title: Strange behaviour in Postgresql
body: <p>I'm new to Postgresql and I'm trying to migrate my application from MySQL.<br>
  I have a table with the following structure:</p>
  
  <pre><code>                            Table "public.tbl_point"
            Column         |         Type          | Modifiers | Storage  | Description
   ------------------------+-----------------------+-----------+----------+-------------
    Tag_Id                 | integer               | not null  | plain    |
    Tag_Name               | character varying(30) | not null  | extended |
    Quality                | integer               | not null  | plain    |
    Execute                | integer               | not null  | plain    |
    Output_Index           | integer               | not null  | plain    |
    Last_Update            | abstime               |           | plain    |
  Indexes:
  "tbl_point_pkey" PRIMARY KEY, btree ("Tag_Id")
  Triggers:
  add_current_date_to_tbl_point BEFORE UPDATE ON tbl_point FOR EACH ROW EXECUTE PROCEDURE update_tbl_point()
  Has OIDs: no
  </code></pre>
  
  <p>when I run the query through a C program using libpq:</p>
  
  <pre><code>UPDATE tbl_point SET "Execute"=0 WHERE "Tag_Id"=0
  </code></pre>
  
  <p>I got the following output:</p>
  
  <pre><code>ERROR:  record "new" has no field "last_update"
  CONTEXT:  PL/pgSQL function "update_tbl_point" line 3 at assignment
  </code></pre>
  
  <p>I get exactly the same error when I try to change the value of "Execute" or any other column using pgAdminIII.</p>
  
  <p>Everything works fine if I change the column name from "Last_Update" to "last_update".</p>
  
  <p>I found the same problem with other tables I have in my database and the column always appears with abstime or timestamp columns.</p>