1 files changed, 26 insertions, 18 deletions

diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index 1d6b752a28b..2a9aeec8061 100644
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -15,7 +15,6 @@
 
 #include "access/htup_details.h"
 #include "access/transam.h"
-#include "catalog/pg_cast.h"
 #include "catalog/pg_type.h"
 #include "executor/spi.h"
 #include "lib/stringinfo.h"
@@ -1281,10 +1280,14 @@ json_categorize_type(Oid typoid,
 	/* Look through any domain */
 	typoid = getBaseType(typoid);
 
-	/* We'll usually need to return the type output function */
-	getTypeOutputInfo(typoid, outfuncoid, &typisvarlena);
+	*outfuncoid = InvalidOid;
+
+	/*
+	 * We need to get the output function for everything except date and
+	 * timestamp types, array and composite types, booleans,
+	 * and non-builtin types  where there's a cast to json.
+	 */
 
-	/* Check for known types */
 	switch (typoid)
 	{
 		case BOOLOID:
@@ -1297,6 +1300,7 @@ json_categorize_type(Oid typoid,
 		case FLOAT4OID:
 		case FLOAT8OID:
 		case NUMERICOID:
+			getTypeOutputInfo(typoid, outfuncoid, &typisvarlena);
 			*tcategory = JSONTYPE_NUMERIC;
 			break;
 
@@ -1314,6 +1318,7 @@ json_categorize_type(Oid typoid,
 
 		case JSONOID:
 		case JSONBOID:
+			getTypeOutputInfo(typoid, outfuncoid, &typisvarlena);
 			*tcategory = JSONTYPE_JSON;
 			break;
 
@@ -1330,23 +1335,26 @@ json_categorize_type(Oid typoid,
 				/* but let's look for a cast to json, if it's not built-in */
 				if (typoid >= FirstNormalObjectId)
 				{
-					HeapTuple	tuple;
+					Oid castfunc;
+					CoercionPathType ctype;
 
-					tuple = SearchSysCache2(CASTSOURCETARGET,
-											ObjectIdGetDatum(typoid),
-											ObjectIdGetDatum(JSONOID));
-					if (HeapTupleIsValid(tuple))
+					ctype = find_coercion_pathway(JSONOID, typoid,
+												  COERCION_EXPLICIT, &castfunc);
+					if (ctype == COERCION_PATH_FUNC && OidIsValid(castfunc))
 					{
-						Form_pg_cast castForm = (Form_pg_cast) GETSTRUCT(tuple);
-
-						if (castForm->castmethod == COERCION_METHOD_FUNCTION)
-						{
-							*tcategory = JSONTYPE_CAST;
-							*outfuncoid = castForm->castfunc;
-						}
-
-						ReleaseSysCache(tuple);
+						*tcategory = JSONTYPE_CAST;
+						*outfuncoid = castfunc;
 					}
+					else
+					{
+						/* non builtin type with no cast */
+						getTypeOutputInfo(typoid, outfuncoid, &typisvarlena);
+					}
+				}
+				else
+				{
+					/* any other builtin type */
+					getTypeOutputInfo(typoid, outfuncoid, &typisvarlena);
 				}
 			}
 			break;