            }
        }