On Dec 16, 2007 12:21 AM, <[EMAIL PROTECTED]> wrote: > Loïc Marteau <[EMAIL PROTECTED]> wrote .. > > Steve Crawford wrote: > > > If this > > > is correct, I'd first investigate simply loading the csv data into a > > > temporary table, creating appropriate indexes, and running a single > > > query to update your other table. > > My experience is that this is MUCH faster. My predecessor in my current > position was doing an update from a csv file line by line with perl. That is > one reason he is my predecessor. Performance did not justify continuing his > contract. > > > i can try this. The problem is that i have to make an insert if the > > update don't have affect a rows (the rows don't exist yet). The number > > of rows affected by insert is minor regards to the numbers of updated > > rows and was 0 when i test my script). I can do with a temporary table > > : update all the possible rows and then insert the rows that are in > > temporary table and not in the production table with a 'not in' > > statement. is this a correct way ? > > That's what I did at first, but later I found better performance with a > TRIGGER on the permanent table that deletes the target of an UPDATE, if any, > before the UPDATE. That's what PG does anyway, and now I can do the entire > UPDATE in one command.
that's very clever, and probably is the fastest/best way to do it. you can even temporarily add the trigger a transaction...I am going to try this out in a couple of things (I currently do these type of things in two statements) and see how it turns out. merlin ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
