Re: Query runs very slowly in Postgres, but very fast in other DBMS

Andrus Moor wrote:
> SELECT dokumnr FROM rid WHERE dokumnr NOT IN
> (select dokumnr FROM dok);
...
> Is it possible to speed up this query is Postgres ? How to force Postgres to 
> use indexes for this query ?

Use IN and NOT IN only for small sets. Use JOIN (instead of IN) and LEFT 
JOIN (instead of NOT IN) for larger sets. e.g.:

SELECT rid.dokumnr
FROM rid
LEFT JOIN dok ON (dok.dokumnr = rid.dokumnr)
WHERE dok.dokumnr iS NULL;

Cheers,

Ezequiel Tolnay