SQL/JSON query functions

This introduces the SQL/JSON functions for querying JSON data using
jsonpath expressions. The functions are:

JSON_EXISTS()
JSON_QUERY()
JSON_VALUE()

All of these functions only operate on jsonb. The workaround for now is
to cast the argument to jsonb.

JSON_EXISTS() tests if the jsonpath expression applied to the jsonb
value yields any values. JSON_VALUE() must return a single value, and an
error occurs if it tries to return multiple values. JSON_QUERY() must
return a json object or array, and there are various WRAPPER options for
handling scalar or multi-value results. Both these functions have
options for handling EMPTY and ERROR conditions.

Nikita Glukhov

Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby.

Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru

1 files changed, 127 insertions, 0 deletions

diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 084d98b34cc..f6dd61370c0 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -977,6 +977,42 @@ _equalJsonArrayQueryConstructor(const JsonArrayQueryConstructor *a,
 }
 
 static bool
+_equalJsonFuncExpr(const JsonFuncExpr *a, const JsonFuncExpr *b)
+{
+	COMPARE_SCALAR_FIELD(op);
+	COMPARE_NODE_FIELD(common);
+	COMPARE_NODE_FIELD(output);
+	COMPARE_NODE_FIELD(on_empty);
+	COMPARE_NODE_FIELD(on_error);
+	COMPARE_SCALAR_FIELD(wrapper);
+	COMPARE_SCALAR_FIELD(omit_quotes);
+	COMPARE_LOCATION_FIELD(location);
+
+	return true;
+}
+
+static bool
+_equalJsonCommon(const JsonCommon *a, const JsonCommon *b)
+{
+	COMPARE_NODE_FIELD(expr);
+	COMPARE_NODE_FIELD(pathspec);
+	COMPARE_STRING_FIELD(pathname);
+	COMPARE_NODE_FIELD(passing);
+	COMPARE_LOCATION_FIELD(location);
+
+	return true;
+}
+
+static bool
+_equalJsonArgument(const JsonArgument *a, const JsonArgument *b)
+{
+	COMPARE_NODE_FIELD(val);
+	COMPARE_STRING_FIELD(name);
+
+	return true;
+}
+
+static bool
 _equalJsonIsPredicate(const JsonIsPredicate *a,
 					  const JsonIsPredicate *b)
 {
@@ -989,6 +1025,76 @@ _equalJsonIsPredicate(const JsonIsPredicate *a,
 }
 
 /*
+ * _equalJsonBehavior
+ */
+static bool
+_equalJsonBehavior(const JsonBehavior *a, const JsonBehavior *b)
+{
+	COMPARE_SCALAR_FIELD(btype);
+	COMPARE_NODE_FIELD(default_expr);
+
+	return true;
+}
+
+/*
+ * _equalJsonExpr
+ */
+static bool
+_equalJsonExpr(const JsonExpr *a, const JsonExpr *b)
+{
+	COMPARE_SCALAR_FIELD(op);
+	COMPARE_NODE_FIELD(formatted_expr);
+	COMPARE_NODE_FIELD(result_coercion);
+	COMPARE_NODE_FIELD(format);
+	COMPARE_NODE_FIELD(path_spec);
+	COMPARE_NODE_FIELD(passing_values);
+	COMPARE_NODE_FIELD(passing_names);
+	COMPARE_NODE_FIELD(returning);
+	COMPARE_NODE_FIELD(on_error);
+	COMPARE_NODE_FIELD(on_empty);
+	COMPARE_NODE_FIELD(coercions);
+	COMPARE_SCALAR_FIELD(wrapper);
+	COMPARE_SCALAR_FIELD(omit_quotes);
+	COMPARE_LOCATION_FIELD(location);
+
+	return true;
+}
+
+/*
+ * _equalJsonCoercion
+ */
+static bool
+_equalJsonCoercion(const JsonCoercion *a, const JsonCoercion *b)
+{
+	COMPARE_NODE_FIELD(expr);
+	COMPARE_SCALAR_FIELD(via_populate);
+	COMPARE_SCALAR_FIELD(via_io);
+	COMPARE_SCALAR_FIELD(collation);
+
+	return true;
+}
+
+/*
+ * _equalJsonItemCoercions
+ */
+static bool
+_equalJsonItemCoercions(const JsonItemCoercions *a, const JsonItemCoercions *b)
+{
+	COMPARE_NODE_FIELD(null);
+	COMPARE_NODE_FIELD(string);
+	COMPARE_NODE_FIELD(numeric);
+	COMPARE_NODE_FIELD(boolean);
+	COMPARE_NODE_FIELD(date);
+	COMPARE_NODE_FIELD(time);
+	COMPARE_NODE_FIELD(timetz);
+	COMPARE_NODE_FIELD(timestamp);
+	COMPARE_NODE_FIELD(timestamptz);
+	COMPARE_NODE_FIELD(composite);
+
+	return true;
+}
+
+/*
  * Stuff from pathnodes.h
  */
 
@@ -3561,6 +3667,18 @@ equal(const void *a, const void *b)
 		case T_JsonIsPredicate:
 			retval = _equalJsonIsPredicate(a, b);
 			break;
+		case T_JsonBehavior:
+			retval = _equalJsonBehavior(a, b);
+			break;
+		case T_JsonExpr:
+			retval = _equalJsonExpr(a, b);
+			break;
+		case T_JsonCoercion:
+			retval = _equalJsonCoercion(a, b);
+			break;
+		case T_JsonItemCoercions:
+			retval = _equalJsonItemCoercions(a, b);
+			break;
 
 			/*
 			 * RELATION NODES
@@ -4174,6 +4292,15 @@ equal(const void *a, const void *b)
 		case T_JsonArrayAgg:
 			retval = _equalJsonArrayAgg(a, b);
 			break;
+		case T_JsonFuncExpr:
+			retval = _equalJsonFuncExpr(a, b);
+			break;
+		case T_JsonCommon:
+			retval = _equalJsonCommon(a, b);
+			break;
+		case T_JsonArgument:
+			retval = _equalJsonArgument(a, b);
+			break;
 
 		default:
 			elog(ERROR, "unrecognized node type: %d",