From: Tom Lane <tgl@sss.pgh.pa.us>
To: pgsql-hackers@lists.postgresql.org
Subject: Questionable ping logic in LogicalRepApplyLoop
Date: Fri, 04 Sep 2020 15:41:16 -0400
Message-ID: <959627.1599248476@sss.pgh.pa.us> (raw)
While playing around with clang's scan-build I noticed this warning:
worker.c:2281:7: warning: Value stored to 'ping_sent' is never read
ping_sent = true;
^ ~~~~
At first I thought it was a harmless unnecessary update, but looking
closer I wonder whether it isn't telling us there is a logic bug here.
Specifically, I wonder why the "ping_sent" variable is local to the
loop starting at line 2084, rather than having the same lifespan as
"last_recv_timestamp". Do we really want to forget that we sent a
ping anytime we have to wait for more data?
In fact, looking closer, it appears to me that
(1) The "ping_sent = false" at line 2124 is also dead code, because
ping_sent could never be anything but false at this point;
(2) The "if (!ping_sent)" at line 2274 is also dead code, because
ping_sent is still never anything but false at that point.
In short, we could remove the ping_sent variable entirely without
changing this code's behavior. I'm not 100% sure what semantics
it's trying to achieve, but I don't think it's achieving them.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, pgsql-hackers@lists.postgresql.org
Subject: Re: Questionable ping logic in LogicalRepApplyLoop
In-Reply-To: <959627.1599248476@sss.pgh.pa.us>
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