Fix: fix perf issues with nested left joins

tobymao · Oct 1, 2023 · 5fb7174 · 5fb7174
1 parent a794bfe
commit 5fb7174
Show file tree

Hide file tree

Showing 2 changed files with 30 additions and 5 deletions.
diff --git a/sqlglot/parser.py b/sqlglot/parser.py
@@ -2461,17 +2461,17 @@ def _parse_join(
             kwargs["using"] = self._parse_wrapped_id_vars()
         elif not (kind and kind.token_type == TokenType.CROSS):
             index = self._index
-            joins = self._parse_joins()
+            join = self._parse_join()
 
-            if joins and self._match(TokenType.ON):
+            if join and self._match(TokenType.ON):
                 kwargs["on"] = self._parse_conjunction()
-            elif joins and self._match(TokenType.USING):
+            elif join and self._match(TokenType.USING):
                 kwargs["using"] = self._parse_wrapped_id_vars()
             else:
-                joins = None
+                join = None
                 self._retreat(index)
 
-            kwargs["this"].set("joins", joins)
+            kwargs["this"].set("joins", [join] if join else None)
 
         comments = [c for token in (method, side, kind) if token for c in token.comments]
         return self.expression(exp.Join, comments=comments, **kwargs)

diff --git a/tests/test_parser.py b/tests/test_parser.py
@@ -690,6 +690,31 @@ def test_parse_nested(self):
             LEFT JOIN b ON a.id = b.id
             """
         )
+
+        self.assertIsNotNone(query)
+
+        query = parse_one(
+            """
+            SELECT *
+            FROM a
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            LEFT JOIN UNNEST(ARRAY[])
+            """
+        )
+
         self.assertIsNotNone(query)
         self.assertLessEqual(time.time() - now, 0.2)