counter_cache is making a redundant SELECT before UPDATE

rubyonrails-talk
1

Hmm, actually I just watched the railscasts about the counter_cache, and in his log he also has this redundant SELECT that he didn't even spot.

So I guess this could be an additional feature added to Rails to save 1 DB query.

2

Hmm, actually I just watched the railscasts about the counter_cache, and in his log he also has this redundant SELECT that he didn't even spot.

So I guess this could be an additional feature added to Rails to save 1 DB query.

This is basically rails not knowing about inverse associations (which it will do in the next version). If you do do itself you should use increment_counter rather that doing what you show above (which has a race condition).

Fred

3

This is basically rails not knowing about inverse associations (which it will do in the next version). If you do do itself you should use increment_counter rather that doing what you show above (which has a race condition).

Fred

Thank you Frederick for your message :slight_smile:

4

Quoting Fernando Perez <rails-mailing-list@andreas-s.net>:

Hmm, actually I just watched the railscasts about the counter_cache, and in his log he also has this redundant SELECT that he didn't even spot.

So I guess this could be an additional feature added to Rails to save 1 DB query.

Is the title declared unique? Then Rails queries the DB to check that there is no existing record before doing the UPDATE.

HTH,   Jeffrey