Re: [Exist-open] Urgent assistance with locking behaviour of existdb / deadlocking

[Adam R. <ad...@ex...>]

Would it be possible to see a dump of the lock table when that happens
Pieter?

On Wed, 15 Oct 2025 at 12:52, Pieter Lamers via Exist-open <
exi...@li...> wrote:

> Hi Adam,
>
> It is not trivial to create a reproduceable case for the deadlocking
> problem but I am seeing deadlocks all the time when I do not take the
> necessary precautions when updating. I think it has to do with module
> imports. I think the deadlock occurs when the update of a library module is
> attempted which is also holding a read-lock because of an active process.
> Or the other way around: you make a request which involves a library which
> is being updated. At least one of these scenarios and maybe both can break
> my setup.
>
> This does not seem to be Willem's problem tho.
>
> Best,
> Pieter
>
> On 10/14/2025 9:59 AM, Adam Retter wrote:
>
>
> Hi Willem,
>
> In eXist-db 5.x.x and 6.x.x, the XQuery (if stored in the database) is
> treated as any other document, and so it is locked for the duration of
> operations that happen upon it. Unfortunately this means that whilst a
> query is executing the document holding that query will keep a READ lock on
> the document.
>
> A document may have many either a single write lock, or one or more read
> locks. This means that the query can only be updated by one person/client
> at a time, but that multiple clients can run the query in parallel.
>
> I am not sure how a deadlock could occur with this. Can you provide some
> further information about your issue, and how to reproduce it please?
>
> Thanks, Adam.
>
> On Tue, 14 Oct 2025 at 08:53, Willem van der Westhuizen <wi...@kw...>
> wrote:
>
>> Hi
>>
>> We use existdb extensively to run xqueries on our external databases,
>> couchdb and others. We dont use the existdb datastore for our data.
>>
>> We used to run on an old 3.3.3 version of existdb, and recently migrated
>> to 6.2. Since then we have found that existdb locks the xquery that is
>> being executed, causing deadlocks that eventually locks up the server.
>> Is there an easy way to tell existdb to revert to the older locking
>> behaviour that does not lock up the xquery being run?
>>
>>
>> Regards
>>
>> --
>> Willem van der Westhuizen
>> +27 82 9200718
>>
>>
>>
>> _______________________________________________
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>> Exi...@li...
>> https://lists.sourceforge.net/lists/listinfo/exist-open
>>
>
>
> --
> Adam Retter
>
> eXist Core Developer
> { United Kingdom }
> ad...@ex...
>
>
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>
>
> --
> Pieter Lamers
> John Benjamins Publishing Company
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-- 
Adam Retter

eXist Core Developer
{ United Kingdom }
ad...@ex...