2011/2/10 Tobias Brox <tobixen@xxxxxxxxx>
On 4 February 2011 04:46, Josh Berkus <josh@xxxxxxxxxxxx> wrote:I have no clue about how hints works in Oracle ... I've never been
> "Optimizer hints are used to work around problems in the optimizer and
> introduce upgrade and maintenance issues. We would rather have the
> problems reported and fixed. We have discussed a more sophisticated
> system of per-class cost adjustment instead, but a specification remains
> to be developed."
working "enterprise level" on anything else than Postgres. Anyway,
today I just came over an interesting problem in our production
database today - and I think it would be a benefit to be able to
explicitly tell the planner what index to use (the dev team is adding
redundant attributes and more indexes to solve the problem - which
worries me, because we will run into serious problems as soon as there
won't be enough memory for all the frequently-used indexes).
We have users and transactions, and we have transaction types. The
transaction table is huge. The users are able to interactively check
their transaction listings online, and they have some simple filter
options available as well. Slightly simplified, the queries done
looks like this:
select * from account_transaction where account_id=? order by
created desc limit 25;
select * from account_transaction where trans_type_id in ( ...
long, hard-coded list ...) and account_id=? order by created desc
limit 25;
and we have indexes on:
account_transaction(account_id, created)
account_transaction(account_id, trans_type_id, created)
If the list is hard-coded, you can create partial index on account_transaction(account_id, created desc) where trans_type_id in ( ...
long, hard-coded list ...) --
Best regards,
Vitalii Tymchyshyn
