Date: Mon, 15 Mar 2021 20:18:59 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>,
	Alexey Bashtanov <bashtanov@imap.cc>,
	Franck Verrot <franck@verrot.fr>, pgsql-hackers@postgresql.org
Subject: Re: [PATCH]: Allow errors in parameter values to be reported during
 the BIND phase itself..
Message-ID: <20210316011859.GC29463@telsasoft.com>
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On Mon, Mar 15, 2021 at 08:30:18PM -0400, Tom Lane wrote:
> +               /* Pop the error callback */
> +               error_context_stack = error_context_stack->previous;
> +
>                 /*
>                  * Once all parameters have been received, prepare for printing them
>                  * in errors, if configured to do so.  (This is saved in the portal,
>                  * so that they'll appear when the query is executed later.)
>                  */
>                 if (log_parameter_max_length_on_error != 0)
>                         params->paramValuesStr =
>                                 BuildParamLogString(params,
...

I think it's somewhat confusing that there's two callbacks.
The first one applies only during typinput/typreceive.
I guess the 2nd one should say that they're printed "in *future errors".

> +# Check that errors are reported during BIND phase, too

Actually, the v13 log_parameter_max_length_on_error feature works during BIND
too, but only after typinput of *all* params.

For example, this shows params when failing in GetCachedPlan().

| python3.5 -c "import pg,time; db=pg.DB('dbname=postgres host=/var/run/postgresql port=5432 host=/tmp'); q = db.query(\"SET backtrace_functions=pg_strtoint16; SET log_parameter_max_length_on_error=-1;\"); db.prepare('p', 'SELECT a::smallint from (select \$1 a)a'); db.query_prepared('p',66666);"

So my own description of the patch evolved from "show errors during BIND" to
"show errors during typinput of text params".

Thanks,
-- 
Justin