There are a variety of issues when using “batch” mode with constraints, The reflection process may also be bypassed entirely by sending a alter_column ( 'flag', new_column_name = 'bflag', existing_type = Boolean ) batch_alter_table ( "bar", reflect_kwargs = dict ( listeners = ) ) as batch_op : batch_op. Object is reflected with the create_constraint flag set to False:ĭef listen_for_reflect ( inspector, table, column_info ): "correct an ENUM type" if column_info = 'my_enum' : column_info = Enum ( 'a', 'b', 'c' ) with self. The reflection process such that a Boolean “move and copy” proceeds is performed using the standard autoload=TrueĪpproach. To run “move and copy” unconditionally in all cases, including on databases Operations.batch_alter_table() can be configured Which is the one kind of column-level ALTER statement that SQLite supports. Migration directives other than Operations.add_column() present, The “move and copy” process if SQLite is in use, and if there are There were no batch directive - the batch context by default only does On other backends, we’d see the usual ALTER statements done as though id FROM some_table DROP TABLE some_table ALTER TABLE _alembic_batch_temp RENAME TO some_table The Operations.batch_alter_table() method provides the gateway to thisĬREATE TABLE _alembic_batch_temp ( id INTEGER NOT NULL, foo INTEGER, PRIMARY KEY ( id ) ) INSERT INTO _alembic_batch_temp ( id ) SELECT some_table. Table is dropped and the new one renamed to the original name. Old table to the new table using “INSERT from SELECT”, and finally the old “move and copy” procedure begins the existing table structure is reflectedįrom the database, a new version of this table is created with the given When the context is complete, a process begins whereby the Mutation operations to that table alone are specified within Within this context, a relational table is named, and then a series of With other databases, Alembic provides the batch operations context. In a way that is reasonably predictable, while also remaining compatible We’ll call this “move and copy” workflow, and in order to accommodate it Table to the new one, then drop the old table. Migration tools are instead expected to produce copies of SQLite tables thatĬorrespond to the new structure, transfer the data from the existing Philosophical and architectural concerns within SQLite, and they are unlikely ![]() In that it has almost no support for the ALTER statement which The SQLite database presents a challenge to migration tools As usual, if you have any questions, just leave a note in the Comments section below.Running “Batch” Migrations for SQLite and Other Databases ¶ I hope these SQLite alter table examples are helpful. INSERT INTO t1 SELECT a,b FROM t1_backup INSERT INTO t1_backup SELECT a,b FROM t1 The following steps illustrate how this could be done:" įor example, suppose you have a table named 't1' with columns names 'a', 'b', and 'c' and that you want to delete column 'c' from this table. if you want to make more complex changes in the structure of a table, you will have to recreate the table. The following text is copied from the SQLite FAQ: Sqlite> alter table order_items rename to line_items More complicated ALTER TABLE examplesĪs the SQLite documentation mentions, there are many things you can’t accomplish with the ALTER TABLE command at this time. ![]() Here's an example to demonstrate this alter table syntax: How to change a database table name with ALTER TABLEĪs mentioned, you can also use the SQLite ALTER TABLE syntax to change the name of an existing database table. You can even go crazy, and specify a type and a default value with the SQLite ALTER TABLE syntax:ĪLTER TABLE test1 ADD COLUMN baz TEXT NOT NULL DEFAULT 'baz' Or you can specify a type, if you prefer: This means that you can also add a new column without specifying its type, like this: ![]() First, create a simple database table to work with:Īs you can see, the SQLite CREATE TABLE syntax is pretty forgiving, and you don't even have to specify the data types of the table columns. ADD COLUMN" syntax, as shown in the following code. You can add a column to an existing SQLite table with the SQLite "ALTER TABLE. Add a column to the end of an existing SQLite database tableįor other changes you'll have to follow some workaround procedures (discussed below).SQLite FAQ: Can you show me how the SQLite ALTER TABLE syntax works?Īt the time of this writing you can use the SQLite ALTER TABLE syntax for two purposes:
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