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Interpolate binds into SQL on error - DBI subclassing

by jZed (Prior)
on Oct 11, 2005 at 18:51 UTC ( #499253=snippet: print w/replies, xml ) Need Help??
Description: Here's a minimal subclass of DBI that illustrates how to subclass and adds interpolated binds to errors (i.e. it replaces SQL placeholders with the bind values). This isn't necessarily how your DBMS "sees" the statement, but it does give you a cut-and-pasteable approximation.

update Added Corion's fix to support questions marks in the bind values.

package MyDBI;
use base qw(DBI);

package MyDBI::db;
use base qw(DBI::db);

package MyDBI::st;
use base qw(DBI::st);

sub execute {
    my($sth,@binds)=@_;
    my $rv = eval { $sth->SUPER::execute(@binds) };
    return $rv unless $@;
    my $errmsg = $sth->errstr;
    my $err    = $sth->err   ;
    my $stmt = $sth->{Statement};
    @binds = map {
        $sth->{Database}->quote($_) 
        unless DBI::looks_like_number($_);
        $_;
    } @binds;
    $stmt =~ s/\?/shift @binds/eg;
    return $sth->set_err(
         $err,
         sprintf "Execution Error: %s\nReconstructed SQL=\n<\n%s\n>\n"
               , $errmsg, $stmt
    );
}
1;
Replies are listed 'Best First'.
Re: Interpolate binds into SQL on error - DBI subclassing
by Corion (Pope) on Oct 11, 2005 at 19:13 UTC

    This snippet will fail if the interpolated values themselves contain question marks - I would go for an eval-replace in the inner loop:

    for my $b(@binds) { $b=$sth->{Database}->quote($b) unless DBI::looks_like_number($b); }; $stmt =~ s/\?/shift @binds/eg;
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[ambrus]: Corion: those are good rules.
[ambrus]: Discipulus: oh sure. the input data has different filenames every time I get them.
[ambrus]: the directory structure may be 1, 2, or 3 deep, it may have spaces in the filename or not, it has dates in various format, different keywords for the same meanings, and the dates and other keywords are assembled in various ways.
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