fix(flink): #415 fix supporting json function's different type (#416)

Co-authored-by: zhaoge <>

Author: Cythia828

src/grammar/flink/FlinkSqlLexer.g4

@@ -211,6 +211,7 @@ KW_INTERVAL            : 'INTERVAL';
 KW_INTO                : 'INTO';
 KW_IS                  : 'IS';
 KW_JOIN                : 'JOIN';
+KW_JSON                : 'JSON';
 KW_JSON_ARRAY          : 'JSON_ARRAY';
 KW_JSON_ARRAYAGG       : 'JSON_ARRAYAGG';
 KW_JSON_EXECUTION_PLAN : 'JSON_EXECUTION_PLAN';

src/grammar/flink/FlinkSqlParser.g4

@@ -726,6 +726,7 @@ predicate
     | KW_IS KW_NOT? kind=(KW_TRUE | KW_FALSE | KW_UNKNOWN | KW_NULL)
     | KW_IS KW_NOT? kind=KW_DISTINCT KW_FROM right=valueExpression
     | KW_NOT? kind=KW_SIMILAR KW_TO right=valueExpression (KW_ESCAPE stringLiteral)?
+    | KW_IS KW_JSON (KW_VALUE | KW_ARRAY | identifier)?
     ;
 
 likePredicate
@@ -1179,6 +1180,13 @@ reservedKeywordsUsedAsFuncName
     | KW_VAR_SAMP
     | KW_WEEK
     | KW_YEAR
+    | KW_JSON_VALUE
+    | KW_JSON_EXISTS
+    | KW_JSON_QUERY
+    | KW_JSON_OBJECT
+    | KW_JSON_OBJECTAGG
+    | KW_JSON_ARRAY
+    | KW_JSON_ARRAYAGG
     ;
 
 nonReservedKeywords