LEFT JOIN ON vs. LEFT JOIN USING performance
| От | Diego de Lima |
|---|---|
| Тема | LEFT JOIN ON vs. LEFT JOIN USING performance |
| Дата | |
| Msg-id | 002a01c5a4d1$d36f6420$3dc8a8c0@diretoria02 обсуждение исходный текст |
| Ответы |
Re: LEFT JOIN ON vs. LEFT JOIN USING performance
Re: LEFT JOIN ON vs. LEFT JOIN USING performance |
| Список | pgsql-performance |
Hi list,
I´m using Pg 8.0.3 on Linux FC2.
This question may have a very simple answer (I hope), but I´m having lots of trouble solving it, and I counldn´t find any other post about it or anything in the pg docs.
I have some very complex select statements on 4 million rows tables. When using LEFT JOIN ON, some select statements takes about 2 minutes. When I write exactly the same statement but with LEFT JOIN USING, it takes only 1 minute. Comparing to Oracle, the same statement takes 1 minute also, but with LEFT JOIN ON.
Sometimes tables have the same column names and I can use LEFT JOIN USING, but in some other cases I MUST use LEFT JOIN ON, because the tables have different column names.
So my question is: is there a way to make LEFT JOIN ON uses the same plan of LEFT JOIN USING?
Thanks,
Diego de Lima
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