RE: libpq debug log

Hi Alvaro san, 

Thank you for your update :)

> Opinions?  I experimented by patching psql as below (not intended for
> commit) and it looks good.  Only ErrorResponse prints the terminator as a
> control character, or something:
I check code, changes and email. I agree with all of this. 
I will review code, feature and performance if it is needed more closely. 
(I'll start it next week.)

Regards,
Aya Iwata

> -----Original Message-----
> From: Alvaro Herrera <alvherre@2ndquadrant.com>
> Sent: Thursday, September 17, 2020 5:42 AM
> To: Iwata, Aya/岩田 彩 <iwata.aya@fujitsu.com>
> Cc: pgsql-hackers@postgresql.org; tgl@sss.pgh.pa.us;
> robertmhaas@gmail.com; pchampion@pivotal.io; jdoty@pivotal.io;
> raam.soft@gmail.com; Nagaura, Ryohei/永浦 良平
> <nagaura.ryohei@fujitsu.com>; nagata@sraoss.co.jp;
> peter.eisentraut@2ndquadrant.com; 'Kyotaro HORIGUCHI'
> <horiguchi.kyotaro@lab.ntt.co.jp>; Jamison, Kirk/ジャミソン カーク
> <k.jamison@fujitsu.com>
> Subject: Re: libpq debug log
> 
> Hello Aya Iwata,
> 
> I like this patch, and I think we should have it.  I have updated it, as it had
> conflicts.
> 
> In 0002, I remove use of ftime(), because that function is obsolete.
> However, with that change we lose printing of milliseconds in the trace lines.
> I think that's not great, but I also think we can live without them until
> somebody gets motivated to write the code for that.  It seems a little messy
> so I'd prefer to leave that for a subsequent commit.
> (Maybe we can just use pg_strftime.)
> 
> Looking at the message type tables, I decided to get rid of the "bf"
> table, which had only two bytes, and instead put CopyData and CopyDone in
> the other two tables.  That seems simpler.  Also, the COMMAND_x_MAX
> macros were a bit pointless; I just expanded at the only caller of each, using
> lengthof().  And since the message type is unsigned, there's no need to do "c
> >= 0" since it must always be true.
> 
> I added setlinebuf() to the debug file.  Works better than without, because
> "tail -f /tmp/libpqtrace.log" works as you'd expect.
> 
> One thing that it might be good to do is to avoid creating the message type
> tables as const but instead initialize them if and only if tracing is enabled, on
> the first call.  I think that would not only save space in the constant area of
> the library for the 99.99% of the cases where tracing isn't used, but also make
> the initialization code be more sensible (since presumably you wouldn't have
> to initialize all the
> zeroes.)
> 
> Opinions?  I experimented by patching psql as below (not intended for
> commit) and it looks good.  Only ErrorResponse prints the terminator as a
> control character, or something:
> 
> 2020-09-16 13:27:29.072 -03  < ErrorResponse 117 S "ERROR" V "ERROR" C
> "42704" M "no existe el slot de replicación «foobar»" F "slot.c" L "408" R
> "ReplicationSlotAcquireInternal" ^@
> 
> 
> diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c index
> 8232a0143b..01728ba8e8 100644
> --- a/src/bin/psql/startup.c
> +++ b/src/bin/psql/startup.c
> @@ -301,6 +301,11 @@ main(int argc, char *argv[])
> 
>      psql_setup_cancel_handler();
> 
> +    {
> +        FILE *trace = fopen("/tmp/libpqtrace.log", "a+");
> +        PQtrace(pset.db, trace);
> +    }
> +
>      PQsetNoticeProcessor(pset.db, NoticeProcessor, NULL);
> 
>      SyncVariables();
> 
> --
> Álvaro Herrera                https://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services