Re: Collect frequency statistics for arrays

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alexander Korotkov <aekorotkov(at)gmail(dot)com>
Cc: Noah Misch <noah(at)leadboat(dot)com>, Nathan Boley <npboley(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Collect frequency statistics for arrays
Date: 2012-03-04 20:41:37
Message-ID: 4826.1330893697@sss.pgh.pa.us
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Alexander Korotkov <aekorotkov(at)gmail(dot)com> writes:
> On Sun, Mar 4, 2012 at 5:38 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> 1. I'm still unhappy about the loop that fills the count histogram,
>> as I noted earlier today. It at least needs a decent comment and some
>> overflow protection, and I'm not entirely convinced that it doesn't have
>> more bugs than the overflow issue.

> Attached patch is focused on fixing this. The "frac" variable overflow is
> evaded by making it int64. I hope comments is clarifying something. In
> general this loop copies behaviour of histogram constructing loop of
> compute_scalar_stats function. But instead of values array we've array of
> unique DEC and it's frequency.

OK, I reworked this a bit and committed it. Thanks.

regards, tom lane

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