public inbox for [email protected]
help / color / mirror / Atom feedFrom: Andrei Lepikhov <[email protected]>
To: Ilia Evdokimov <[email protected]>
To: David Rowley <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Lukas Fittl <[email protected]>
Cc: Daniel Gustafsson <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: Nikolay Samokhvalov <[email protected]>
Subject: Re: Add estimated hit ratio to Memoize in EXPLAIN to explain cost adjustment
Date: Mon, 7 Jul 2025 15:49:58 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <CAP53Pky29GWAVVk3oBgKBDqhND0BRBN6yTPeguV_qSivFL5N_g@mail.gmail.com>
<[email protected]>
<[email protected]>
<[email protected]>
<CAApHDvpT0Y1BfYgeWz+PkKaLBEff1izYOAjNSibhBTNFEdqLtg@mail.gmail.com>
<CA+TgmobDHmaNTqi5yLPJoW6fTCuiWOgF9CSCSHX_OTLmGxYRUQ@mail.gmail.com>
<CAApHDvqYL3OVvOsyvEPsDJ7h4zQh=LEygQgcQSN-TemRJLMb6Q@mail.gmail.com>
<[email protected]>
<CAApHDvpuM8jW-BGu7B=i6uv+jmndEo-2z_BYvj5JNmx=qV-uSQ@mail.gmail.com>
<[email protected]>
<CAApHDvqmyHuEt7rdFLJr4cZecbhno5OZ6iL5EQNNu9Oi1f93sQ@mail.gmail.com>
<[email protected]>
<CAApHDvq0Zz3+nh9hPRBP-oAocFZETfhdE_jcN8aG+Thc24Zk5g@mail.gmail.com>
<[email protected]>
<[email protected]>
<[email protected]>
On 4/7/2025 10:30, Ilia Evdokimov wrote:
> On 01.05.2025 15:22, Ilia Evdokimov wrote:
>
>> I attached updated v9 patch with the suggested changes. The updated
>> line in the EXPLAIN looks like this:
>>
>> Text format:
>> Estimates: capacity=1 distinct keys=1 lookups=2 hit percent=50.00%
>>
>> Non-text format:
>> Estimated Capacity: 1
>> Estimated Distinct Lookup Keys: 1
>> Estimated Lookups: 2
>> Estimated Hit Percent: 50.00
>>
>> Any suggestions?
>
>
> I attached rebased v10 patch on 5a6c39b.
Exposing internal information about the estimation of the number of
groups in the Memoise node, shouldn't we do the same in even more vague
cases, such as IncrementalSort? For example, in [1] (see its
attachment), I observe that IncrementalSort is considerably better than
Sort, but has a larger cost. It would be helpful to understand if an
incorrect ngroups estimation causes this.
[1]
https://www.postgresql.org/message-id/[email protected]
--
regards, Andrei Lepikhov
view thread (53+ messages) latest in thread
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
Subject: Re: Add estimated hit ratio to Memoize in EXPLAIN to explain cost adjustment
In-Reply-To: <[email protected]>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox