Horton

Re: proposal - psql - use pager for \watch command

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Pavel Stehule <pavel.stehule@gmail.com>, vignesh C <vignesh21@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2021-07-13T17:50:38Z
Lists: pgsql-hackers 
Thomas Munro <thomas.munro@gmail.com> writes:
> Pushed, after retesting on macOS (with the fixed pspg that has by now
> arrived in MacPorts), FreeBSD and Linux.  Thanks!

After playing with this along the way to fixing the sigwait issues,
I have a gripe/suggestion.  If I hit control-C while the thing
is waiting between queries, eg

regression=# select now() \watch
Tue Jul 13 13:44:44 2021 (every 2s)

              now              
-------------------------------
 2021-07-13 13:44:44.396565-04
(1 row)

Tue Jul 13 13:44:46 2021 (every 2s)

              now              
-------------------------------
 2021-07-13 13:44:46.396572-04
(1 row)

^Cregression=# 

then as you can see I get nothing but the "^C" echo before the next
psql prompt.  The problem with this is that now libreadline is
misinformed about the cursor position, messing up any editing I
might try to do on the next line of input.  So I think it would
be a good idea to have some explicit final output when the \watch
command terminates, along the line of

...
Tue Jul 13 13:44:46 2021 (every 2s)

              now              
-------------------------------
 2021-07-13 13:44:46.396572-04
(1 row)

^C\watch cancelled
regression=# 

This strikes me as a usability improvement even without the
readline-confusion angle.

			regards, tom lane

Commits

  1. Fix \watch's interaction with libedit on ^C.

  2. Add PSQL_WATCH_PAGER for psql's \watch command.

  3. psql: Show all query results by default

  4. Add a comment warning against use of pg_usleep() for long sleeps.