Re: Help with tuning this query
От | Ken Egervari |
---|---|
Тема | Re: Help with tuning this query |
Дата | |
Msg-id | 002801c51f59$9c043900$6a01a8c0@KEN обсуждение исходный текст |
Ответ на | Help with tuning this query ("Ken Egervari" <ken@upfactor.com>) |
Список | pgsql-performance |
>> left join is for eager loading so that I don't have to run a seperate >> query >> to fetch the children for each shipment. This really does improve >> performance because otherwise you'll have to make N+1 queries to the >> database, and that's just too much overhead. > > are you saying that you are actually doing a > select s.*,ss.* ... > ? Yes, this is how the SQL should be written. When I manually converted the query, I forgot to include this detail. In hibernate, you don't need to specifiy the ss.* because you are dealing with objects, so you just say shipment. The ss.* is indicated in the "fetch" part of the Hibernate query. That was my mistake. > it might help the planner estimate better the number of cs rows > affected. whether this improves performance depends on whether > the best plans are sensitive to this. This sounds like a good idea since cs rows are quite large. shipment and shipment_status are the largest tables in the database and they will grow very large over time.
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