[PERFORM] LEFT JOIN ON vs. LEFT JOIN USING performance

[Diego de Lima]

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