On Wed, Jan 25, 2012 at 4:07 PM, Richard Hipp <d...@sqlite.org> wrote:
> On Wed, Jan 25, 2012 at 4:01 PM, John Elrick <john.elr...@fenestra.com > >wrote: > > > Much better. I wasn't sure which version to incorporate the changes into > > (the link is to the source), so I put them into 3.7.9. > > > > The total mallocs have dropped to 1.5 million -- twice as high as 3.7.5 > but > > in line. I'll have to run some additional performance testing but > visually > > the system appears to be a lot closer to expected. > > > > What was going on? (My client will want a report on the resolution). > > > > The SQLite byte-code engine was being too conservative and was reparsing > the schema in places where it was not strictly necessary. The fix was to > restrict the places where the schema was reparsed to situations that really > needed it. > > I cannot give more detail without seeing your application, since I still > don't know exactly what you are doing to trigger the excess reparsing. The > patch above comes from a script of my own that I finally managed to put > together that caused unnecessary schema reparsing. It took a specific > combination of events: A schema change inside of a transaction followed by > DML statements that had been prepared prior to the schema change. > > My brain missed that. The sequence I described should have been: prepare query1 prepare query2 begin transaction create something -> schema change query1.step - schema invalid so recreate - recreation of schema changes the generation query2.step - schema invalid so recreate - recreation of schema changes the generation query1.step - schema invalid so recreate - recreation of schema changes the generation query2.step - schema invalid so recreate - recreation of schema changes the generation end transaction ...which I believe describes your scenario perfectly. Odd that the script didn't replicate it, since it should have had the nested transactions as well. Thank you very much for your assistance Richard. I sincerely appreciate it. Thanks to everyone else who helped guide me on this investigation. John _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
