Am 26.07.2011 um 00:40 schrieb Florian Pflug:
> On Jul25, 2011, at 22:31 , Achim Domma wrote:
>> Am 25.07.2011 um 14:48 schrieb Florian Pflug:
>>> A more low-level API is provided by {heap,index}_{beginscan,endscan},
>>> heap_{insert,update,delete} and index_insert. However, correct handling of
>>> transactions using this API isn't easy - for example, to update a row you'd
>>> first have to find the latest version of that row, then decide if you're
>>> allowed to update it, and finally create a new version.
>>
>> I see the problems with the second approach, but that's definitively what I
>> would like to do.
>
> You're in for a lot of work, then. I still suggest that you explain your
> ultimate goals before you embark on your endeavor - people might be able to
> point our easier ways to achieve those.
I have tables which store two integer IDs and a floating point rank. So the
table MyTable might have these columns:
EntityID -> int
PropertyID -> int
Rank -> float
My algorithm needs to retrieve EntityID-Rank-Pairs for some given PropertyIDs.
So I basically want to execute a "select EntityID, Rank from MyTable where
PropertyID=123 oder by Rank desc". But I need to execute multiple of those
statements and I don't want to load all the data into memory, but rather
iterate over the results step by step, stopping at certain thresholds.
My algorithm is somewhat nested and contains logic which I cannot express in
SQL, but retrieving those pairs is the most basic operation I would need. Are
cursors and option too? Is there a limitation for the number of open cursors?
One call might open 100 cursors or so.
cheers,
Achim
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