Alembic: IntegrityError: "column contains null values" when adding non-nullable column
I'm adding a column to an existing table. This new column is nullable=False.
op.add_column('mytable', sa.Column('mycolumn', sa.String(), nullable=False))
When I run the migration, it complains:
sqlalchemy.exc.IntegrityError: column "mycolumn" contains null valuesIt is because your existing data have no value on that new column, i.e. null. Thus causing said error. When adding a non-nullable column, you must decide what value to give to already-existing data Alright, existing data should just have "lorem ipsum" for this new column then. But how do I do it? I can't UPDATE because the column is not there yet. Use the server_default arg: op.add_column('mytable', sa.Column( 'mycolumn', sa.String(), nullable=False, server_default='lorem ipsum', # <--- add this )) But, but, I don't want it to have default value Drop it afterwards using op.alter_column('mytable', 'mycolumn', server_default=None) E.g. your upgrade() function would be: def upgrade(): op.add_column('mytable', sa.Column('mycolumn', sa.String(), nullable=False, server_default='lorem ipsum')) op.alter_column('mytable', 'mycolumn', server_default=None)
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