The information I require is the number of rows that will come from a SELECT which places a certain range restriction on an unindexed attribute...and I need this to not take much time relative to actually executing the query (constant time would be best).
eric. On Sat, Oct 20, 2001 at 03:06:58PM +0300, Sinisa Milivojevic wrote: > Eric writes: > > Well, answering my own email, what I thought was a bug is not one at > > all. I was mistaken in thinking that MySQL paid any attention to the > > WHERE conditions when optimizing the join order beyond determining > > which keys are used for the join, correct? > > > > This is really terrible for queries like mine where the query could be > > sped up by orders of magnitude if the join optimizer would just > > determine which table in the join to scan and which to do the key > > lookup on based on a more intelligent estimation of the number of rows > > from each table. It would have to go beyond looking at what keys are > > used in the join (since each of the tables in my query can be looked > > up by the same key) and account for the WHERE conditions placed on the > > tables in the join. > > > > Is there sufficient metadata to estimate rows coming from a table > > based on conditions placed on the attributes of that table? Where is > > it? Has anyone ever thought of coding this? Can anyone give me a > > place to start? > > > > eric. > > > > > > -- > > _____ _ > > | ____|(_) http://ir.iit.edu/~ej > > | _| | | Page me via ICQ at > > | |___ | | http://wwp.mirabilis.com/19022931 > > |______/ | or by mailing [EMAIL PROTECTED] > > |__/ > > > > > What information do you precisely require ?? > > The answer also depends on the API you are using and a method of > retrieval. > > For example, you can know how many rows you get if you use _store_ > instead of _use_ method, but that method is not applicable in the case > of larger result sets. > > -- > Regards, > __ ___ ___ ____ __ > / |/ /_ __/ __/ __ \/ / Mr. Sinisa Milivojevic <[EMAIL PROTECTED]> > / /|_/ / // /\ \/ /_/ / /__ MySQL AB, FullTime Developer > /_/ /_/\_, /___/\___\_\___/ Larnaca, Cyprus > <___/ www.mysql.com > > > --------------------------------------------------------------------- > Before posting, please check: > http://www.mysql.com/manual.php (the manual) > http://lists.mysql.com/ (the list archive) > > To request this thread, e-mail [EMAIL PROTECTED] > To unsubscribe, e-mail <[EMAIL PROTECTED]> > -- _____ _ | ____|(_) http://ir.iit.edu/~ej | _| | | Page me via ICQ at | |___ | | http://wwp.mirabilis.com/19022931 |______/ | or by mailing [EMAIL PROTECTED] |__/ --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
