Allow opclasses to provide tri-valued GIN consistent functions.

With the GIN "fast scan" feature, GIN can skip items without fetching all
the keys for them, if it can prove that they don't match regardless of
those keys. So far, it has done the proving by calling the boolean
consistent function with all combinations of TRUE/FALSE for the unfetched
keys, but since that's O(n^2), it becomes unfeasible with more than a few
keys. We can avoid calling consistent with all the combinations, if we can
tell the operator class implementation directly which keys are unknown.

This commit includes a triConsistent function for the built-in array and
tsvector opclasses.

Alexander Korotkov, with some changes by me.

1 files changed, 25 insertions, 3 deletions

diff --git a/src/backend/access/gin/ginutil.c b/src/backend/access/gin/ginutil.c
index 486f2ef1f11..4dadb50dcaa 100644
--- a/src/backend/access/gin/ginutil.c
+++ b/src/backend/access/gin/ginutil.c
@@ -67,9 +67,31 @@ initGinState(GinState *state, Relation index)
 		fmgr_info_copy(&(state->extractQueryFn[i]),
 					   index_getprocinfo(index, i + 1, GIN_EXTRACTQUERY_PROC),
 					   CurrentMemoryContext);
-		fmgr_info_copy(&(state->consistentFn[i]),
-					   index_getprocinfo(index, i + 1, GIN_CONSISTENT_PROC),
-					   CurrentMemoryContext);
+		/*
+		 * Check opclass capability to do tri-state or binary logic consistent
+		 * check.
+		 */
+		if (index_getprocid(index, i + 1, GIN_TRICONSISTENT_PROC) != InvalidOid)
+		{
+			fmgr_info_copy(&(state->triConsistentFn[i]),
+			   index_getprocinfo(index, i + 1, GIN_TRICONSISTENT_PROC),
+						   CurrentMemoryContext);
+		}
+
+		if (index_getprocid(index, i + 1, GIN_CONSISTENT_PROC) != InvalidOid)
+		{
+			fmgr_info_copy(&(state->consistentFn[i]),
+						   index_getprocinfo(index, i + 1, GIN_CONSISTENT_PROC),
+						   CurrentMemoryContext);
+		}
+
+		if (state->consistentFn[i].fn_oid == InvalidOid &&
+			state->triConsistentFn[i].fn_oid == InvalidOid)
+		{
+			elog(ERROR, "missing GIN support function (%d or %d) for attribute %d of index \"%s\"",
+				 GIN_CONSISTENT_PROC, GIN_TRICONSISTENT_PROC,
+				 i + 1, RelationGetRelationName(index));
+		}
 
 		/*
 		 * Check opclass capability to do partial match.