On 04/08/2014 05:57 PM, Peter Geoghegan wrote:
> On Tue, Apr 8, 2014 at 2:46 PM, Tom Lane <tgl@sss.pgh.pa.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.
>
I tend to agree with Tom that POLA will be more violated by the default
ops class not being able to index some values.
cheers
andrew
