Re: psql's \watch is broken

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
Cc: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: psql's \watch is broken
Date: 2019-12-14 02:44:53
Message-ID: 20191214024453.GA3004@paquier.xyz
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On Sat, Dec 14, 2019 at 12:09:51AM +0100, Fabien COELHO wrote:
>
>> explain (analyze) select * from pgbench_accounts \watch 1
>>
>> It behaves as expected. But once I break out of the loop with ctrl-C, then
>> if I execute the same thing again it executes the command once, but shows
>> no output and doesn't loop. It seems like some flag is getting set with
>> ctrl-C, but then never gets reset.
>>
>>
>> I've not dug into code itself, I just bisected it.
>
> Thanks for the report. I'll look into it.

Looked at it already. And yes, I can see the difference. This comes
from the switch from cancel_pressed to CancelRequested in psql,
especially PSQLexecWatch() in this case. And actually, now that I
look at it, I think that we should simply get rid of cancel_pressed in
psql completely and replace it with CancelRequested. This also
removes the need of having cancel_pressed defined in print.c, which
was not really wanted originally. Attached is a patch which addresses
the issue for me, and cleans up the code while on it. Fabien, Jeff,
can you confirm please?
--
Michael

Attachment Content-Type Size
psql-cancel-fix.patch text/x-diff 16.3 KB

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