title: array_accum in postgresql is giving error
body: <p>my query is :</p>
  
  <pre><code>select d.id,array_to_string(array_accum('name',',')) as name from (select * from temp1 a left join temp3 c on a.id=c.leftid left join temp2 b on b.id=c.rightid) d group by d.id;
  </code></pre>
  
  <p>But it gives me following error : </p>
  
  <pre><code>ERROR:  function array_accum(unknown, unknown) does not exist
  </code></pre>