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Re: Re: DBI perpare_cached and statment handle gone bad

by runrig (Abbot)
on Jul 08, 2003 at 23:36 UTC ( #272514=note: print w/replies, xml ) Need Help??


in reply to Re: DBI perpare_cached and statment handle gone bad
in thread DBI perpare_cached and statment handle gone bad

my $sth = $dbh->prepare_cached($statement) || try_again();
That won't do what you think it does. The error is occuring on the execute, not the prepare. And prepare_cached will just return the previously prepared statement handle (which, assuming the database changed, will now be an invalid handle, but a handle nonetheless), and your try_again() will not be called.

What the OP might want to do, if caching the statement handle is worth the trouble, is cache the handle himself without using prepare_cached, and re-prepare it if it fails on the execute.

Or use prepare_cached, and if the execute fails, look at the hash ref returned by the CachedKids dbh attribute, delete the statement handle from that, and re-prepare.

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Re: Re: Re: DBI perpare_cached and statment handle gone bad
by leriksen (Curate) on Jul 09, 2003 at 02:15 UTC
    Actually one could use eval to emulate a try-catch scenario (wuch is really one of the main uses of eval)
    eval { # try $sth->execute(); #throw }; if ($@) { #catch if (<error text indicates a recoverable statement handle error) { ...delete cached statement handle, re-prepare SQL and re-execute... } }
      What I'm doing is a step beyond that. I'm using Error (which implements a try-catch type system) and have the following code:
      my $dbh = try { DBI->connect( $conn_string, $props{USER}, $props{PWD}, { PrintError => 0, RaiseError => 1, }, ) } otherwise { throw Error::Database -text => ( $DBI::errstr || $@ || "Unknown Error: '$conn_string'" ); }; $dbh->{HandleError} = sub { throw Error::Database -text => $DBI::er +rstr }; return $dbh;
      I've defined Error::Database as such:
      package Error::Database; ###################################################################### +########## use 5.6.0; use strict; use warnings; ###################################################################### +########## # This is a baseclass I use for extending the standard Error class in +ways that don't matter here. use Error::Base; our @ISA = qw(Error::Base); ###################################################################### +########## sub new { my $class = shift; my $self = $class->SUPER::new(@_) || return undef; my $txt = $self->text; if ($txt =~ /text=([^=]+)./) { $self->{-text} = $1; } elsif ($txt =~ /Message String: (.*?)$/) { $self->{-text} = $1; } return $self; } 1;
      The reason for the regexes is I wanted to strip off meaningless guck to me and only giv eme the good stuff.

      ------
      We are the carpenters and bricklayers of the Information Age.

      Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.

      Please remember that I'm crufty and crochety. All opinions are purely mine and all code is untested, unless otherwise specified.

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