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https://issues.apache.org/jira/browse/LUCENE-1911?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12756180#action_12756180
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Uwe Schindler commented on LUCENE-1911:
---------------------------------------

I understand you, but:

After reviewing other DocIdSets, I found more of them, that could be easily 
cached, like e.g. one of the DocIdSets returned by FieldCacheRangeFilter (the 
only-FieldCache-non-TermDocs-backed one). You cannot check all of them with 
instanceof and may some of them twice, which is a bad idea. A simple check with 
DocIdSet.isCacheable() looks like a good solution. If we default it to false, 
we have no backwards-problem.

If we do not want to do this, I will add at least SortedVIntList to the 
cacheable implementations.

> When using QueryWrapperFilter with CachingWrapperFilter, QueryWrapperFilter 
> returns a DocIdSet that creates a Scorer, which gets cached rather than a bit 
> set
> -------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-1911
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1911
>             Project: Lucene - Java
>          Issue Type: Bug
>            Reporter: Mark Miller
>            Assignee: Uwe Schindler
>             Fix For: 2.9
>
>         Attachments: LUCENE-1911.patch
>
>
> there is a large performance cost to this.
> The old impl for this type of thing, QueryFilter, recommends :
> @deprecated use a CachingWrapperFilter with QueryWrapperFilter
> The deprecated QueryFilter itself also suffers from the problem because its 
> now implemented using a CachingWrapperFilter and QueryWrapperFilter.
> see 
> http://search.lucidimagination.com/search/document/7f54715f14b8b7a/lucene_2_9_0rc4_slower_than_2_4_1

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