On Thursday, December 13, 2012 8:02 PM Merlin Moncure wrote: > On Thu, Dec 13, 2012 at 7:06 AM, Hari Babu <haribabu.ko...@huawei.com> > wrote: > > Please find the review of the patch. > > > Thanks for detailed review! > > > Basic stuff: > > ------------ > > - Patch applies with offsets. > > - Compiles cleanly with no warnings > > - Regression Test pass. > > > > Code Review: > > ------------- > > 1. Better to set the hint bits for the tuples in a page, if > the page > > is already dirty. > > This is true today but likely less true if/when page checksums come > out. Also it complicates the code a little bit. > > > Default tables select : 64980.736149 64550.118693 > > Unlogged tables select: 64874.974334 64550.118693 > > So it looks like the extra tests visibility routines are causing 0.7% > performance hit. > > > Multiple transaction bulk inserts: Select performance (refer script -1 > & 2 > > which attached) > > sequential scan: 6.492680 6.382014 > > Index scan: 1.386851 1.36234 > > > > Single transaction bulk inserts: Select performance (refer script - 3 > & 4 > > which attached) > > sequential scan: 6.49319 6.3800147 > > Index scan: 1.384121 1.3615277 > > The performance hit is higher here. Almost 2%. This is troubling. > > > Long transaction open then Vacuum & select performance in milli > seconds. > > (refer reports output) > > Testcase - 3: > > Single Vacuum Perf : 128.302 ms 181.292 ms > > Single select perf : 214.107 ms 177.057 ms > > Total : 342.409 ms 358.349 ms > > > > I was not able to find the reason why in some of cases results are low > so > > please use the attached scripts to validate the same. > > I need to validate the vacuum results. It's possible that this is > solvable by tweaking xmin check inside vacuum. Assuming that's fixed, > the question stands: do the results justify the change? I'd argue > 'maybe'
We can try with change (assuming change is small) and see if the performance gain is good, then discuss whether it really justifies. I think the main reason for Vacuum performance hit is that in the test pages are getting dirty only due to setting of hint bit by Vacuum. >-- I'd like to see the bulk insert performance hit reduced if > possible. I think if we can improve performance for bulk-insert case, then this patch has much more value. With Regards, Amit Kapila. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
