allow-query-cancel-in-spgdoinsert-WIP.patch

diff --git a/src/backend/access/spgist/spgdoinsert.c b/src/backend/access/spgist/spgdoinsert.c
index 4d380c99f0..82e68c4ab7 100644
--- a/src/backend/access/spgist/spgdoinsert.c
+++ b/src/backend/access/spgist/spgdoinsert.c
@@ -1905,13 +1905,14 @@ spgSplitNodeAction(Relation index, SpGistState *state,
  * Insert one item into the index.
  *
  * Returns true on success, false if we failed to complete the insertion
- * because of conflict with a concurrent insert.  In the latter case,
- * caller should re-call spgdoinsert() with the same args.
+ * (typically because of conflict with a concurrent insert).  In the latter
+ * case, caller should re-call spgdoinsert() with the same args.
  */
 bool
 spgdoinsert(Relation index, SpGistState *state,
 			ItemPointer heapPtr, Datum *datums, bool *isnulls)
 {
+	bool		result = true;
 	TupleDesc	leafDescriptor = state->leafTupDesc;
 	bool		isnull = isnulls[spgKeyColumn];
 	int			level = 0;
@@ -2019,9 +2020,17 @@ spgdoinsert(Relation index, SpGistState *state,
 		/*
 		 * Bail out if query cancel is pending.  We must have this somewhere
 		 * in the loop since a broken opclass could produce an infinite
-		 * picksplit loop.
+		 * picksplit loop.  Moreover, because it's typically the case that
+		 * we're holding buffer lock(s), ProcessInterrupts() won't be able to
+		 * throw an error now.  Hence, if we see that InterruptPending remains
+		 * true, break out of the loop and deal with the problem below.
 		 */
 		CHECK_FOR_INTERRUPTS();
+		if (unlikely(InterruptPending))
+		{
+			result = false;
+			break;
+		}
 
 		if (current.blkno == InvalidBlockNumber)
 		{
@@ -2140,10 +2149,15 @@ spgdoinsert(Relation index, SpGistState *state,
 			 * spgAddNode and spgSplitTuple cases will loop back to here to
 			 * complete the insertion operation.  Just in case the choose
 			 * function is broken and produces add or split requests
-			 * repeatedly, check for query cancel.
+			 * repeatedly, check for query cancel (see comments above).
 			 */
 	process_inner_tuple:
 			CHECK_FOR_INTERRUPTS();
+			if (unlikely(InterruptPending))
+			{
+				result = false;
+				break;
+			}
 
 			innerTuple = (SpGistInnerTuple) PageGetItem(current.page,
 														PageGetItemId(current.page, current.offnum));
@@ -2267,5 +2281,12 @@ spgdoinsert(Relation index, SpGistState *state,
 		UnlockReleaseBuffer(parent.buffer);
 	}
 
-	return true;
+	/*
+	 * Finally, check for interrupts again.  If there was one,
+	 * ProcessInterrupts() will be able to throw the error now.  But should it
+	 * not do so for some reason, return false to cause a retry.
+	 */
+	CHECK_FOR_INTERRUPTS();
+
+	return result;
 }