ata with a
   <TT
CLASS="STRUCTNAME"
>PGconn</TT
> or <TT
CLASS="STRUCTNAME"
>PGresult</TT
>
   and ensure that that data is freed at an appropriate time.
  </P
><P
>   Each registered event handler is associated with two pieces of data,
   known to <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> only as opaque <TT
CLASS="LITERAL"
>void *</TT
>
   pointers.  There is a <I
CLASS="FIRSTTERM"
>passthrough</I
> pointer that is provided
   by the application when the event handler is registered with a
   <TT
CLASS="STR