Hi, Alexander! On Nov 03, Alexander Barkov wrote: > Hello Sergei, > > Please review a patch for MDEV-13790. > > It removes the attempt to search the best suitable buffer > and just returns the result in "str" passed to val_str(). > > I'm quite sure this optimization gives nothing. > In can be useful only under very rare conditions, > but generates so many bugs.
There're bunch of tricks. What do they all do, could you list them? One handles the case when an argument is a substring of the already concatenated string - this is very weird and rare, I agree. Other accumulates the result in the first argument's result - this avoids one memcpy per row. Doesn't sound like much, but it's not rare, so should be very easy to benchmark. Yet another doubles the buffer size every time - this might be useful to keep, it easily fits in your new code. What are other tricks that concat was using? Btw, one comment about your patch — please don't call current_thd in a loop. Regards, Sergei Chief Architect MariaDB and [email protected] _______________________________________________ Mailing list: https://launchpad.net/~maria-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~maria-developers More help : https://help.launchpad.net/ListHelp
