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Date: Tue, 8 Apr 2014 14:57:44 -0700
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Subject: Re: default opclass for jsonb (was Re: Call for
 GIST/GIN/SP-GIST opclass documentation)
From: Peter Geoghegan <pg@heroku.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@postgresql.org
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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.

-- 
Peter Geoghegan


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