On Fri, Jun 25, 2021, at 11:58 AM, mkmo...@gmail.com wrote:
>
> When using PostgreSQL, creating a foreign key on a column in a table does not
> automatically index that column, unlike Oracle or MySQL.
>
> I would like to get SQLAlchemy to automatically create an index on the same
> columns that are specified in a ForeingKeyConstraint.
>
> For example, if I have a table like this:
>
> foo = table(
> 'foos', metadata,
> Column('id', BigInteger),
> Column('parent_id', BigInteger),
> ForeignKeyConstraint(('parent_id',), refcolumns=('bar.id',),
> name='foo_parent_id_fk')
> )
>
> I would like it to automatically add an Index like:
>
> Index('foo_parent_id_idx', 'parent_id')
>
> I've made the following, which appears to work:
>
> from sqlalchemy import event, Table
>
> @event.listens_for(Table, 'before_create')
> def add_index_on_foreign_key_columns(table, connection, **kwargs):
> for foreign_key in table.foreign_key_constraints:
> index_name = foreign_key.name.replace('_fk', '_idx')
> columns = (c.name for c in foreign_key.columns)
> Index(index_name, *columns, _table=table)
>
> Is there a better way to accomplish this?
that's the perfect way to accomplish this and is just what I'd recommend - the
only thing I would change is when creating the Index(), it should auto-add
itself to the Table as you are passing Table-bound Column objects to it, so i
would not use the private "_table" parameter. Otherwise, you can say
"table.append_index(my_index)" to ensure it is added to the Table.
>
> Thanks and best regards,
>
> Matthew Moisen
>
>
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
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SQLAlchemy -
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http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
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