Re: Non-trivial rewriting sql query

I believe (while I'm not an expert on this) that rewrite system cannot
cope with dynamically-rewritten queries. (i.e. the rewrite rules where a
function must be called to obtain the result of rewrite rule).

A better possibility for you is to return a refcursor, and use on client
side "FETCH ALL from rc", if possible.

I.E, client would do:
select setup_query('c=0', 'rc');
fetch all from rc;

create function setup_query(text, refcursor) returns int4 as '
declare
qry alias for $1;
cur alias for $2;
begin
execute ''declare '' || cur || '' cursor for select ... '' || qry ||
ourfunc(....)




-alex
On Wed, 27 Jun 2001, Oleg Bartunov wrote:

> Jan,
> 
> we're thinking about possibility to integrate our full-text search
> into postgres. There are several problems we should thinking about
> but for now we have a question about rewrite system.
> 
> Is't possible to rewrite SQL query and execute it. Currently we build
> sql query outside of postgres using perl.
> 
> Let's consider some simple example:
> 
> create table tst ( a int4, b int4, c int4);
> 
>     select * from tst where a=2 and c=0;
> 
> we need something like:
> 
>     select * from tst where str and c=0;
> 
> where str is a string resulting by call ourfunc(table.a, 2)
> and looks like  'b=2*2 or b=(2-1)'
> 
> i.e. instead of original select we need to execute rewritten select
> 
>     select * from tst where (b=2*2 or b=(2-1)) and c=0;
> 
> in other words we need to know is't possible to recognise
> (operator, field,table) and rewrite part of sql by
> result of calling of ourfunc().
> 
> We're not sure if it's a question of rewrite system though.
> 
> Any pointers where to go would be very nice.
> 
>     Regards,
> 
>         Oleg
> 
> 
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