From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
cc: Alvaro Herrera <alvherre@2ndquadrant.com>,
        Simon Riggs <simon@2ndquadrant.com>,
        Andrew Dunstan <andrew.dunstan@2ndquadrant.com>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>,
        Dean Rasheed <dean.a.rasheed@gmail.com>
Subject: Re: WITH clause in CREATE STATISTICS
In-reply-to: <b6b1f3a1-281a-20bc-d961-60604046c73d@2ndquadrant.com>
References: <20170511221330.5akgbsoyx6wm4u34@alvherre.pgsql>
 <22676.1494557205@sss.pgh.pa.us>
 <b6b1f3a1-281a-20bc-d961-60604046c73d@2ndquadrant.com>
Comments: In-reply-to Tomas Vondra <tomas.vondra@2ndquadrant.com>
	message dated "Fri, 12 May 2017 13:13:27 +0200"
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Date: Fri, 12 May 2017 10:05:27 -0400
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Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
> On 5/12/17 4:46 AM, Tom Lane wrote:
>> If people agree that that reads better, we should make an effort to
>> propagate that terminology elsewhere in the docs, and into error messages,
>> objectaddress.c output, etc.

> I'm fine with the 'statistics object' wording. I've been struggling with 
> this bit while working on the patch, and I agree it sounds better and 
> getting it consistent is definitely worthwhile.

OK.  We can work on that as a followon patch.

>> Although I've not done anything about it here, I'm not happy about the
>> handling of dependencies for stats objects.

> Yeah, it's a bit frankensteinian ...

I'm prepared to create a fix for that, but it'd be easier to commit the
current patch first, to avoid merge conflicts.

>> Lastly, I tried the example given in the CREATE STATISTICS reference page,
>> and it doesn't seem to work.

> I assume you're talking about the functional dependencies and in that 
> case that's expected behavior, because f. dependencies do assume the 
> conditions are "consistent" with the functional dependencies.

Hm.  OK, but then that example is pretty misleading, because it leads
the reader to suppose that the planner can tell the difference between
the selectivities of the two queries.  Maybe what's lacking is an
explanation of how you'd use this statistics type.

			regards, tom lane


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