From: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
---|---|
To: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
Cc: | Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: computing completion tag is expensive for pgbench -S -M prepared |
Date: | 2018-06-07 10:01:26 |
Message-ID: | CANP8+jL22Y0YwKPGFCaCXuKuHRD=qxFHW=pviPr5aOEH5z84RQ@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On 7 June 2018 at 06:01, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> wrote:
> On 7 June 2018 at 16:13, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> in PortalRun(). That's actually fairly trivial to optimize - we don't
>> need the full blown snprintf machinery here. A quick benchmark
>> replacing it with:
>>
>> memcpy(completionTag, "SELECT ", sizeof("SELECT "));
>> pg_lltoa(nprocessed, completionTag + 7);
>
> I'd also noticed something similar with some recent benchmarks I was
> doing for INSERTs into partitioned tables. In my case I saw as high as
> 0.7% of the time spent building the INSERT tag. So I think it's worth
> fixing this.
>
> I think it would be better to invent a function that accepts a
> CmdType, int64 and Oid that copies the tag into the supplied buffer,
> then make a more generic change that also replaces the code in
> ProcessQuery() which builds the tag. I'm sure there must be some way
> to get the CmdType down to the place you've patched so we can get rid
> of the if (strcmp(portal->commandTag, "SELECT") == 0) line too.
Sounds better
Do we actually need the completion tag at all? In most cases??
Perhaps we should add a parameter to make it optional and turn it off
by default, except for psql.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
From | Date | Subject | |
---|---|---|---|
Next Message | Daniel Gustafsson | 2018-06-07 10:28:24 | Typo in planner README |
Previous Message | Amit Langote | 2018-06-07 09:37:18 | Re: Needless additional partition check in INSERT? |