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From: Josh Berkus <josh@agliodbs.com>
To: Jim Nasby <Jim.Nasby@BlueTreble.com>
To: Peter Geoghegan <peter.geoghegan86@gmail.com>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: working around JSONB's lack of stats?
Date: Sun, 01 Feb 2015 13:08:01 -0800
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On 01/30/2015 05:34 PM, Jim Nasby wrote:
> On 1/30/15 2:26 PM, Josh Berkus wrote:
>> This would probably work because there aren't a lot of data structures
>> where people would have the same key:value pair in different locations
>> in the JSON, and care about it stats-wise.  Alternatetly, if the same
>> key-value pair appears multiple times in the same sample row, we could
>> cut the MC% by that multiple.
> 
> Even if there were multiple occurrences, this would probably still be an
> improvement.
> 
> Another idea... at one time in the past when discussing statistics on
> multiple columns, one idea was to build statistics on indexes. If we
> built that, we could also do the same thing for at least JSONB (not sure
> about JSON). Obviously doesn't help for stuff you haven't indexed, but
> presumably if you care about performance and have any significant size
> of data you've also indexed parts of the JSON, yes?

I'm not clear on what you're suggesting here.  I'm discussing how the
stats for a JSONB field would be stored and accessed; I don't understand
what that has to do with indexing.

-- 
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com


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