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Date: Tue, 8 Apr 2014 14:03:46 -0700
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 <CAM3SWZQGZyqSBzaFZ4gmtnQZpcXLE=ceUL_O29gtMgnP=AvC+g@mail.gmail.com>
Subject: 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, pgsql-docs@postgresql.org
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On Tue, Apr 8, 2014 at 1:41 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I just created sections in the SGML manual chapters about GIST, GIN, and
> SP-GIST to hold documentation about the standard opclasses provided for
> them:

I think that that's a good idea. I too was bothered by this omission.

>     Of the two operator classes for type jsonb, jsonb_ops is the
>     default. jsonb_hash_ops supports fewer operators but will work with
>     larger indexed values than jsonb_ops can support.
>
> Is that accurate?  Do we need to say more?

Well, I'm not sure that it's worth noting there, but as you probably
already know jsonb_hash_ops will perform a lot better than the default
GIN opclass, and will have much smaller indexes. FWIW I think that the
size limitation is overblown, and performance is in fact the
compelling reason to prefer jsonb_hash_ops, although it's probably
incongruous to explain the issues that way in this section of the
docs. It probably suffices that that is covered in the "JSON Types"
section.

-- 
Peter Geoghegan


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