Improve immutability check for JsonCtorExpr

Author: Nikita Glukhov

src/backend/optimizer/util/clauses.c

@@ -48,6 +48,8 @@
 #include "utils/builtins.h"
 #include "utils/datum.h"
 #include "utils/fmgroids.h"
+#include "utils/json.h"
+#include "utils/jsonb.h"
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/syscache.h"
@@ -665,6 +667,27 @@ contain_mutable_functions_walker(Node *node, void *context)
 								context))
 		return true;
 
+	if (IsA(node, JsonCtorExpr))
+	{
+		JsonCtorExpr *ctor = (JsonCtorExpr *) node;
+		ListCell   *lc;
+		bool		is_jsonb =
+			ctor->returning->format->format == JS_FORMAT_JSONB;
+
+		/* Check argument_type => json[b] conversions */
+		foreach(lc, ctor->args)
+		{
+			Oid			typid = exprType(lfirst(lc));
+
+			if (is_jsonb ?
+				!to_jsonb_is_immutable(typid) :
+				!to_json_is_immutable(typid))
+				return true;
+		}
+
+		/* Check all subnodes */
+	}
+
 	if (IsA(node, SQLValueFunction))
 	{
 		/* all variants of SQLValueFunction are stable */
@@ -677,12 +700,6 @@ contain_mutable_functions_walker(Node *node, void *context)
 		return true;
 	}
 
-	if (IsA(node, JsonCtorExpr))
-	{
-		/* JsonCtorExpr is stable */
-		return true;
-	}
-
 	/*
 	 * It should be safe to treat MinMaxExpr as immutable, because it will
 	 * depend on a non-cross-type btree comparison function, and those should

src/backend/utils/adt/json.c

@@ -13,6 +13,7 @@
  */
 #include "postgres.h"
 
+#include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
 #include "common/hashfn.h"
 #include "funcapi.h"
@@ -760,6 +761,38 @@ row_to_json_pretty(PG_FUNCTION_ARGS)
 	PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
 }
 
+bool
+to_json_is_immutable(Oid typoid)
+{
+	JsonTypeCategory tcategory;
+	Oid			outfuncoid;
+
+	json_categorize_type(typoid, &tcategory, &outfuncoid);
+
+	switch (tcategory)
+	{
+		case JSONTYPE_BOOL:
+		case JSONTYPE_JSON:
+			return true;
+
+		case JSONTYPE_DATE:
+		case JSONTYPE_TIMESTAMP:
+		case JSONTYPE_TIMESTAMPTZ:
+			return false;
+
+		case JSONTYPE_ARRAY:
+			return false;	/* TODO recurse into elements */
+
+		case JSONTYPE_COMPOSITE:
+			return false;	/* TODO recurse into fields */
+
+		case JSONTYPE_NUMERIC:
+		case JSONTYPE_CAST:
+		default:
+			return func_volatile(outfuncoid) == PROVOLATILE_IMMUTABLE;
+	}
+}
+
 /*
  * SQL function to_json(anyvalue)
  */

src/backend/utils/adt/jsonb.c

@@ -14,6 +14,7 @@
 
 #include "access/htup_details.h"
 #include "access/transam.h"
+#include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
 #include "funcapi.h"
 #include "libpq/pqformat.h"
@@ -1126,6 +1127,39 @@ add_jsonb(Datum val, bool is_null, JsonbInState *result,
 	datum_to_jsonb(val, is_null, result, tcategory, outfuncoid, key_scalar);
 }
 
+bool
+to_jsonb_is_immutable(Oid typoid)
+{
+	JsonbTypeCategory tcategory;
+	Oid			outfuncoid;
+
+	jsonb_categorize_type(typoid, &tcategory, &outfuncoid);
+
+	switch (tcategory)
+	{
+		case JSONBTYPE_BOOL:
+		case JSONBTYPE_JSON:
+		case JSONBTYPE_JSONB:
+			return true;
+
+		case JSONBTYPE_DATE:
+		case JSONBTYPE_TIMESTAMP:
+		case JSONBTYPE_TIMESTAMPTZ:
+			return false;
+
+		case JSONBTYPE_ARRAY:
+			return false;	/* TODO recurse into elements */
+
+		case JSONBTYPE_COMPOSITE:
+			return false;	/* TODO recurse into fields */
+
+		case JSONBTYPE_NUMERIC:
+		case JSONBTYPE_JSONCAST:
+		default:
+			return func_volatile(outfuncoid) == PROVOLATILE_IMMUTABLE;
+	}
+}
+
 /*
  * SQL function to_jsonb(anyvalue)
  */

src/include/utils/json.h

@@ -20,6 +20,7 @@
 extern void escape_json(StringInfo buf, const char *str);
 extern char *JsonEncodeDateTime(char *buf, Datum value, Oid typid,
 								const int *tzp);
+extern bool to_json_is_immutable(Oid typoid);
 extern Datum json_build_object_worker(int nargs, Datum *args, bool *nulls,
 									  Oid *types, bool absent_on_null,
 									  bool unique_keys);

src/include/utils/jsonb.h

@@ -408,7 +408,7 @@ extern char *JsonbToCStringIndent(StringInfo out, JsonbContainer *in,
 								  int estimated_len);
 extern bool JsonbExtractScalar(JsonbContainer *jbc, JsonbValue *res);
 extern const char *JsonbTypeName(JsonbValue *jb);
-
+extern bool to_jsonb_is_immutable(Oid typoid);
 extern Datum jsonb_build_object_worker(int nargs, Datum *args, bool *nulls,
 									   Oid *types, bool absent_on_null,
 									   bool unique_keys);