Re: [keycloak-dev] @Column.updatable=false
The updatable=false causes the column not to be in UPDATE statements
which is beneficial for several reasons:
* UPDATEs update less columns - thats always positive
* Database vendor _might_ (and some do) take advantage of the affected
columns list in UPDATE to eliminate even the need to check whether
related index needs to be updated instead of checking whether the
values match
* There _might_ be optimizations on Hibernate side that would help.
I'd need to dive more into actual details as I'd rather expect that it
would show up if we used Hibernate caching.
Yet the performance might actually improve even more by using
@DynamicUpdate annotation on JPA entities. The @DynamicUpdate would do
the job the Column.updatable does, in a less-prohibitive way, still
allowing the updates but only including the changed fields in the
result UPDATE. I'd imagine that would be most beneficial on
UserEntity.
--Hynek
On Mon, Sep 11, 2017 at 4:04 PM, Bill Burke <bburke(a)redhat.com> wrote:
This popped up in a support request, but we have a number of foreign
keys (with indexes) that are never changed, but yet are included in
update requests of those tables by Hibernate. It seems that a number
of databases (and Hibernate, although don't know if there is a setting
for that) will not check to see if the old value equals new value.
This can cause concurrency issues (db deadlock). I bet it is a big
performance issue too if indexes are updated as well.
Should this be bumped to a priority for 3.4.1? I'll create a JIRA if so.
--
Bill Burke
Red Hat
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--Hynek