About cache size

[Z]

Dear Gerrit Community,

     gerrit version 3.12.4  and  following cache

      git_file_diff-v2.mv.db

      git_modified_files-v2.mv.db

      modified_files-v2.mv.db

       diff_summary-v2.mv.db

       change_kind-v2.mv.db

       web_sessions-v2.mv.db

        gerrit_file_diff-v2.mv.db    

If these caches become unusually large, what problems might that cause?

Thanks.

[Matthias Sohn]

We found that huge persistent h2 caches can lead to OOM errors and that such huge h2 caches
can be caused by offline reindexing the complete changes index.

We mitigated this with https://gerrit-review.googlesource.com/c/gerrit/+/473823 which allows to make persistent
caches read-only during offline reindexing. This feature is available since Gerrit 3.13. 

 

Thanks.

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[Luca Milanesio]

On 2 Mar 2026, at 09:40, Matthias Sohn <matthi...@gmail.com> wrote:

On Mon, Mar 2, 2026 at 10:30 AM Z <vista...@gmail.com> wrote:

Dear Gerrit Community,

     gerrit version 3.12.4  and  following cache

      git_file_diff-v2.mv.db

      git_modified_files-v2.mv.db

      modified_files-v2.mv.db

       diff_summary-v2.mv.db

       change_kind-v2.mv.db

       web_sessions-v2.mv.db

        gerrit_file_diff-v2.mv.db    

If these caches become unusually large, what problems might that cause?

We found that huge persistent h2 caches can lead to OOM errors and that such huge h2 caches
can be caused by offline reindexing the complete changes index.

Yep,

I have also verified that large H2 caches can be *so slow* that running Gerrit without caches would make it faster, which could be counter-intuitive :-)

We mitigated this with https://gerrit-review.googlesource.com/c/gerrit/+/473823 which allows to make persistent
caches read-only during offline reindexing. This feature is available since Gerrit 3.13. 

+1 indeed.

Also, you may want to use a more efficient cache implementation that doesn’t degrade when the size grows.

See [1].

HTH

Luca.

[1] https://github.com/GerritForge/cache-chroniclemap

 

Thanks.

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[Luca Milanesio]

On 2 Mar 2026, at 10:12, Z <vista...@gmail.com> wrote:

Hi,luca:

 Thank you for your reply.

>>>    If the cache-chroniclemap also becomes very large, could it lead to OOM (Out of Memory)?

Nope, that’s the main difference between H2 and cache-chroniclemap.

See the last talk about Gerrit persistent caches options at [2].

HTH

Luca.

[2] https://youtu.be/T2ApofhyF10

Thank you.

Luca Milanesio 在 2026年3月2日 星期一下午5:55:58 [UTC+8] 的信中寫道：