feat: In SQL targets, users can now disable column type alterations w…

…ith the `allow_column_alter` built-in setting

singer_sdk/connectors/sql.py

@@ -17,6 +17,7 @@
 from singer_sdk import typing as th
 from singer_sdk._singerlib import CatalogEntry, MetadataMapping, Schema
 from singer_sdk.exceptions import ConfigValidationError
+from singer_sdk.helpers._builtin_setting import BuiltinSetting
 from singer_sdk.helpers.capabilities import TargetLoadMethods
 
 if t.TYPE_CHECKING:
@@ -39,7 +40,10 @@ class SQLConnector:  # noqa: PLR0904
 
     allow_column_add: bool = True  # Whether ADD COLUMN is supported.
     allow_column_rename: bool = True  # Whether RENAME COLUMN is supported.
-    allow_column_alter: bool = False  # Whether altering column types is supported.
+
+    #: Whether altering column types is supported.
+    allow_column_alter = BuiltinSetting(default=True)
+
     allow_merge_upsert: bool = False  # Whether MERGE UPSERT is supported.
     allow_overwrite: bool = False  # Whether overwrite load method is supported.
     allow_temp_tables: bool = True  # Whether temp tables are supported.

singer_sdk/helpers/capabilities.py

@@ -159,6 +159,13 @@
         description="Maximum number of rows in each batch.",
     ),
 ).to_dict()
+TARGET_ALLOW_COLUMN_ALTER_CONFIG = PropertiesList(
+    Property(
+        "allow_column_alter",
+        BooleanType,
+        description="Allow altering columns in the target database.",
+    ),
+).to_dict()
 
 
 class TargetLoadMethods(str, Enum):

singer_sdk/target_base.py

@@ -18,6 +18,7 @@
 from singer_sdk.helpers.capabilities import (
     ADD_RECORD_METADATA_CONFIG,
     BATCH_CONFIG,
+    TARGET_ALLOW_COLUMN_ALTER_CONFIG,
     TARGET_BATCH_SIZE_ROWS_CONFIG,
     TARGET_HARD_DELETE_CONFIG,
     TARGET_LOAD_METHOD_CONFIG,
@@ -685,6 +686,8 @@ def _merge_missing(source_jsonschema: dict, target_jsonschema: dict) -> None:
                 if k not in target_jsonschema["properties"]:
                     target_jsonschema["properties"][k] = v
 
+        _merge_missing(TARGET_ALLOW_COLUMN_ALTER_CONFIG, config_jsonschema)
+
         capabilities = cls.capabilities
 
         if TargetCapabilities.TARGET_SCHEMA in capabilities:

tests/core/targets/test_target_sql.py

@@ -48,6 +48,7 @@ class MyTarget(SQLTargetMock, capabilities=capabilities):
     about = MyTarget._get_about_info()
     default_settings = {
         "add_record_metadata",
+        "allow_column_alter",
         "load_method",
         "batch_size_rows",
     }