PostgreSQL: Add a view "dual" to make some SQL statements portable.

src/lib/Sympa/DatabaseDriver/PostgreSQL.pm

@@ -61,11 +61,19 @@ sub connect {
 
     # - Configure Postgres to use ISO format dates.
     # - Set client encoding to UTF8.
+    # - Create a temporary view "dual" for portable SQL statements.
     # Note: utf8 flagging must be disabled so that we will consistently use
-    # UTF-8 bytestring as internal format.
+    #   UTF-8 bytestring as internal format.
+    # Note: PostgreSQL <= 8.0.x didn't support temporary view but >= 7.3.x
+    #   supported CREATE OR REPLACE statement.
     $self->__dbh->{pg_enable_utf8} = 0;    # For DBD::Pg 3.x
     $self->__dbh->do("SET DATESTYLE TO 'ISO';");
     $self->__dbh->do("SET NAMES 'utf8'");
+    defined $self->__dbh->do(
+        q{CREATE TEMPORARY VIEW dual AS SELECT 'X'::varchar(1) AS dummy;}
+    ) or $self->__dbh->do(
+        q{CREATE OR REPLACE VIEW dual AS SELECT 'X'::varchar(1) AS dummy;}
+    );
 
     return 1;
 }