How to limit Java String creation in Hibernate?

Question

We are trying to improve performance in our Java application. While using the Memory Analysis tool, I noticed that there are many duplicate Strings that seem to have originated in Hibernate. For example, the Memory Analysis Tool sees over 6000 occurrences of "rowid_0_" and "0_", and tracing to the GC root shows Hibernate's involvement:

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It seems as though we could improve performance if we could intern those Strings. If it were "our" code, I could modify it and see the effects. Is there any way that I can coerce Hibernate into using interned Strings?

What version of Hibernate are you using? I don't see any new String() in org.hibernate.loader.DefaultEntityAliases. If anything it does intern strings. grepcode.com/file/repository.springsource.com/org.hibernate/… — Steve Kuo
– Steve Kuo, Commented Feb 25, 2014 at 17:02
@Steve Kuo - We are using hibernate-core 3.6.10.Final and hibernate-jpa-2.0-api. Could it be a JPA thing? — kc2001
– kc2001, Commented Feb 25, 2014 at 17:56
@Steve Kuo - On line 87 of the link you provided, I see "rowIdAlias = Loadable.ROWID_ALIAS + suffix;". This may be a culprit. — kc2001
– kc2001, Commented Feb 25, 2014 at 18:19
Yup I see it now, and StringBuilder does indeed create a new String. — Steve Kuo
– Steve Kuo, Commented Feb 25, 2014 at 19:10

kc2001 · Accepted Answer · 2014-02-25 19:22:04Z

1

I now see that the Hibernate issue 3924 refers to this. However, HHH-3924 has a status of "Open", and is unresolved. It does refer to a code patch that interns the rowid Strings.

edited Feb 25, 2014 at 19:22

answered Feb 25, 2014 at 19:02

kc2001

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