Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.lang.java.programmer > #32982
| From | Martin Gregorie <martin@address-in-sig.invalid> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: Performance JPA |
| Date | 2015-11-03 11:16 +0000 |
| Organization | A noiseless patient Spider |
| Message-ID | <n1a51v$4qh$1@dont-email.me> (permalink) |
| References | <87lhagkcsh.fsf@Equus.decebal.nl> <563763d9$0$23727$e4fe514c@news.xs4all.nl> <87d1vrk20x.fsf@Equus.decebal.nl> |
On Tue, 03 Nov 2015 07:52:46 +0100, Cecil Westerhof wrote: > At the moment I am told that everything is slower. I am told that a > query that took at most 5 seconds now takes one to two minutes. But I > asked them to measure the old situation and until now they did not do > this. I hope to get today real data about this. But several pages now > give a timeout. > Usually slow retrievals mean that the DBMS is sequentially scanning tables rather than using indexes, so the obvious starting point is to see how the JPA queries differ from the ones used by JDBC and, if the difference can't be found by inspection, to use the DBMS query cost analysis facilities to run the queries manually and report execution plan used for them. Typically the poor performance is that joins, WHERE or ORDER BY clauses on large tables are not supported by indexes: the solution is to add these indexes to the schema if the query is run frequently enough to justify doing so. 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. Check whether the JPA has debugging/tracing facilities that can be used to show the queries that are being run and and cost or performance data for them. Welcome to the world of RDBMS tuning: I hope your DBA is up to speed on this passtime! -- 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