jsonpath: add support for .type() method

This commit adds support for the `.type()` method in JSONPath queries,
which returns a string descripbing the type of the current JSON value
("object", "array", "string", "number", "boolean", "null").

Release note (sql change): Add support for `.type()` method for JSONPath
queries. For example, `SELECT jsonb_path_query('[1, 2, 3]', '$.type()');`.

Author: normanchenn

pkg/sql/logictest/testdata/logic_test/jsonb_path_query

@@ -1469,3 +1469,85 @@ SELECT jsonb_path_query('[12, {"a": 13}, {"b": 14}, "ccc", true]', '$[2 - 1 to $
 {"a": 13}
 {"b": 14}
 "ccc"
+
+query T
+SELECT jsonb_path_query('{}', '$.type()');
+----
+"object"
+
+query T
+SELECT jsonb_path_query('[]', '$.type()');
+----
+"array"
+
+query T
+SELECT jsonb_path_query('"hello"', '$.type()');
+----
+"string"
+
+query T
+SELECT jsonb_path_query('0', '$.type()');
+----
+"number"
+
+query T
+SELECT jsonb_path_query('0.1', '$.type()');
+----
+"number"
+
+query T
+SELECT jsonb_path_query('true', '$.type()');
+----
+"boolean"
+
+query T
+SELECT jsonb_path_query('false', '$.type()');
+----
+"boolean"
+
+query T
+SELECT jsonb_path_query('null', '$.type()');
+----
+"null"
+
+query T
+SELECT jsonb_path_query('null', '"123".type()');
+----
+"string"
+
+# TODO(#144258): should be "number", but the scanner doesn't scan this properly.
+statement error pgcode 42601 pq: at or near \"trailing junk after numeric literal
+SELECT jsonb_path_query('null', '(123).type()');
+
+query T
+SELECT jsonb_path_query('null', 'true.type()');
+----
+"boolean"
+
+query T
+SELECT jsonb_path_query('null', 'null.type()');
+----
+"null"
+
+query T rowsort
+SELECT jsonb_path_query('[null,1,true,"a",[],{}]', '$[*].type()');
+----
+"null"
+"number"
+"boolean"
+"string"
+"array"
+"object"
+
+query T
+SELECT jsonb_path_query('[null,1,true,"a",[],{}]', 'lax $.type()');
+----
+"array"
+
+statement error pgcode 22033 pq: jsonpath array subscript is not a single numeric value
+SELECT jsonb_path_query('[1,2,3]', '$[last ? (@.type() == "string")]');
+
+query T
+SELECT jsonb_path_query('[1,2,3]', '$[last ? (@.type() == "number")]');
+----
+3

pkg/sql/logictest/testdata/logic_test/jsonpath

@@ -162,9 +162,6 @@ SELECT '@'::JSONPATH
 statement error unimplemented
 SELECT '$ ? (@ like_regex ".*" flag "i")'::JSONPATH;
 
-statement error unimplemented
-SELECT '$.type()'::JSONPATH;
-
 statement error unimplemented
 SELECT '$.keyvalue()'::JSONPATH;
 

pkg/util/jsonpath/eval/method.go

@@ -26,6 +26,9 @@ func (ctx *jsonpathCtx) evalMethod(
 			return nil, err
 		}
 		return []json.JSON{json.FromInt(size)}, nil
+	case jsonpath.TypeMethod:
+		t := ctx.evalType(jsonValue)
+		return []json.JSON{json.FromString(t)}, nil
 	default:
 		return nil, errUnimplemented
 	}
@@ -40,3 +43,12 @@ func (ctx *jsonpathCtx) evalSize(jsonValue json.JSON) (int, error) {
 	}
 	return jsonValue.Len(), nil
 }
+
+func (ctx *jsonpathCtx) evalType(jsonValue json.JSON) string {
+	// When jsonValue is a number, json.Type.String() returns "numeric", but
+	// postgres returns "number".
+	if jsonValue.Type() == json.NumberJSONType {
+		return "number"
+	}
+	return jsonValue.Type().String()
+}

pkg/util/jsonpath/method.go

@@ -12,10 +12,12 @@ type MethodType int
 const (
 	InvalidMethod MethodType = iota
 	SizeMethod
+	TypeMethod
 )
 
 var MethodTypeStrings = map[MethodType]string{
 	SizeMethod: "size",
+	TypeMethod: "type",
 }
 
 type Method struct {

pkg/util/jsonpath/parser/jsonpath.y

@@ -529,7 +529,7 @@ method:
   }
 | TYPE
   {
-    return unimplemented(jsonpathlex, ".type()")
+    $$.val = jsonpath.Method{Type: jsonpath.TypeMethod}
   }
 | KEYVALUE
   {

pkg/util/jsonpath/parser/testdata/jsonpath

@@ -594,6 +594,11 @@ parse
 ----
 $."a".size() -- normalized!
 
+parse
+$.a.type()
+----
+$."a".type() -- normalized!
+
 # postgres allows floats as array indexes
 # parse
 # $.abc[1.0]