Re: [PATCH] SQL function to report log message - Mailing list pgsql-hackers

Hi

I am starting to work review of this patch

2015-07-13 9:54 GMT+02:00 dinesh kumar <dineshkumar02@gmail.com>:

Hi All,

Greetings for the day.

Would like to discuss on below feature here.

Feature:
    Having an SQL function, to write messages to log destination.

Justification:
    As of now, we don't have an SQL function to write custom/application messages to log destination. We have "RAISE" clause which is controlled by
log_ parameters. If we have an SQL function which works irrespective of log settings, that would be a good for many log parsers. What i mean is, in DBA point of view, if we route all our native OS stats to log files in a proper format, then we can have our log reporting tools to give most effective reports. Also, Applications can log their own messages to postgres log files, which can be monitored by DBAs too.

Implementation:
    Implemented a new function "pg_report_log" which takes one argument as text, and returns void. I took, "LOG" prefix for all the reporting messages.I wasn't sure to go with new prefix for this, since these are normal LOG messages. Let me know, if i am wrong here.

Here is the attached patch.

This patch is not complex, but the implementation doesn't cover a "ereport" well.

Although this functionality should be replaced by custom function in any PL (now or near future), I am not against to have this function in core. There are lot of companies with strong resistance against stored procedures - and sometimes this functionality can help with SQL debugging.

Issues:

1. Support only MESSAGE field in exception - I am expecting to support all fields: HINT, DETAIL, ...

2. Missing regress tests

3. the parsing ereport level should be public function shared with PLpgSQL and other PL

4. should be hidestmt mandatory parameter?

5. the function declaration is strange

postgres=# \sf pg_report_log (text, anyelement, boolean)
CREATE OR REPLACE FUNCTION pg_catalog.pg_report_log(text, anyelement, boolean)
 RETURNS void
 LANGUAGE sql
 STABLE STRICT COST 1
AS $function$SELECT pg_report_log($1::pg_catalog.text, $2::pg_catalog.text, $3::boolean)$function$

Why polymorphic? It is useless on any modern release

postgres=# \sf pg_report_log (text, text, boolean)
CREATE OR REPLACE FUNCTION pg_catalog.pg_report_log(text, text, boolean)
 RETURNS void
 LANGUAGE internal
 IMMUTABLE STRICT
AS $function$pg_report_log$function$

Why stable, why immutable? This function should be volatile.

6. using elog level enum as errcode is wrong idea - errcodes are defined in table http://www.postgresql.org/docs/9.4/static/errcodes-appendix.html

Regards

Pavel

 

Regards,
Dinesh
manojadinesh.blogspot.com