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Re: Better diagnostic support in DBI

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From:
pali
Date:
January 29, 2019 12:16
Subject:
Re: Better diagnostic support in DBI
Message ID:
20190129121623.5byuv6afzormj4cc@pali
CCing DBD::Pg, DBD::Oracle and DBD::ODBC developers. What do you think
about following diagnostic API in DBI?

I looked at DBD::Pg and currently it does not support retrieving
warnings via $dbh->errstr or $dbh->state methods... So I think it that
my diagnostic API proposal can be useful for DBD::Pg too.

On Wednesday 23 January 2019 11:15:35 pali@cpan.org wrote:
> Hi! DBI currently supports 3 functions to retrieve diagnostic
> informations
> 
> https://metacpan.org/pod/DBI#err
> https://metacpan.org/pod/DBI#errstr
> https://metacpan.org/pod/DBI#state
> 
> which return the last one database native code, message and SQLSTATE.
> Plus there warning or note information is indicated by zero native code
> or by empty string in native code.
> 
> This API has two big limitations:
> 
> 1) It does not support providing database native code for warnings and
>    note informations.
> 
> 2) It does not support providing more warnings, errors or note
>    informations.
> 
> It most cases database native code is what application can "parse" and
> decide how to handle it. So absence of database native code for warnings
> or note informations can be a problem -- as currently DBI application
> needs to parse string message from $dbh->errstr.
> 
> Also databases can return more warnings or note informations for the
> last executed call. For this case DBI defines API for errstr just as:
> 
> "The returned string may contain multiple messages separated by newline
> characters."
> 
> So it is harder for DBI application to parse multi warnings. And there
> is not information for which warning is value from $dbh->state.
> 
> 
> 
> Based on above two limitations I would like to propose a new API for
> diagnostic messages (errors, warnings and note / success with
> information).
> 
> New method call "get_diagnostics()" for all DBI handles. It would
> return array of diagnostics member. Each diagnostic member would contain
> reference to array with 4 members: type, native code, message, sqlstate.
> 
> Type can be non-zero for errors, zero for warnings and empty string for
> notes / success with information. Like what $dbh->err now returns.
> 
> Native code is native database code, same what $dbh->err returns for
> errors. But for warnings and notes it would also contain database native
> code, not just false value
> 
> Message and sqlstate would return $dbh->errstr and $dbh->state.
> 
> Example of usage:
> 
>   my @array = $dbh->get_diagnostics();
>   foreach (@array) {
>     my ($type, $code, $message, $sqlstate) = @{$_};
>     if ($type) {
>       print "Error $code ($sqlstate): $message\n";
>     } elsif ($type eq '0') {
>       print "Warning $code ($sqlstate): $message\n";
>     } else {
>       # Process success with information message
>     }
>   }
> 
> What do you think about it?

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