DBIx::Class::Manual::Troubleshooting

(source, CPAN)

#NAME

DBIx::Class::Manual::Troubleshooting - Got a problem? Shoot it.

#"Can't locate storage blabla"

You're trying to make a query on a non-connected schema. Make sure you got the current resultset from $schema->resultset('Artist') on a schema object you got back from connect().

#Tracing SQL

The DBIC_TRACE environment variable controls SQL tracing, so to see what is happening try

export DBIC_TRACE=1

Alternatively use the storage->debug class method:-

$schema->storage->debug(1);

To send the output somewhere else set debugfh:-

$schema->storage->debugfh(IO::File->new('/tmp/trace.out', 'w'));

Alternatively you can do this with the environment variable, too:-

export DBIC_TRACE="1=/tmp/trace.out"

#Can't locate method result_source_instance

For some reason the table class in question didn't load fully, so the ResultSource object for it hasn't been created. Debug this class in isolation, then try loading the full schema again.

#Can't get last insert ID under Postgres with serial primary keys

Older DBI and DBD::Pg versions do not handle last_insert_id correctly, causing code that uses auto-incrementing primary key columns to fail with a message such as:

Can't get last insert id at /.../DBIx/Class/Row.pm line 95

In particular the RHEL 4 and FC3 Linux distributions both ship with combinations of DBI and DBD::Pg modules that do not work correctly.

DBI version 1.50 and DBD::Pg 1.43 are known to work.

#Can't locate object method "source_name" via package

There's likely a syntax error in the table class referred to elsewhere in this error message. In particular make sure that the package declaration is correct. For example, for a schema MySchema you need to specify a fully qualified namespace: package MySchema::MyTable; .

#syntax error at or near "<something>" ...

This can happen if you have a relation whose name is a word reserved by your database, e.g. "user":

package My::Schema::User;
...
__PACKAGE__->table('users');
__PACKAGE__->add_columns(qw/ id name /);
__PACKAGE__->set_primary_key('id');
...
1;

package My::Schema::ACL;
...
__PACKAGE__->table('acl');
__PACKAGE__->add_columns(qw/ user_id /);
__PACKAGE__->belongs_to( 'user' => 'My::Schema::User', 'user_id' );
...
1;

$schema->resultset('ACL')->search(
  {},
  {
    join => [qw/ user /],
    '+select' => [ 'user.name' ]
  }
);

The SQL generated would resemble something like:

SELECT me.user_id, user.name FROM acl me
JOIN users user ON me.user_id = user.id

If, as is likely, your database treats "user" as a reserved word, you'd end up with the following errors:

1) syntax error at or near "." - due to "user.name" in the SELECT clause

2) syntax error at or near "user" - due to "user" in the JOIN clause

The solution is to enable quoting - see "Setting quoting for the generated SQL" in DBIx::Class::Manual::Cookbook for details.

#column "foo DESC" does not exist ...

This can happen if you are still using the obsolete order hack, and also happen to turn on SQL-quoting.

$rs->search( {}, { order_by => [ 'name DESC' ] } );

The above should be written as:

$rs->search( {}, { order_by => { -desc => 'name' } } );

For more ways to express order clauses refer to "ORDER BY CLAUSES" in SQL::Abstract::Classic

#Perl Performance Issues on Red Hat Systems

There is a problem with slow performance of certain DBIx::Class operations using the system perl on some Fedora and Red Hat Enterprise Linux system (as well as their derivative distributions such as Centos, White Box and Scientific Linux).

Distributions affected include Fedora 5 through to Fedora 8 and RHEL5 up to and including RHEL5 Update 2. Fedora 9 (which uses perl 5.10) has never been affected - this is purely a perl 5.8.8 issue.

As of September 2008 the following packages are known to be fixed and so free of this performance issue (this means all Fedora and RHEL5 systems with full current updates will not be subject to this problem):-

Fedora 8     - perl-5.8.8-41.fc8
RHEL5        - perl-5.8.8-15.el5_2.1

This issue is due to perl doing an exhaustive search of blessed objects under certain circumstances. The problem shows up as performance degradation exponential to the number of DBIx::Class result objects in memory, so can be unnoticeable with certain data sets, but with huge performance impacts on other datasets.

A pair of tests for susceptibility to the issue and performance effects of the bless/overload problem can be found in the DBIx::Class test suite, in the t/99rh_perl_perf_bug.t file.

Further information on this issue can be found in https://bugzilla.redhat.com/show_bug.cgi?id=379791, https://bugzilla.redhat.com/show_bug.cgi?id=460308 and http://rhn.redhat.com/errata/RHBA-2008-0876.html

#Excessive Memory Allocation with TEXT/BLOB/etc. Columns and Large LongReadLen

It has been observed, using DBD::ODBC, that creating a DBIx::Class::Row object which includes a column of data type TEXT/BLOB/etc. will allocate LongReadLen bytes. This allocation does not leak, but if LongReadLen is large in size, and many such result objects are created, e.g. as the output of a ResultSet query, the memory footprint of the Perl interpreter can grow very large.

The solution is to use the smallest practical value for LongReadLen.

#FURTHER QUESTIONS?

Check the list of additional DBIC resources.

#COPYRIGHT AND LICENSE

This module is free software copyright by the DBIx::Class (DBIC) authors. You can redistribute it and/or modify it under the same terms as the DBIx::Class library.

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