X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FManual%2FTroubleshooting.pod;h=820359d7c325ea08f6d1133cee7b98375d44aebe;hb=48580715af3072905f2c71dc27e7f70f21a11338;hp=cf4d5b825d156f7fffcac8d779f5a37dc1d877dc;hpb=dc253b7737070a66859d615ec79522522a0b1e8e;p=dbsrgits%2FDBIx-Class.git

diff --git a/lib/DBIx/Class/Manual/Troubleshooting.pod b/lib/DBIx/Class/Manual/Troubleshooting.pod
index cf4d5b8..820359d 100644
--- a/lib/DBIx/Class/Manual/Troubleshooting.pod
+++ b/lib/DBIx/Class/Manual/Troubleshooting.pod
@@ -17,13 +17,13 @@ SQL tracing, so to see what is happening try
 
 Alternatively use the C<< storage->debug >> class method:-
 
-  $class->storage->debug(1);
+  $schema->storage->debug(1);
 
 To send the output somewhere else set debugfh:-
 
-  $class->storage->debugfh(IO::File->new('/tmp/trace.out', 'w');
+  $schema->storage->debugfh(IO::File->new('/tmp/trace.out', 'w');
 
-Alternatively you can do this with the environment variable too:-
+Alternatively you can do this with the environment variable, too:-
 
   export DBIC_TRACE="1=/tmp/trace.out"
 
@@ -47,13 +47,12 @@ correctly.
 
 L<DBI> version 1.50 and L<DBD::Pg> 1.43 are known to work.
 
-=head2 ... Can't locate object method "source_name" via package ...
+=head2 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, so for a schema C< MySchema > you need to
-specify a fully qualified namespace: C< package MySchema::MyTable; >
-for example.
+declaration is correct. For example, for a schema C< MySchema > 
+you need to specify a fully qualified namespace: C< package MySchema::MyTable; >.
 
 =head2 syntax error at or near "<something>" ...
 
@@ -100,35 +99,27 @@ The solution is to enable quoting - see
 L<DBIx::Class::Manual::Cookbook/Setting_quoting_for_the_generated_SQL> for
 details.
 
-Note that quoting may lead to problems with C<order_by> clauses, see
-L<... column "foo DESC" does not exist ...> for info on avoiding those.
-
 =head2 column "foo DESC" does not exist ...
 
-This can happen if you've turned on quoting and then done something like
-this:
+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' ] } );
 
-This results in SQL like this:
-
-  ... ORDER BY "name DESC"
-
-The solution is to pass your order_by items as scalar references to avoid
-quoting:
-
-  $rs->search( {}, { order_by => [ \'name DESC' ] } );
+Since L<DBIx::Class> >= 0.08100 and L<SQL::Abstract> >= 1.50 the above
+should be written as:
 
-Now you'll get SQL like this:
+  $rs->search( {}, { order_by => { -desc => 'name' } } );
 
-  ... ORDER BY name DESC
+For more ways to express order clauses refer to
+L<SQL::Abstract/ORDER_BY_CLAUSES>
 
 =head2 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 Linix).
+White Box and Scientific Linux).
 
 Distributions affected include Fedora 5 through to Fedora 8 and RHEL5
 upto and including RHEL5 Update 2. Fedora 9 (which uses perl 5.10) has
@@ -141,20 +132,31 @@ 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
 
-The issue is due to perl doing an exhaustive search of blessed objects
+This issue is due to perl doing an exhaustive search of blessed objects
 under certain circumstances.  The problem shows up as performance
-degredation exponential to the number of L<DBIx::Class> row objects in
-memory, so can be unoticeable with certain data sets, but with huge
+degradation exponential to the number of L<DBIx::Class> row objects in
+memory, so can be unnoticeable with certain data sets, but with huge
 performance impacts on other datasets.
 
-A pair of tests for susceptability to the issue, and performance effects
+A pair of tests for susceptibility to the issue and performance effects
 of the bless/overload problem can be found in the L<DBIx::Class> test
-suite in the file C<t/99rh_perl_perf_bug.t>
+suite, in the C<t/99rh_perl_perf_bug.t> file.
 
 Further information on this issue can be found in
 L<https://bugzilla.redhat.com/show_bug.cgi?id=379791>,
 L<https://bugzilla.redhat.com/show_bug.cgi?id=460308> and
 L<http://rhn.redhat.com/errata/RHBA-2008-0876.html>
 
+=head2 Excessive Memory Allocation with TEXT/BLOB/etc. Columns and Large LongReadLen
+
+It has been observed, using L<DBD::ODBC>, that creating a L<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 row 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.
+
 =cut