fix(snowflake): use ALTER ICEBERG TABLE to register column comments on Iceberg tables

Snowflake rejects `ALTER TABLE` for Iceberg tables and requires
`ALTER ICEBERG TABLE` instead. `SnowflakeEngineAdapter._create_column_comments`
builds its statement with a hardcoded `TABLE` kind, so registering column
comments on an Iceberg table with a post-creation command emitted
`ALTER TABLE ... ALTER COLUMN ... COMMENT`. The failure is swallowed and
logged as a permissions warning, so the comments were silently dropped.

This path is only taken when the comments can't be inlined into the CTAS
schema definition, i.e. when the column types are not fully known.

`_create_column_comments` now accepts `table_format`, mirroring the
`_create_table` convention, and the base adapter passes it from the two
table creation paths. The Snowflake adapter derives the Iceberg-specific
table kind from it.

Follow-up to #5722. Related: #5721

Signed-off-by: Guillem G <guillem.gimenez@titanos.tv>

Author: sineline

sqlmesh/core/engine_adapter/base.py

@@ -833,7 +833,9 @@ def _create_table_from_columns(
             and self.COMMENT_CREATION_TABLE.is_comment_command_only
             and self.comments_enabled
         ):
-            self._create_column_comments(table_name, column_descriptions)
+            self._create_column_comments(
+                table_name, column_descriptions, table_format=kwargs.get("table_format")
+            )
 
     def _build_schema_exp(
         self,
@@ -990,7 +992,9 @@ def _create_table_from_source_queries(
         ):
             self._create_table_comment(table_name, table_description)
         if column_descriptions and schema is None and self.comments_enabled:
-            self._create_column_comments(table_name, column_descriptions)
+            self._create_column_comments(
+                table_name, column_descriptions, table_format=kwargs.get("table_format")
+            )
 
     def _create_table(
         self,
@@ -3058,7 +3062,18 @@ def _create_column_comments(
         column_comments: t.Dict[str, str],
         table_kind: str = "TABLE",
         materialized_view: bool = False,
+        table_format: t.Optional[str] = None,
     ) -> None:
+        """Registers column comments with a post-creation command.
+
+        Args:
+            table_name: The name of the table or view.
+            column_comments: Mapping between the column name and its comment.
+            table_kind: The kind of object being commented on, `TABLE` or `VIEW`.
+            materialized_view: Whether the view is materialized.
+            table_format: The table format of the table, if any. Engines that require
+                format-specific DDL to alter a table use it to derive `table_kind`.
+        """
         table = exp.to_table(table_name)
 
         for col, comment in column_comments.items():

sqlmesh/core/engine_adapter/bigquery.py

@@ -818,6 +818,7 @@ def _create_column_comments(
         column_comments: t.Dict[str, str],
         table_kind: str = "TABLE",
         materialized_view: bool = False,
+        table_format: t.Optional[str] = None,
     ) -> None:
         if not (table_kind == "VIEW" and materialized_view):
             table = self._get_table(table_name)

sqlmesh/core/engine_adapter/mysql.py

@@ -131,6 +131,7 @@ def _create_column_comments(
         column_comments: t.Dict[str, str],
         table_kind: str = "TABLE",
         materialized_view: bool = False,
+        table_format: t.Optional[str] = None,
     ) -> None:
         table = exp.to_table(table_name)
         table_sql = table.sql(dialect=self.dialect, identify=True)

sqlmesh/core/engine_adapter/snowflake.py

@@ -632,13 +632,20 @@ def _create_column_comments(
         column_comments: t.Dict[str, str],
         table_kind: str = "TABLE",
         materialized_view: bool = False,
+        table_format: t.Optional[str] = None,
     ) -> None:
         """
         Reference: https://docs.snowflake.com/en/sql-reference/sql/alter-table-column#syntax
+        Reference: https://docs.snowflake.com/en/sql-reference/sql/alter-iceberg-table#syntax
         """
         if not column_comments:
             return
 
+        # Snowflake rejects `ALTER TABLE` for Iceberg tables, it requires
+        # `ALTER ICEBERG TABLE` instead
+        if table_format and table_kind == "TABLE":
+            table_kind = f"{table_format.upper()} TABLE"
+
         table = exp.to_table(table_name)
         table_sql = self._to_sql(table)
 

tests/core/engine_adapter/test_snowflake.py

@@ -246,6 +246,38 @@ def test_multiple_column_comments(make_mocked_engine_adapter: t.Callable, mocker
     ]
 
 
+def test_column_comments_iceberg(make_mocked_engine_adapter: t.Callable):
+    adapter = make_mocked_engine_adapter(SnowflakeEngineAdapter)
+
+    adapter._create_column_comments(
+        "test_table",
+        {"a": "a column description", "b": "b column description"},
+        table_format="iceberg",
+    )
+
+    assert to_sql_calls(adapter) == [
+        """ALTER ICEBERG TABLE "test_table" ALTER COLUMN "a" COMMENT 'a column description', COLUMN "b" COMMENT 'b column description'""",
+    ]
+
+
+def test_ctas_column_comments_iceberg(make_mocked_engine_adapter: t.Callable):
+    adapter = make_mocked_engine_adapter(SnowflakeEngineAdapter)
+
+    # The column types are unknown, so the comments can't be inlined into the CTAS
+    # schema definition and are registered with a post-creation ALTER instead
+    adapter.ctas(
+        "test_table",
+        parse_one("SELECT a, b FROM source_table"),
+        table_format="iceberg",
+        column_descriptions={"a": "a column description"},
+    )
+
+    assert to_sql_calls(adapter) == [
+        """CREATE ICEBERG TABLE IF NOT EXISTS "test_table" AS SELECT "a", "b" FROM "source_table\"""",
+        """ALTER ICEBERG TABLE "test_table" ALTER COLUMN "a" COMMENT 'a column description'""",
+    ]
+
+
 def test_sync_grants_config(make_mocked_engine_adapter: t.Callable, mocker: MockerFixture):
     adapter = make_mocked_engine_adapter(SnowflakeEngineAdapter)
     relation = normalize_identifiers(