From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | James Coleman <jtc331(at)gmail(dot)com> |
Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: printf ordering issues? |
Date: | 2018-12-12 00:26:12 |
Message-ID: | 26492.1544574372@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
James Coleman <jtc331(at)gmail(dot)com> writes:
> While using printf to do some good old fashioned print debugging, I
> noticed that it seemed like my printf statements in the executor were
> sometimes not getting printed to the log at all, and sometimes getting
> printed out *before* the ones I have in the planner.
> Upon further investigation I realized instead that the output from the
> executor is getting flushed on the *subsequent* query.
> Is there some kind of weird behavior that most hackers already know
> about and I'm missing?
stdout is usually fully buffered, stderr usually is only line-buffered,
so if you print to stdout you need a lot of fflush'es to keep it in
sync with error/log messages (which go through stderr). Personally
I've developed the habit of just making quick-log logging patches
print to stderr instead ...
regards, tom lane
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