Re: default opclass for jsonb (was Re: Call for GIST/GIN/SP-GIST opclass documentation)

On Tue, Apr 8, 2014 at 2:46 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Well, let me see if I understand the situation correctly:
>
> * jsonb_ops supports more operators
>
> * jsonb_hash_ops produces smaller, better-performing indexes
>
> * jsonb_ops falls over on inputs with wide field values, but
> jsonb_hash_ops does not

There might be some compelling cases for indexing existence rather
than containment, since the recheck flag isn't set there, but in
general this summary seems sound. I would say that broadly, existence
is a less useful operator than containment, and so jsonb_hash_ops is
broadly more compelling. I didn't propose changing the default due to
concerns about the POLA, but I'm happy to be told that those concerns
were out of proportion to the practical benefits of a different
default.

--
Peter Geoghegan