id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
5806	Would like a callback on models.Field during SQL generation	sam@…	nobody	"It would be useful if Fields had the opportunity to specify SQL code to be included when generating the SQL for their model.

I am currently trying to add some stuff to the SQL generated by Django to implement full text indexes in PostgreSQL for several models. Each model requires the following to be added:

{{{
-- full text indexing on blogs_post
CREATE INDEX blogs_post_fts
    ON blogs_post
    USING gin
    (vector);
CREATE FUNCTION blogs_post_fts_update () RETURNS trigger AS $$
BEGIN
    NEW.vector = ts2.to_tsvector ('default', NEW.title || ' ' || NEW.body);
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER blogs_post_fts_update BEFORE INSERT OR UPDATE ON blogs_post FOR EACH
ROW EXECUTE PROCEDURE blogs_post_fts_update ();
-- end of full text indexing on blogs_post
}}}

Entering this for every table that I want to create an index upon is really annoying!

It is possible to generate these SQL statements based on information in the model definition:

{{{
class Blog (models.Model):
   title = models.TextField ()
   body = models.TextField ()
   vector = TsvectorField (fields = ['title', 'body'])
}}}

In order to do this, I created a custom field type that adds the actual field to the CREATE TABLE statement:

{{{
class TsvectorField (models.Field):
    def __init__ (self, fields, *args, **kwargs):
        if kwargs.pop ('editable', False) == True:
            raise ValueError ('TsvectorFields can not be editable')
        super (TsvectorField, self).__init__ (*args, **kwargs)

        # do something with fields!

    def db_type (self):
        return 'ts2.tsvector'
}}}

But at this point I am stuck: as far as I can see, there is nowhere to place the code to generate the above SQL.

I propose that `django.core.management.sql.sql_indexes_for_model` by modified to call a method on each field, named something like `get_sql_index`. This method would generate & return the above SQL statements.

Thoughts?"		closed	Uncategorized	dev		wontfix			Unreviewed	0	0	0	0	0	0