On Thu, Apr 13, 2006 at 08:32:34AM -0400, Stephen Frost wrote: > * Martijn van Oosterhout (kleptog@svana.org) wrote: > > Hmm, the simplest improvement I can think of is one where you > > register a callback that libpq calls whenever it has received a new > > tuple. > > You wouldn't want it on every tuple as that'd get expensive through > function calls.
Why not? Internally we call pqAddTuple for every tuple, calling a user function instead is hardly going to be more expensive. Also, I was thinking of the situation where the user function could set a flag so the eventual caller of (perhaps) PQconsumeInput knows that it's got enough for now. > It's actually pretty common (or seems to be anyway) to want to store the > data from the query result into your own data structure. Yes, you could > just use pointers all over the place but that means you're going to have > to use things which understand PQresult everywhere as opposed to having a > generic 'storage manager' with other generic things (index creator, > aggregator, etc) which can be used with more than just PQresults. <snip> > You don't provide a callback, you have the user provide a memory region > to libpq which libpq can then fill in. It's really not that difficult, > the API would really look quite a bit like PQexecParams, ie: Except in the case of psqlODBC, it wants to be able to malloc/free() each field, which your method doesn't solve. Also, it doesn't solve the duplicate memory use, nor the retreiving of rows before the resultset is complete. > If we want to do conversion of the data in some way then we may need to > expand this to include that ability (but I don't think PQgetvalue does, > so...). I think a callback is much easier. As a bonus the user could specify that libpq doesn't need to remember the rows. Memory savings. Have a nice day, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a > tool for doing 5% of the work and then sitting around waiting for someone > else to do the other 95% so you can sue them.
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