| 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: | 26664.1330557044@sss.pgh.pa.us |
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| 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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