Fix comment detection

On psql 8.1, `pg_catalog.shobj_description` does not exist. Also, if the
database to comment is not the current db then this warning will be
raised and the comment will not be applied: `WARNING:  database comments
may only be applied to the current database`

This fix uses the pg_* databases to find the comment based on the
database oid rather than the shared object description function.

manifests/server/database.pp

@@ -78,10 +78,15 @@
   }
 
   if $comment {
+    # The shobj_description function was only introduced with 8.2
+    $comment_information_function =  $version ? {
+      '8.1'   => 'obj_description',
+      default => 'shobj_description',
+    }
     Exec[ $createdb_command ]->
     postgresql_psql {"COMMENT ON DATABASE ${dbname} IS '${comment}'":
-      unless  => "SELECT description FROM pg_description JOIN pg_database ON objoid = pg_database.oid WHERE datname = '${dbname}' AND description = '${comment}'",
-      db      => $dbname,
+      unless => "SELECT pg_catalog.${comment_information_function}(d.oid, 'pg_database') as \"Description\" FROM pg_catalog.pg_database d WHERE datname = '${dbname}' AND pg_catalog.${comment_information_function}(d.oid, 'pg_database') = '${comment}'",
+      db     => $dbname,
     }
   }
 

spec/acceptance/db_spec.rb

@@ -29,7 +29,14 @@ class { 'postgresql::server': }
         expect(r.stdout).to match(/\(1 row\)/)
       end
 
-      psql('--command="SELECT pg_catalog.shobj_description(d.oid, \'pg_database\') FROM pg_catalog.pg_database d WHERE datname = \'postgresql_test_db\' AND pg_catalog.shobj_description(d.oid, \'pg_database\') = \'testcomment\'"') do |r|
+      result = shell('psql --version')
+      version = result.stdout.match(%r{\s(8\.\d)})[1]
+      if version > "8.1"
+        comment_information_function = "shobj_description"
+      else
+        comment_information_function = "obj_description"
+      end
+      psql("--dbname postgresql_test_db --command=\"SELECT pg_catalog.#{comment_information_function}(d.oid, 'pg_database') FROM pg_catalog.pg_database d WHERE datname = 'postgresql_test_db' AND pg_catalog.#{comment_information_function}(d.oid, 'pg_database') = 'testcomment'\"") do |r|
         expect(r.stdout).to match(/\(1 row\)/)
       end
     ensure