Hi Mike,
Thanks for your feedback. I'll leave your suggestion here if anyone comes
across this:
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 <http://c.name> for c in foreign_key.columns)
Index(index_name, *columns)
Best regards,
Matthew Moisen
On Friday, June 25, 2021 at 9:58:56 AM UTC-7 Mike Bayer wrote:
>
>
> On Fri, Jun 25, 2021, at 11:58 AM, [email protected] 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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