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 272a9ca7c09db884e6fd2a7ff38d9d578bfb8e03..0ea4f3fe284b4b544309a7c983d1097ce29449bb 100644 (file)
--- a/src/backend/access/gin/gindatapage.c
+++ b/src/backend/access/gin/gindatapage.c
@@ -642,20 +642,24 @@ 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);
            }
        }