#python - Tue 20 Mar 2007 between 00:00 and 00:17

NY Lost Funds



deltabmDuff: types.FunctionType
mDuffahh; graci
haysroygbiv: the queries are so simple.. its like SELECT * FROM foo WHERE x='bar' AND y='baz';
roygbive.g. cross product joins, indexed or not, can really grind a system when you have 50 million rows ;)
deltabor type(lambda: None)
actionmDuff obviously didn't look hard enough before coming here; sorry 'bout that.
mDuffobviously didn't look hard enough before coming here; sorry 'bout that.
haysroygbiv: no joins.. its just a flat database
roygbivi don't know. check ulimit? make sure your not being choked by OS constraints
mDuffhays: what you're describing is certainly not consistent with my experience w/ postgres.
haysroygbiv: now x is indexed and y is indexed, but I don't bother to index (x,y)
I wonder if they run on the same port
hmm
koshyou would want to ask the postgres planner how it was going to do the query
that should tell you where the problems are
roygbivyep the PG query planner is nice
but maybe not of much help on a simple single table select
koshit would tell if your query was written in such a way as to cause postgres to do a sequential table scan
so you could find out about problems
roygbivkosh but he says he has fully indexed queries and it's still taking 2 seconds
koshhe has the fields indexed
that does not mean that the db is using those indexes
that is why you need to ask the query planner
haysi would hope so
koshdepending on how you word a query a db can decide it is more efficient to do a linear scan instead of using an index
that is why you would want to see the plan
roygbivwell you're right, there could be some value to using the query planner. give it a try hays. might learn something interesting there...
koshtrying to predict what the db will do is usually a bad idea
I have had times where I figured that it should use indexes when it did not
and there are ways to force it and the db turned out to be right, it did run slower using the indexes
so guessing is a bad move, just ask the db what it is doing
hayshttp://rafb.net/p/3umVsF21.html <-- does this tell you guys anything? (MySQL)
koshthat seems to say it is using an index scan and only checking 225 rows
roygbivhays, not much ;) as expected. it's only 225 rows?
koshat least that is my reading
haysthat query takes 9 seconds
sinkaosI have an array class member. I want to only strings or objects of a particular type in that array. How do I arrange the class to ensure this?
hays225 rows are the output, I believe, there are many many rows in the whole table
Jerubsinkaos: uh, you're not making any semse.
sinkaos: no one uses arrays in python.
sinkaosLists, whatever.

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NY Lost Funds