Re: Modify the DECLARE CURSOR command tag depending on the scrollable flag

Boszormenyi Zoltan <zb@cybertec.at> writes:
> If you consider all these:

> - certain combinations of query and DECLARE stmt flags fail;
> - adding NO SCROLL is breaking backward compatibility;
> - the readahead code has to really know whether the cursor is
>    scrollable so it can behave just like the server;

If you're claiming that readahead inside ECPG will behave absolutely
transparently in all cases, I think that's bogus anyway.  Consider for
example a query that will get a divide-by-zero error when it computes
the 110th row --- but the application stops after fetching 100 rows.
Everything's fine, until you insert some readahead logic.  Queries
containing volatile functions might also not be happy about readahead.

Given these considerations, I think it'd be better to allow explicit
application control over whether read-ahead happens for a particular
query.  And I have no problem whatsoever with requiring that the cursor
be explicitly marked SCROLL or NO SCROLL before read-ahead will occur.
        regards, tom lane