Re: Access to current database from C-language function

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
findthe 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
andI 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
mostbasic operation I would need. Are cursors and option too? Is there a limitation for the number of open cursors? One
callmight open 100 cursors or so. 

cheers,
Achim