On Friday, April 5, 2013 11:58:37 PM UTC+2, Martin Barnard wrote:
>
> Thanks for the info, Niphlod.
>
> I will look into the efficiency of the IN clause for my needs, as it
> appears to offer a solution which may mollify the IT DBA, and his demands
> for bind vars (they are concerned that a looped select will bring the db to
> it's knees).
>
>
.... a db(whatever.belongs(a_set)) issues ONE query only.
If you want to "force" a looping query, you should do explicitely with
mems = [1,2,3,4,5,6,...]
for c in mems:
one_result = db(db.table.field == c).select()
......
of course, for zillions values into mems, it's not a smart move.
the smartest move with a huge set (i.e. the technique with most of the
"balance") would be "paginating" through your "mems" .
You'd loop a few times but if you have thousands of values into "mems", a
single IN () (or thousands ORs) will take some time ....
Try to "draw a limit" with your DBA and if he says that you're "allowed" to
do an IN() with 500 values at a times, you have it covered ^_^
On the other end, you have a requirement..... fetch a zillions rows.....
either you do it in one shot or in zillions/500 each.
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