accept JSON_TABLE both as an unquoted table name and a table-valued function

see apache#1123 (comment)

Author: lovasoa

src/parser/mod.rs

@@ -7515,7 +7515,11 @@ impl<'a> Parser<'a> {
                 with_offset,
                 with_offset_alias,
             })
-        } else if self.parse_keyword(Keyword::JSON_TABLE) {
+        } else if matches!(
+            self.peek_token().token, Token::Word(w)
+            if w.keyword == Keyword::JSON_TABLE && self.peek_nth_token(1).token == Token::LParen
+        ) {
+            self.expect_keyword(Keyword::JSON_TABLE)?;
             self.expect_token(&Token::LParen)?;
             let json_expr = self.parse_expr()?;
             self.expect_token(&Token::Comma)?;

tests/sqlparser_postgres.rs

@@ -2328,6 +2328,26 @@ fn test_json() {
     );
 }
 
+#[test]
+fn parse_json_table_is_not_reserved() {
+    // JSON_TABLE is not a reserved keyword in PostgreSQL, even though it is in SQL:2023
+    // see: https://en.wikipedia.org/wiki/List_of_SQL_reserved_words
+    match pg().verified_only_select("SELECT * FROM JSON_TABLE") {
+        Select { from, .. } => {
+            assert_eq!(1, from.len());
+            match &from[0].relation {
+                TableFactor::Table {
+                    name: ObjectName(name),
+                    ..
+                } => {
+                    assert_eq!("JSON_TABLE", name[0].value);
+                }
+                _ => unreachable!(),
+            }
+        }
+    }
+}
+
 #[test]
 fn test_composite_value() {
     let sql = "SELECT (on_hand.item).name FROM on_hand WHERE (on_hand.item).price > 9";