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Re: Collect frequency statistics for arrays

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Nathan Boley <npboley(at)gmail(dot)com>
Cc: Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Collect frequency statistics for arrays
Date: 2012-02-29 23:10:44
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Nathan Boley <npboley(at)gmail(dot)com> writes:
> On Wed, Feb 29, 2012 at 2:43 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Nathan Boley <npboley(at)gmail(dot)com> writes:
>>> If I understand you're suggestion, queries of the form
>>> SELECT * FROM rel
>>> WHERE ARRAY[ 1,2,3,4 ] <= x
>>>   AND x <=ARRAY[ 1, 2, 3, 1000];
>>> would no longer use an index. Is that correct?

>> No, just that we'd no longer have statistics relevant to that, and would
>> have to fall back on default selectivity assumptions.

> Which, currently, would mean queries of that form would typically use
> a table scan, right?

No, it doesn't.

> What about MCV's? Will those be removed as well?

Sure.  Those seem even less useful.

			regards, tom lane

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