The semantics are good for us. The potential overhead from the implementation isn't a concern for our uses. What was the feedback from the MPAB code review?
On Fri, Jan 20, 2012 at 7:37 AM, MARK CALLAGHAN <mdcal...@gmail.com> wrote: > OK, will have feedback in a few days. > > On Fri, Jan 20, 2012 at 6:45 AM, Timour Katchaounov > <tim...@montyprogram.com> wrote: >> Hello Mark, >> >> >>> I want a variant of the LIMIT clause that limits the number of rows >>> examined during SELECT processing. This should return OK when the >>> limit is reached -- something like NESTED_LOOP_QUERY_LIMIT. While >>> LIMIT can be LIMIT x and LIMIT x,y. This only supports one argument -- >>> LIMIT_ROWS_EXAMINED x. Are you interested in implementing this feature >>> for me? We will sponsor the work. The purpose of the feature is to >>> prevent queries from taking too long when there isn't a great index >>> and many rows might be filtered. >>> >> >> After examining few alternatives, I implemented a pretty complete >> prototype of LIMIT_ROWS_EXAMINED. Please have a look at the description >> of the task here: >> https://mariadb.atlassian.net/browse/MDEV-28 >> >> It is important to notice that the current implementation will stop >> execution when LIMIT_ROWS_EXAMINED is reached irrespective of the >> query execution strategies used (thus not only for JOINs, but also >> writing/reading to temp tables, sorting, and single-table access methods >> that scan too many rows). This approach also is future-proof with >> respect to adding new query processing algorithms because the counting >> is done at the handler level. >> >> The current approach is such, that it should be fairly easy to backport >> the feature to almost any MariaDB/MySQL. >> >> Please let me know if this is what you want. If so, then I will proceed >> with the remaining polishing that is in the TODO list and will get an >> internal review. >> >> You can also have a look at the small example in the comments below the >> description to get a feeling what is the behavior. >> >> I can also send you a patch of the current version in case you want to >> play with the feature before it is pushed. >> >> Timour > > > > -- > Mark Callaghan > mdcal...@gmail.com -- Mark Callaghan mdcal...@gmail.com _______________________________________________ Mailing list: https://launchpad.net/~maria-developers Post to : maria-developers@lists.launchpad.net Unsubscribe : https://launchpad.net/~maria-developers More help : https://help.launchpad.net/ListHelp
