Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.lang.java.programmer > #32988
| From | Martin Gregorie <martin@address-in-sig.invalid> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: Performance JPA |
| Date | 2015-11-03 19:15 +0000 |
| Organization | A noiseless patient Spider |
| Message-ID | <n1b13k$rd7$1@dont-email.me> (permalink) |
| References | <87lhagkcsh.fsf@Equus.decebal.nl> <563763d9$0$23727$e4fe514c@news.xs4all.nl> <87d1vrk20x.fsf@Equus.decebal.nl> <n1a51v$4qh$1@dont-email.me> <87ziyvhs0r.fsf@Equus.decebal.nl> |
On Tue, 03 Nov 2015 19:11:48 +0100, Cecil Westerhof wrote: >> Bad performance can also be the result of poor DB management: most DBMS >> use DB statistics (row counts, etc) as input to the query optimiser. If >> these stats aren't automatically updated by the DBMS and the DBA >> doesn't update them regularly, or turned auto-stats update off then the >> optimiser can do a spectacularly poor job, e.g. if stats say a 100,000 >> table has only 10 rows then most optimisers would scan it sequentially >> because a sequential scan on a table that fits in one disk block will >> always be quicker than indexed access. > > But that should go wrong with JDBC and JPA I would think. > True, but are you running JPA against the original database instance that JDBC used to use, or has the data been copied into a clean development instance? I would hope the latter is the case because performance comparisons are invalid unless the data volumes are the same for both old and new code but it would be quite unwise to be running code under system test against the main database. If the data has been copied, then you need to be sure that the DB stats on the DB copy are up to date, which is what I was on about. You also need to be certain that the schemas are identical: it only needs tweaks to have been applied to the old database during a late night emergency fix, i.e. indices added to tables or the physical placement and/ or partitioning of database components changed, and for the fixer to forget to or not be given time to record the changes in the development schema and documentation for this sort of error to creep into the system. The worst part is that nobody will know this happened until the organisation needs to build a new integration test system after a major upgrade because its only then, when a clean instance has been set up and loaded with data from the old system that unexpected performance differences or outputs show up. Finding and fixing this sort of change can be a real headache. -- martin@ | Martin Gregorie gregorie. | Essex, UK org |
Back to comp.lang.java.programmer | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-02 09:47 +0100
Re: Performance JPA Silvio <silvio@internet.com> - 2015-11-02 14:23 +0100
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-03 07:52 +0100
Re: Performance JPA Martin Gregorie <martin@address-in-sig.invalid> - 2015-11-03 11:16 +0000
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-03 19:11 +0100
Re: Performance JPA Martin Gregorie <martin@address-in-sig.invalid> - 2015-11-03 19:15 +0000
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-04 09:28 +0100
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-10 08:07 +0100
Re: Performance JPA Silvio <silvio@internet.com> - 2015-11-10 10:35 +0100
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-11 06:20 +0100
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-11 09:32 -0500
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-10 19:56 -0500
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-11 06:50 +0100
Re: Performance JPA Martin Gregorie <martin@address-in-sig.invalid> - 2015-11-11 12:17 +0000
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-11 09:30 -0500
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-11 23:20 +0100
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-11 23:11 +0100
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-11 19:10 -0500
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-12 07:27 +0100
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-13 08:30 +0100
Re: Performance JPA Silvio <silvio@internet.com> - 2015-11-13 10:45 +0100
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-13 11:06 +0100
Re: Performance JPA Silvio <silvio@internet.com> - 2015-11-13 13:36 +0100
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-20 09:04 +0100
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-13 21:46 -0500
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-20 09:09 +0100
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-03 20:35 -0500
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-04 09:35 +0100
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-07 22:09 -0500
Re: Performance JPA Silvio <silvio@internet.com> - 2015-11-03 12:29 +0100
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-03 19:23 +0100
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-03 20:44 -0500
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-04 09:48 +0100
Re: Performance JPA Silvio <silvio@internet.com> - 2015-11-04 10:23 +0100
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-04 11:27 +0100
Re: Performance JPA Silvio <silvio@internet.com> - 2015-11-04 12:42 +0100
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-07 22:18 -0500
Re: Performance JPA Silvio <silvio@internet.com> - 2015-11-09 10:43 +0100
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-20 09:13 +0100
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-07 22:12 -0500
Re: Performance JPA Silvio <silvio@internet.com> - 2015-11-09 10:22 +0100
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-10 21:35 -0500
Re: Performance JPA Silvio <silvio@internet.com> - 2015-11-11 11:29 +0100
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-03 20:42 -0500
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-04 11:19 +0100
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-07 22:05 -0500
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-02 20:08 -0500
Re: Performance JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-11-03 07:55 +0100
Re: Performance JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-11-03 20:45 -0500
Re: Performance JPA Lew <lewbloch@gmail.com> - 2015-11-16 14:43 -0800
csiph-web