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https://github.com/simonw/sqlite-utils/issues/467#issuecomment-1224385575	https://api.github.com/repos/simonw/sqlite-utils/issues/467	1224385575	IC_kwDOCGYnMM5I-qQn	9599	2022-08-23T17:19:00Z	2022-08-23T17:19:00Z	OWNER	Initial prototype: ```diff diff --git a/sqlite_utils/db.py b/sqlite_utils/db.py index 18a442a..03fd345 100644 --- a/sqlite_utils/db.py +++ b/sqlite_utils/db.py @@ -875,6 +875,7 @@ class Database: hash_id_columns: Optional[Iterable[str]] = None, extracts: Optional[Union[Dict[str, str], List[str]]] = None, if_not_exists: bool = False, + transform: bool = False, ) -> "Table": """ Create a table with the specified name and the specified ``{column_name: type}`` columns. @@ -892,7 +893,39 @@ class Database: :param hash_id_columns: List of columns to be used when calculating the hash ID for a row :param extracts: List or dictionary of columns to be extracted during inserts, see :ref:`python_api_extracts` :param if_not_exists: Use ``CREATE TABLE IF NOT EXISTS`` - """ + :param transform: If table already exists, transform it to fit the specified schema + """ + # Transform table to match the new definition if table already exists: + if transform and self[name].exists(): + # First add missing columns and columns to drop + existing_columns = self[name].columns_dict + missing_columns = dict( + (col_name, col_type) + for col_name, col_type in columns.items() + if col_name not in existing_columns + ) + columns_to_drop = [ + column for column in existing_columns if column not in columns + ] + if missing_columns: + for col_name, col_type in missing_columns.items(): + self[name].add_column(col_name, col_type) + # Do we need to reset the column order? + column_order = None + if list(existing_columns) != list(columns): + column_order = list(columns) + # Only run .transform() if there is something to do + # TODO: this misses changes like pk= without also column changes + if columns_to_drop or missing_columns or column_order: + self[name].transform( + types=columns, + drop=columns_to_drop, + column_order=column_order, + not_null=not_null, + defaults=defaults, + pk=pk, + ) + return cast(Table, self[name]) sql = self.create_table_sql( name=name, columns=columns, @@ -1477,6 +1510,7 @@ class Table(Queryable): hash_id_columns: Optional[Iterable[str]] = None, extracts: Optional[Union[Dict[str, str], List[str]]] = None, if_not_exists: bool = False, + transform: bool = False, ) -> "Table": """ Create a table with the specified columns. @@ -1508,6 +1542,7 @@ class Table(Queryable): hash_id_columns=hash_id_columns, extracts=extracts, if_not_exists=if_not_exists, + transform=transform, ) return self ``` Needs more thought about how things like just a change to `pk=` should work.	{"total_count": 0, "+1": 0, "-1": 0, "laugh": 0, "hooray": 0, "confused": 0, "heart": 0, "rocket": 0, "eyes": 0}	1348169997