=== modified file 'includes/database/pgsql/install.inc'
--- includes/database/pgsql/install.inc	2010-06-15 16:12:06 +0000
+++ includes/database/pgsql/install.inc	2010-06-18 23:28:22 +0000
@@ -109,18 +109,33 @@ class DatabaseTasks_pgsql extends Databa
         );
       }
 
-      // Don't use {} around pg_proc table.
-      if (!db_query("SELECT COUNT(*) FROM pg_proc WHERE proname = 'concat'")->fetchField()) {
-        db_query('CREATE OR REPLACE FUNCTION "concat"(text, text) RETURNS text AS
-          \'SELECT $1 || $2;\'
-          LANGUAGE \'sql\''
-        );
-      }
-
       db_query('CREATE OR REPLACE FUNCTION "substring_index"(text, text, integer) RETURNS text AS
         \'SELECT array_to_string((string_to_array($1, $2)) [1:$3], $2);\'
         LANGUAGE \'sql\''
       );
+
+      // Using || to concatenate in Drupal is not recommeneded because there are
+      // database drivers for Drupal that do not support the syntax, however
+      // they do support CONCAT(item1, item2) which we can replicate in
+      // PostgreSQL. PostgreSQL requires the function to be defined for each
+      // different argument variation the function can handle.
+      db_query('CREATE OR REPLACE FUNCTION "concat"(anynonarray, anynonarray) RETURNS text AS
+        \'SELECT CAST($1 AS text) || CAST($2 AS text);\'
+        LANGUAGE \'sql\'
+      ');
+      db_query('CREATE OR REPLACE FUNCTION "concat"(text, anynonarray) RETURNS text AS
+        \'SELECT $1 || CAST($2 AS text);\'
+        LANGUAGE \'sql\'
+      ');
+      db_query('CREATE OR REPLACE FUNCTION "concat"(anynonarray, text) RETURNS text AS
+        \'SELECT CAST($1 AS text) || $2;\'
+        LANGUAGE \'sql\'
+      ');
+      db_query('CREATE OR REPLACE FUNCTION "concat"(text, text) RETURNS text AS
+        \'SELECT $1 || $2;\'
+        LANGUAGE \'sql\'
+      ');
+
       $this->pass(st('PostgreSQL has initialized itself.'));
     }
     catch (Exception $e) {