Comment registration support for MSSQL engine

docs/concepts/models/overview.md

@@ -184,7 +184,7 @@ This table lists each engine's support for `TABLE` and `VIEW` object comments:
 | DuckDB <=0.9  | N                | N               |
 | DuckDB >=0.10 | Y                | Y               |
 | MySQL         | Y                | Y               |
-| MSSQL         | N                | N               |
+| MSSQL         | Y                | Y               |
 | Postgres      | Y                | Y               |
 | GCP Postgres  | Y                | Y               |
 | Redshift      | Y                | N               |

sqlmesh/core/engine_adapter/mssql.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+from textwrap import dedent
 import typing as t
 import logging
 
@@ -53,8 +54,8 @@ class MSSQLEngineAdapter(
     SUPPORTS_TUPLE_IN = False
     SUPPORTS_MATERIALIZED_VIEWS = False
     CURRENT_CATALOG_EXPRESSION = exp.func("db_name")
-    COMMENT_CREATION_TABLE = CommentCreationTable.UNSUPPORTED
-    COMMENT_CREATION_VIEW = CommentCreationView.UNSUPPORTED
+    COMMENT_CREATION_TABLE = CommentCreationTable.COMMENT_COMMAND_ONLY
+    COMMENT_CREATION_VIEW = CommentCreationView.COMMENT_COMMAND_ONLY
     SUPPORTS_REPLACE_TABLE = False
     MAX_IDENTIFIER_LENGTH = 128
     SUPPORTS_QUERY_EXECUTION_TRACKING = True
@@ -457,3 +458,75 @@ def delete_from(self, table_name: TableName, where: t.Union[str, exp.Expr]) -> N
             )
 
         return super().delete_from(table_name, where)
+
+    def _build_create_comment_table_exp(
+        self, table: exp.Table, table_comment: str, table_kind: str
+    ) -> exp.Comment | str:
+        template = dedent("""
+            DECLARE @comment sql_variant = {comment};
+            DECLARE @property_name VARCHAR(128) = 'MS_Description';
+            DECLARE @schema_name VARCHAR(128) = '{schema_name}';
+            DECLARE @object_name VARCHAR(128) = '{object_name}';
+            DECLARE @object_kind VARCHAR(128) = '{object_kind}';
+            DECLARE @existing sql_variant;
+
+            SELECT TOP 1 @existing = CAST(VALUE AS NVARCHAR) FROM fn_listextendedproperty(@property_name, 'schema', @schema_name, @object_kind, @object_name, DEFAULT, DEFAULT);
+
+            IF @comment IS NULL
+                BEGIN
+                    IF @existing IS NOT NULL
+                        EXEC sp_dropextendedproperty @property_name, 'schema', @schema_name, @object_kind, @object_name;
+                END
+            ELSE
+                BEGIN
+                    IF @existing IS NULL
+                        EXEC sp_addextendedproperty @property_name,@comment, 'schema', @schema_name, @object_kind, @object_name;
+                    ELSE IF @existing != @comment
+                        EXEC sp_updateextendedproperty @property_name, @comment, 'schema', @schema_name, @object_kind, @object_name;
+                END
+        """)
+        tsql_text = template.format(
+            comment = exp.Literal.string(table_comment).sql(dialect=self.dialect) if table_comment is not None else "NULL",
+            schema_name = table.db if table.db else "dbo",
+            object_name = table.name,
+            object_kind = table_kind,
+        )
+        return tsql_text
+
+    def _build_create_comment_column_exp(
+        self, table: exp.Table, column_name: str, column_comment: str, table_kind: str
+    ) -> exp.Comment | str:
+
+        template = dedent("""
+            DECLARE @comment sql_variant = {comment};
+            DECLARE @property_name VARCHAR(128) = 'MS_Description';
+            DECLARE @schema_name VARCHAR(128) = '{schema_name}';
+            DECLARE @object_name VARCHAR(128) = '{object_name}';
+            DECLARE @object_kind VARCHAR(128) = '{object_kind}';
+            DECLARE @column_name VARCHAR(128) = '{column_name}';
+            DECLARE @existing sql_variant;
+
+            SELECT TOP 1 @existing = CAST(VALUE AS NVARCHAR) FROM fn_listextendedproperty(@property_name, 'schema', @schema_name, @object_kind, @object_name, 'column', @column_name);
+
+            IF @comment IS NULL
+                BEGIN
+                    IF @existing IS NOT NULL
+                        EXEC sp_dropextendedproperty @property_name, 'schema', @schema_name, @object_kind, @object_name, 'column', @column_name;
+                END
+            ELSE
+                BEGIN
+                    IF @existing IS NULL
+                        EXEC sp_addextendedproperty @property_name,@comment, 'schema', @schema_name, @object_kind, @object_name, 'column', @column_name;
+                    ELSE IF @existing != @comment
+                        EXEC sp_updateextendedproperty @property_name, @comment, 'schema', @schema_name, @object_kind, @object_name, 'column', @column_name;
+                END
+        """)
+        tsql_text = template.format(
+            comment = exp.Literal.string(column_comment).sql(dialect=self.dialect) if column_comment is not None else "NULL",
+            schema_name = table.db if table.db else "dbo",
+            object_name = table.name,
+            object_kind = table_kind,
+            column_name = column_name,
+        )
+
+        return tsql_text

tests/core/engine_adapter/integration/__init__.py

@@ -526,6 +526,14 @@ def get_table_comment(
                     AND c.relkind = '{"v" if table_kind == "VIEW" else "r"}'
                 ;
             """
+        elif self.dialect == "tsql":
+            kind = "table" if table_kind == "BASE TABLE" else "view"
+            query = f"""
+                SELECT 
+                	ep.name,
+                    CAST(ep.value AS NVARCHAR(MAX)) comment 
+                FROM fn_listextendedproperty('MS_Description', 'schema', '{schema_name}', '{kind}', '{table_name}', DEFAULT, DEFAULT) ep
+            """
 
         result = self.engine_adapter.fetchall(query)
 
@@ -636,6 +644,16 @@ def get_column_comments(
                     AND c.relkind = '{"v" if table_kind == "VIEW" else "r"}'
                 ;
             """
+        elif self.dialect == "tsql":
+            kind = "table" if table_kind == "BASE TABLE" else "view"
+            query = f"""
+                SELECT
+                    col.COLUMN_NAME column_name,
+                    CAST(ep.value AS NVARCHAR(MAX)) comment 
+                FROM INFORMATION_SCHEMA.COLUMNS col
+                CROSS APPLY fn_listextendedproperty('MS_Description', 'schema', col.TABLE_SCHEMA, '{kind}', col.TABLE_NAME, 'column', col.COLUMN_NAME) ep
+                WHERE col.TABLE_SCHEMA = '{schema_name}' AND col.TABLE_NAME = '{table_name}'
+            """
 
         result = self.engine_adapter.fetchall(query)