[infinispan-issues] [JBoss JIRA] (ISPN-5103) Inefficient index updates cause high cost merges and increase overall latency

[Sanne Grinovero (JIRA)]

    [ https://issues.jboss.org/browse/ISPN-5103?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13029921#comment-13029921 ] 

Sanne Grinovero commented on ISPN-5103:
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+1 to revive this discussion.
The reason that Hibernate Search can be more efficient (when using mapped Hibernate entities) is that it has a comprehensive knowledge of which entities are mapped to the current index, so for example it's possible to define if a delete by keyword is doable (it is safe to do when it's known that the index contains no mixed class hierarchies).

I'd be tempted to introduce some limitations to Infinispan Query, for example it would be very helpful to remove a lot of complexity (and inefficiencies like this one) to reject any mapping which would allow multiple entity types to be stored in the same index.
Another benefit would be in the internal engine code, as for example today it's not possible to compute correctly an override for the {{Similarity}} strategy is this is - for example - defined on a parent indexed class which was only added to the known indexed types after its children: {{Similarity}} can't be changed per-type and needs to apply to the whole index consistently from initial index usage.

> Inefficient index updates cause high cost merges and increase overall latency
> -----------------------------------------------------------------------------
>
>                 Key: ISPN-5103
>                 URL: https://issues.jboss.org/browse/ISPN-5103
>             Project: Infinispan
>          Issue Type: Enhancement
>          Components: Embedded Querying
>    Affects Versions: 7.0.2.Final, 7.1.0.Alpha1
>            Reporter: Gustavo Fernandes
>
> Currently every change to the index is done Lucene-wise combining two operations:
> * Delete by query, using a boolean query on the id plus the entity class
> * Add 
>  
> Under high load, specially during merges those numerous deletes provoke very long delays causing high latency. 
> We should instead use a simple Lucene Update to add/change documents, since internally it translates to a Delete by term plus an Add operation, and delete by terms are extremely efficient in Lucene.
> Some local tests showed average latency of updating the index using this strategy to drop 4 times, both for the SYNC and ASYNC  backends
> With relation to sharing the index between entities, which was the original motivation of the Delete by query plus add strategy, we have two scenarios:
> * Same cache with muliple entity types: that's a non-issue, since obviously there's no id colision in this case
> * Different caches with the same index: this scenario happens when different caches shares the same index, for ex:
> {code}
> @Indexed(indeName=common)
> public class Country { ... }
> @Indexed(indeName=common)
> public class Currency { ... }
> cm.getCache("currencies").put(1, new Currency(...))
> cm.getCache("countries").put(1, new Country(...))
> {code}
> This would require a delete by query in order to persist both a Country and a Currency with id=1.
> It would also require setting "default.exclusive_index_use", "false", with the associated cost of having to reopen the IndexWriter on every operation.
> Given the performance gain of doing a simple Update is considerable, we should make the corner case supported by extra configuration or alternatively,  generate a unique @ProvidedId, including the entity class or the cache name that work for all cases described above.



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