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

2015-09-02 21:49 GMT+02:00 dinesh kumar <dineshkumar02@gmail.com>:

On Mon, Aug 31, 2015 at 10:08 PM, Pavel Stehule <pavel.stehule@gmail.com> wrote:

2015-09-01 6:59 GMT+02:00 Pavel Stehule <pavel.stehule@gmail.com>:

2015-08-31 20:43 GMT+02:00 dinesh kumar <dineshkumar02@gmail.com>:

Hi,

On Sat, Aug 29, 2015 at 4:22 PM, Pavel Stehule <pavel.stehule@gmail.com> wrote:

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, ...

Added these functionalities too.

 

2. Missing regress tests

Adding here.

 

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

Sorry Pavel. I am not getting your point here. Would you give me an example.

The transformation: text -> error level is common task - and PLpgSQL it does in pl_gram.y. My idea is to add new function to error utils named "parse_error_level" and use it from PLpgSQL and from your code.

 

 

4. should be hidestmt mandatory parameter?

I changed this argument's default value as "true".
 

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

I took quote_ident(anyelement) as referral code, for implementing this. Could you guide me if I am doing wrong here.

I was wrong - this is ok - it is emulation of force casting to text

 

 

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.

Fixed these to 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

You mean, if the elevel is 'ERROR', then we need to allow errcode. Let me know your inputs.

I was blind, but the code was not good. Yes, error and higher needs error code. From ANSI/SQL anything can has error code "00 is ok", "01 .. warnings" ...

There is more possibilities - look to PLpgSQL implementation - it can be optional parameter - it default can use ERRCODE_RAISE_EXCEPTION
 

Adding new patch, with the above fixes.

the code looks better

my objections:

1. I prefer default values be NULL

Fixed it.
 

2. readability:

  * parsing error level should be in alone cycle

  * you don't need to use more ereport calls - one is good enough - look on implementation of stmt_raise in PLpgSQL

 

Sorry for my ignorance. I have tried to implement parse_error_level in pl_gram.y, but not able to do it. I was not able to parse the given string with tokens, and return the error levels. I tried for a refferal code, but not able to find any. Would you guide me on this.

you have a true - in this case we can use YYTEXT - so the code can be some like

if (tok != ';')
{

    if (parse_elog_level(yytext, &elog_level)
    {
       ...
    }

}

but it means double string comparation, what is not good, or removing elog levels from keyword list (what is surely out of area of this patch). So using it in PLpgSQL was not practical  idea. I am sorry.

Regards

Pavel

In this attached patch, I have minimized the ereport calls. Kindly check and let me know.

 

3. test should be enhanced for optional parameters

Fixed it.

Regards,

Dinesh

manojadinesh.blogspot.com

Regards

Pavel

 

Thanks in advance.

Regards,
Dinesh

Regards

Pavel

 

Regards,
Dinesh
manojadinesh.blogspot.com