From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
Cc: | Mayank Kandari <mayank(dot)kandari(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Query is taking too long i intermittent |
Date: | 2022-06-06 14:11:42 |
Message-ID: | 894424.1654524702@sss.pgh.pa.us |
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Lists: | pgsql-performance |
Justin Pryzby <pryzby(at)telsasoft(dot)com> writes:
> On Mon, Jun 06, 2022 at 03:28:43PM +0530, Mayank Kandari wrote:
>> SELECT event_id FROM event WHERE (event_sec > time.seconds) OR
>> ((event_sec=time.seconds) AND (event_usec>=time.useconds) ORDER BY
>> event_sec, event_usec LIMIT 1
> I think it'd be better if the column was a float storing the fractional number
> of seconds. Currently, it may be hard for the planner to estimate rowcounts if
> the conditions are not independent. I don't know if it's related to this
> problem, though.
Also, even if you can't change the data representation, there's a more
idiomatic way to do that in SQL: use a row comparison.
SELECT ...
WHERE row(event_sec, event_usec) >= row(time.seconds, time.useconds) ...
I doubt this is notably more execution-efficient, but if you're getting a
bad rowcount estimate it should help with that. It's easier to read too.
regards, tom lane
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