Merge 'trunk' into 'multiple_version_upgrade'

[dbsrgits/DBIx-Class.git] / lib / DBIx / Class / Manual / Troubleshooting.pod

diff --git a/lib/DBIx/Class/Manual/Troubleshooting.pod b/lib/DBIx/Class/Manual/Troubleshooting.pod
index e3b1ab3..5d46805 100644 (file)
--- a/lib/DBIx/Class/Manual/Troubleshooting.pod
+++ b/lib/DBIx/Class/Manual/Troubleshooting.pod
@@ -100,28 +100,20 @@ 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
 
@@ -156,5 +148,16 @@ 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 a 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