Fix(snowflake): convert VALUES with invalid expressions into UNION ALL

sqlglot/dialects/snowflake.py

@@ -852,6 +852,16 @@ class Generator(generator.Generator):
             exp.VolatileProperty: exp.Properties.Location.UNSUPPORTED,
         }
 
+        UNSUPPORTED_VALUES_EXPRESSIONS = {
+            exp.Struct,
+        }
+
+        def values_sql(self, expression: exp.Values, values_as_table: bool = True) -> str:
+            if expression.find(*self.UNSUPPORTED_VALUES_EXPRESSIONS):
+                values_as_table = False
+
+            return super().values_sql(expression, values_as_table=values_as_table)
+
         def datatype_sql(self, expression: exp.DataType) -> str:
             expressions = expression.expressions
             if (

sqlglot/generator.py

@@ -1746,9 +1746,11 @@ def update_sql(self, expression: exp.Update) -> str:
         sql = f"UPDATE {this} SET {set_sql}{expression_sql}{order}{limit}"
         return self.prepend_ctes(expression, sql)
 
-    def values_sql(self, expression: exp.Values) -> str:
+    def values_sql(self, expression: exp.Values, values_as_table: bool = True) -> str:
+        values_as_table = values_as_table and self.VALUES_AS_TABLE
+
         # The VALUES clause is still valid in an `INSERT INTO ..` statement, for example
-        if self.VALUES_AS_TABLE or not expression.find_ancestor(exp.From, exp.Join):
+        if values_as_table or not expression.find_ancestor(exp.From, exp.Join):
             args = self.expressions(expression)
             alias = self.sql(expression, "alias")
             values = f"VALUES{self.seg('')}{args}"

tests/dialects/test_snowflake.py

@@ -1416,14 +1416,25 @@ def test_values(self):
                 "spark": "SELECT `c0`, `c1` FROM (VALUES (1, 2), (3, 4)) AS `t0`(`c0`, `c1`)",
             },
         )
-
         self.validate_all(
             """SELECT $1 AS "_1" FROM VALUES ('a'), ('b')""",
             write={
                 "snowflake": """SELECT $1 AS "_1" FROM (VALUES ('a'), ('b'))""",
                 "spark": """SELECT ${1} AS `_1` FROM VALUES ('a'), ('b')""",
             },
         )
+        self.validate_all(
+            "SELECT * FROM (SELECT OBJECT_CONSTRUCT('a', 1) AS x) AS t",
+            read={
+                "duckdb": "SELECT * FROM (VALUES ({'a': 1})) AS t(x)",
+            },
+        )
+        self.validate_all(
+            "SELECT * FROM (SELECT OBJECT_CONSTRUCT('a', 1) AS x UNION ALL SELECT OBJECT_CONSTRUCT('a', 2)) AS t",
+            read={
+                "duckdb": "SELECT * FROM (VALUES ({'a': 1}), ({'a': 2})) AS t(x)",
+            },
+        )
 
     def test_describe_table(self):
         self.validate_all(