Changeset 564

Timestamp:

02/05/09 00:27:19 (10 months ago)

Author:

athomason

Message:

Avoid joining to the same table multiple times.

Files:

• trunk/lib/Data/ObjectDriver/SQL.pm (modified) (3 diffs)

trunk/lib/Data/ObjectDriver/SQL.pm

@@ -72 +72 @@
 
     ## Add any explicit JOIN statements before the non-joined tables.
+    my %joined;
+    my @from = @{ $stmt->from || [] };
     if ($stmt->joins && @{ $stmt->joins }) {
         my $initial_table_written = 0;
@@ -78 +80 @@
             $table = $stmt->_add_index_hint($table); ## index hint handling
             $sql .= $table unless $initial_table_written++;
+            $joined{$table}++;
             for my $join (@{ $j->{joins} }) {
                 $sql .= ' ' .
@@ -84 +87 @@
             }
         }
-        $sql .= ', ' if @{ $stmt->from };
-    }
-
-    if ($stmt->from && @{ $stmt->from }) {
-        $sql .= join ', ', map { $stmt->_add_index_hint($_) } @{ $stmt->from };
+        @from = grep { ! $joined{ $_ } } @from;
+        $sql .= ', ' if @from;
+    }
+
+    if (@from) {
+        $sql .= join ', ', map { $stmt->_add_index_hint($_) } @from;
     }