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Date: Wed, 9 Apr 2014 01:40:39 -0700
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 <CAM3SWZQbjqippSdQU2RHFTOe_SyoMcH_MOCcUeYPA0NWPjYqLQ@mail.gmail.com>
Subject: Re: default opclass for jsonb (was Re: Call for
 GIST/GIN/SP-GIST opclass documentation)
From: Peter Geoghegan <pg@heroku.com>
To: Heikki Linnakangas <hlinnakangas@vmware.com>
Cc: Andrew Dunstan <andrew@dunslane.net>, Tom Lane <tgl@sss.pgh.pa.us>,
 pgsql-hackers@postgresql.org
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On Wed, Apr 9, 2014 at 1:21 AM, Heikki Linnakangas
<hlinnakangas@vmware.com> wrote:
> I didn't say that. On the contrary, I think the shotgun approach jsonb_ops
> and jsonb_hash_ops take is too broad. It should be possible to specify what
> to index in a more detailed fashion.

It is - use an expression index. That's by far the most important way
to specify what to index in a more detailed fashion. There are others,
but that's the major one. Beyond that, yes, it's necessary to
carefully write your query predicate a certain way. However, a similar
situation exists in MongoDB, where there is a distinction between
"Indexes on embedded fields" (which must be accessed using special
"dot notation") and "indexes on subdocuments" (which cannot be
accessed using "dot notation"). It's late here, but I'm pretty sure
that's a feature and not a limitation.


-- 
Peter Geoghegan


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