fix bug with quoted identifiers in ALTER SESSION SET

Author: korbash

sqlmesh/core/engine_adapter/snowflake.py

@@ -622,6 +622,12 @@ def catalog_rewriter(node: exp.Expression) -> exp.Expression:
         return expression
 
     def _to_sql(self, expression: exp.Expression, quote: bool = True, **kwargs: t.Any) -> str:
+        # Snowflake doesn't accept quoted identifiers in ALTER SESSION SET statements
+        # e.g., ALTER SESSION SET "TIMEZONE" = 'UTC' is invalid
+        # We need to disable quoting for these statements
+        if isinstance(expression, (exp.Set, exp.Alter)):
+            quote = False
+
         return super()._to_sql(
             expression=self._normalize_catalog(expression), quote=quote, **kwargs
         )

sqlmesh/core/renderer.py

@@ -419,7 +419,14 @@ def _expand(node: exp.Expression) -> exp.Expression:
 
     @contextmanager
     def _normalize_and_quote(self, query: E) -> t.Iterator[E]:
-        if self._normalize_identifiers:
+        # Snowflake doesn't accept quoted identifiers in ALTER SESSION SET statements
+        # e.g., ALTER SESSION SET "TIMEZONE" = 'UTC' is invalid
+        # SQLGlot parses "ALTER SESSION SET" as exp.Alter, not exp.Set
+        # We need to skip both normalization and quoting for these statements
+        # because quote_identifiers() modifies the AST directly and quotes persist
+        if self._dialect == "snowflake" and isinstance(query, (exp.Set, exp.Alter)):
+            yield query
+        elif self._normalize_identifiers:
             with d.normalize_and_quote(
                 query, self._dialect, self._default_catalog, quote=self._quote_identifiers
             ) as query: