Fix: postgres exponent precedence closes tobymao#1555

sqlglot/__init__.py

@@ -181,7 +181,7 @@ def transpile(
     Returns:
         The list of transpiled SQL statements.
     """
-    write = write or read if identity else write
+    write = (read if write is None else write) if identity else write
     return [
         Dialect.get_or_raise(write)().generate(expression, **opts)
         for expression in parse(sql, read, error_level=error_level)

sqlglot/dialects/postgres.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import typing as t
+
 from sqlglot import exp, generator, parser, tokens, transforms
 from sqlglot.dialects.dialect import (
     Dialect,
@@ -273,8 +275,7 @@ class Parser(parser.Parser):
             TokenType.HASH: exp.BitwiseXor,
         }
 
-        FACTOR = {
-            **parser.Parser.FACTOR,
+        EXPONENT = {
             TokenType.CARET: exp.Pow,
         }
 
@@ -285,6 +286,12 @@ class Parser(parser.Parser):
             TokenType.LT_AT: binary_range_parser(exp.ArrayContained),
         }
 
+        def _parse_factor(self) -> t.Optional[exp.Expression]:
+            return self._parse_tokens(self._parse_exponent, self.FACTOR)
+
+        def _parse_exponent(self) -> t.Optional[exp.Expression]:
+            return self._parse_tokens(self._parse_unary, self.EXPONENT)
+
         def _parse_date_part(self) -> exp.Expression:
             part = self._parse_type()
             self._match(TokenType.COMMA)

tests/dialects/test_postgres.py

@@ -491,6 +491,14 @@ def test_postgres(self):
             },
         )
 
+        self.validate_all(
+            "x / y ^ z",
+            write={
+                "": "x / POWER(y, z)",
+                "postgres": "x / y ^ z",
+            },
+        )
+
         self.assertIsInstance(parse_one("id::UUID", read="postgres"), exp.TryCast)
 
     def test_bool_or(self):