| From: | ZizhuanLiu X-MAN <44973863(at)qq(dot)com> |
|---|---|
| To: | Ilia Evdokimov <ilya(dot)evdokimov(at)tantorlabs(dot)com>, Damil Shahzad <shahzaddamil(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | pgsql-hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Fix var_eq_const: sum selectivity of all matching MCV entries instead of stopping at first match |
| Date: | 2026-08-05 10:44:46 |
| Message-ID: | tencent_44887C535AD252F33762C013B721D08E4D0A@qq.com |
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| Lists: | pgsql-hackers |
Original
>From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
>Date: 2026-07-30 21:39
>To: ZizhuanLiu X-MAN <44973863(at)qq(dot)com>
>Cc: pgsql-hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
>Subject: Re: Fix var_eq_const: sum selectivity of all matching MCV entries instead of stopping at first match
>I think you need a far stronger
>argument for changing the existing tradeoff than "I believe".
Although I have made efforts to implement it, there is still
no satisfactory and acceptable solution available at present.
>That would double the function's runtime on average, without changing
>the results at all in most cases (it could only be different if the
>given operator has different semantics from the equality operator used
>while building the statistics list).
So I agree with Tom’s reasoning.
regards,
--
ZizhuanLiu (X-MAN)
44973863(at)qq(dot)com
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