fix(mysql): support SHOW TABLES IN <schema> parsing (#7537)

MariaDB and MySQL both accept `SHOW TABLES IN schema` as a synonym
for `SHOW TABLES FROM schema`, but the parser only handled `FROM`.
The `IN` token was being consumed as a potential log-file specifier
(for BINLOG/RELAYLOG EVENTS) and then lost, leaving the schema
identifier unconsumed and raising a ParseError.

Save the parser index before consuming `IN`; if no string literal
follows, retreat so the schema-name branch can match `IN` as an
alias for `FROM`. BINLOG/RELAYLOG EVENTS behavior is preserved by
the existing test_show_events coverage.

Author: mkcorneli

sqlglot/parsers/mysql.py

@@ -408,7 +408,13 @@ def _parse_show_mysql(
         else:
             target_id = None
 
-        log = self._parse_string() if self._match_text_seq("IN") else None
+        index = self._index
+        if self._match_text_seq("IN"):
+            log = self._parse_string()
+            if log is None:
+                self._retreat(index)
+        else:
+            log = None
 
         if this in ("BINLOG EVENTS", "RELAYLOG EVENTS"):
             position = self._parse_number() if self._match_text_seq("FROM") else None
@@ -417,7 +423,7 @@ def _parse_show_mysql(
             position = None
             db = None
 
-            if self._match(TokenType.FROM):
+            if self._match(TokenType.FROM) or self._match_text_seq("IN"):
                 db = self._parse_id_var()
             elif self._match(TokenType.DOT):
                 db = target_id

tests/dialects/test_mysql.py

@@ -1411,6 +1411,14 @@ def test_show_tables(self):
         self.assertIsInstance(show.args["like"], exp.Literal)
         self.assertEqual(show.text("like"), "%foo%")
 
+        show = self.validate_identity("SHOW TABLES IN test", "SHOW TABLES FROM test")
+        self.assertEqual(show.name, "TABLES")
+        self.assertEqual(show.text("db"), "test")
+
+        show = self.validate_identity("SHOW FULL TABLES IN test", "SHOW FULL TABLES FROM test")
+        self.assertTrue(show.args["full"])
+        self.assertEqual(show.text("db"), "test")
+
     def test_set_variable(self):
         cmd = self.parse_one("SET SESSION x = 1")
         item = cmd.expressions[0]