Fix GiST buffering build bug, which caused "failed to re-find parent" errors.

We use a hash table to track the parents of inner pages, but when inserting
to a leaf page, the caller of gistbufferinginserttuples() must pass a
correct block number of the leaf's parent page. Before gistProcessItup()
descends to a child page, it checks if the downlink needs to be adjusted to
accommodate the new tuple, and updates the downlink if necessary. However,
updating the downlink might require splitting the page, which might move the
downlink to a page to the right. gistProcessItup() doesn't realize that, so
when it descends to the leaf page, it might pass an out-of-date parent block
number as a result. Fix that by returning the block a tuple was inserted to
from gistbufferinginserttuples().

This fixes the bug reported by Zdeněk Jílovec.

1 files changed, 26 insertions, 7 deletions

diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 64ad2d749b0..9c6625bba3a 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -148,16 +148,22 @@ gistinsert(PG_FUNCTION_ARGS)
  * pages are released; note that new tuple(s) are *not* on the root page
  * but in one of the new child pages.
  *
+ * If 'newblkno' is not NULL, returns the block number of page the first
+ * new/updated tuple was inserted to. Usually it's the given page, but could
+ * be its right sibling if the page was split.
+ *
  * Returns 'true' if the page was split, 'false' otherwise.
  */
 bool
 gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 				Buffer buffer,
 				IndexTuple *itup, int ntup, OffsetNumber oldoffnum,
+				BlockNumber *newblkno,
 				Buffer leftchildbuf,
 				List **splitinfo,
 				bool markfollowright)
 {
+	BlockNumber blkno = BufferGetBlockNumber(buffer);
 	Page		page = BufferGetPage(buffer);
 	bool		is_leaf = (GistPageIsLeaf(page)) ? true : false;
 	XLogRecPtr	recptr;
@@ -199,7 +205,6 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 		BlockNumber oldrlink = InvalidBlockNumber;
 		GistNSN		oldnsn = 0;
 		SplitedPageLayout rootpg;
-		BlockNumber blkno = BufferGetBlockNumber(buffer);
 		bool		is_rootsplit;
 
 		is_rootsplit = (blkno == GIST_ROOT_BLKNO);
@@ -319,9 +324,19 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 
 			for (i = 0; i < ptr->block.num; i++)
 			{
-				if (PageAddItem(ptr->page, (Item) data, IndexTupleSize((IndexTuple) data), i + FirstOffsetNumber, false, false) == InvalidOffsetNumber)
+				IndexTuple	thistup = (IndexTuple) data;
+
+				if (PageAddItem(ptr->page, (Item) data, IndexTupleSize(thistup), i + FirstOffsetNumber, false, false) == InvalidOffsetNumber)
 					elog(ERROR, "failed to add item to index page in \"%s\"", RelationGetRelationName(rel));
-				data += IndexTupleSize((IndexTuple) data);
+
+				/*
+				 * If this is the first inserted/updated tuple, let the caller
+				 * know which page it landed on.
+				 */
+				if (newblkno && ItemPointerEquals(&thistup->t_tid, &(*itup)->t_tid))
+					*newblkno = ptr->block.blkno;
+
+				data += IndexTupleSize(thistup);
 			}
 
 			/* Set up rightlinks */
@@ -436,6 +451,9 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 			recptr = GetXLogRecPtrForTemp();
 			PageSetLSN(page, recptr);
 		}
+
+		if (newblkno)
+			*newblkno = blkno;
 	}
 
 	/*
@@ -1074,9 +1092,9 @@ gistinserttuple(GISTInsertState *state, GISTInsertStack *stack,
  *	  is kept pinned.
  *	- Lock and pin on 'rightchild' are always released.
  *
- * Returns 'true' if the page had to be split. Note that if the page had
- * be split, the inserted/updated might've been inserted to a right sibling
- * of stack->buffer instead of stack->buffer itself.
+ * Returns 'true' if the page had to be split. Note that if the page was
+ * split, the inserted/updated tuples might've been inserted to a right
+ * sibling of stack->buffer instead of stack->buffer itself.
  */
 static bool
 gistinserttuples(GISTInsertState *state, GISTInsertStack *stack,
@@ -1091,7 +1109,8 @@ gistinserttuples(GISTInsertState *state, GISTInsertStack *stack,
 	/* Insert the tuple(s) to the page, splitting the page if necessary */
 	is_split = gistplacetopage(state->r, state->freespace, giststate,
 							   stack->buffer,
-							   tuples, ntup, oldoffnum,
+							   tuples, ntup,
+							   oldoffnum, NULL,
 							   leftchild,
 							   &splitinfo,
 							   true);