On 03/05/2011, at 4:20 AM, Ian MacLeod wrote:
DataMapper appears to be generating grossly sub-optimal queries
There's very little wrong with those queries, but there is a lot wrong with the MySQL optimiser. It's a heuristic optimiser, and every other RDBMS discarded that approach around 1985. Please consider using an RDBMS with a proper optimiser. Postgres is a good free option.
What can I do to improve the performance of these queries?
You should index all foreign keys. That should get rid of the temporary and sort in the query plan.
For one, the "INNER JOIN lefts ON joins.left_id = lefts.id" is completely unnecessary.
No, it isn't. You've asked DataMapper for the first Left, and all its Rights, and that's exactly what it's giving you. It has no way to know that you aren't using the Left it loads for you. Clifford Heath. -- You received this message because you are subscribed to the Google Groups "DataMapper" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/datamapper?hl=en.
