Patch/alter-column-optimized-merged-patched

dbt/adapters/sqlserver/sqlserver_adapter.py

@@ -113,6 +113,17 @@ def _behavior_flags(self) -> List[dict]:
         by the BaseAdapter.behavior machinery.
         """
         return [
+            {
+                "name": "sqlserver__prefer_single_alter_column",
+                "default": False,
+                "source": "dbt-sqlserver",
+                "description": (
+                    "If true, prefer running a single "
+                    "ALTER ... ALTER COLUMN for type expansions on tables. When false, "
+                    "fall back to add/copy/drop/rename flow."
+                ),
+                "docs_url": None,
+            },
             {
                 "name": "enable_safe_type_expansion",
                 "default": False,

dbt/include/sqlserver/macros/adapter/columns.sql

@@ -24,27 +24,34 @@
 {% endmacro %}
 
 {% macro sqlserver__alter_column_type(relation, column_name, new_column_type) %}
-
-    {%- set tmp_column = column_name + "__dbt_alter" -%}
-    {% set alter_column_type %}
-        alter {{ relation.type }} {{ relation }} add "{{ tmp_column }}" {{ new_column_type }};
-    {%- endset %}
-
-    {% set update_column %}
-        update {{ relation }} set "{{ tmp_column }}" = "{{ column_name }}";
-    {%- endset %}
-
-    {% set drop_column %}
-        alter {{ relation.type }} {{ relation }} drop column "{{ column_name }}";
-    {%- endset %}
-
-    {% set rename_column %}
-        exec sp_rename '{{ relation | replace('"', '') }}.{{ tmp_column }}', '{{ column_name }}', 'column'
-    {%- endset %}
-
-    {% do run_query(alter_column_type) %}
-    {% do run_query(update_column) %}
-    {% do run_query(drop_column) %}
-    {% do run_query(rename_column) %}
-
-{% endmacro %}
+    {% if flags.sqlserver__prefer_single_alter_column and relation.type == 'table' %}
+        {% set alter_column_type_sql %}
+            alter {{ relation.type }} {{ relation }} alter column "{{ column_name }}" {{ new_column_type }};
+        {%- endset %}
+
+        {% do run_query(alter_column_type_sql) %}
+    {% else %}
+        {%- set tmp_column = column_name + "__dbt_alter" -%}
+
+        {% set alter_column_type %}
+            alter {{ relation.type }} {{ relation }} add "{{ tmp_column }}" {{ new_column_type }};
+        {%- endset %}
+
+        {% set update_column %}
+            update {{ relation }} set "{{ tmp_column }}" = "{{ column_name }}";
+        {%- endset %}
+
+        {% set drop_column %}
+            alter {{ relation.type }} {{ relation }} drop column "{{ column_name }}";
+        {%- endset %}
+
+        {% set rename_column %}
+            exec sp_rename '{{ relation | replace('"', '') }}.{{ tmp_column }}', '{{ column_name }}', 'column'
+        {%- endset %}
+
+        {% do run_query(alter_column_type) %}
+        {% do run_query(update_column) %}
+        {% do run_query(drop_column) %}
+        {% do run_query(rename_column) %}
+    {% endif %}
+ {% endmacro %}