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, 84 insertions, 0 deletions

diff --git a/src/backend/access/gin/ginarrayproc.c b/src/backend/access/gin/ginarrayproc.c
index e02a91b82df..d04b851e3cf 100644
--- a/src/backend/access/gin/ginarrayproc.c
+++ b/src/backend/access/gin/ginarrayproc.c
@@ -218,3 +218,87 @@ ginarrayconsistent(PG_FUNCTION_ARGS)
 
 	PG_RETURN_BOOL(res);
 }
+
+/*
+ * triconsistent support function
+ */
+Datum
+ginarraytriconsistent(PG_FUNCTION_ARGS)
+{
+	GinLogicValue *check = (GinLogicValue *) PG_GETARG_POINTER(0);
+	StrategyNumber strategy = PG_GETARG_UINT16(1);
+
+	/* ArrayType  *query = PG_GETARG_ARRAYTYPE_P(2); */
+	int32		nkeys = PG_GETARG_INT32(3);
+
+	/* Pointer	   *extra_data = (Pointer *) PG_GETARG_POINTER(4); */
+	/* Datum	   *queryKeys = (Datum *) PG_GETARG_POINTER(5); */
+	bool	   *nullFlags = (bool *) PG_GETARG_POINTER(6);
+	GinLogicValue	res;
+	int32		i;
+
+	switch (strategy)
+	{
+		case GinOverlapStrategy:
+			/* must have a match for at least one non-null element */
+			res = GIN_FALSE;
+			for (i = 0; i < nkeys; i++)
+			{
+				if (!nullFlags[i])
+				{
+					if (check[i] == GIN_TRUE)
+					{
+						res = GIN_TRUE;
+						break;
+					}
+					else if (check[i] == GIN_MAYBE && res == GIN_FALSE)
+					{
+						res = GIN_MAYBE;
+					}
+				}
+			}
+			break;
+		case GinContainsStrategy:
+			/* must have all elements in check[] true, and no nulls */
+			res = GIN_TRUE;
+			for (i = 0; i < nkeys; i++)
+			{
+				if (check[i] == GIN_FALSE || nullFlags[i])
+				{
+					res = GIN_FALSE;
+					break;
+				}
+				if (check[i] == GIN_MAYBE)
+				{
+					res = GIN_MAYBE;
+				}
+			}
+			break;
+		case GinContainedStrategy:
+			/* can't do anything else useful here */
+			res = GIN_MAYBE;
+			break;
+		case GinEqualStrategy:
+			/*
+			 * Must have all elements in check[] true; no discrimination
+			 * against nulls here.	This is because array_contain_compare and
+			 * array_eq handle nulls differently ...
+			 */
+			res = GIN_MAYBE;
+			for (i = 0; i < nkeys; i++)
+			{
+				if (check[i] == GIN_FALSE)
+				{
+					res = GIN_FALSE;
+					break;
+				}
+			}
+			break;
+		default:
+			elog(ERROR, "ginarrayconsistent: unknown strategy number: %d",
+				 strategy);
+			res = false;
+	}
+
+	PG_RETURN_GIN_LOGIC_VALUE(res);
+}