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From "Uwe Schindler (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2649) FieldCache should include a BitSet for matching docs
Date Fri, 17 Sep 2010 16:44:35 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2649?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12910654#action_12910654
] 

Uwe Schindler commented on LUCENE-2649:
---------------------------------------

I am against the configuration option to enable the additional BitSet. The problem is that
you cannot control it for each usage for the FieldCache, as it is a static flag. We agreed
in the past that we will remove all static defaults from Lucene (e.g. BQ.maxClauseCount) together
with sytem properties. This flag can cause strange problems with 3rd party code (like when
you lower the BQ maxClauseCount and suddenly your queries fail).

The overhead by the OpenBitSet is very marginal (for integers only 1/32, as Yonik said). If
you have memory problems with the FieldCache, these 1/32 would not hurt you, as you should
think about your whole configuration then (liek moving from ints to shorts or something like
that).

So: Please don't add any static defaults or sysprops! Please, please, please!

> FieldCache should include a BitSet for matching docs
> ----------------------------------------------------
>
>                 Key: LUCENE-2649
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2649
>             Project: Lucene - Java
>          Issue Type: Improvement
>            Reporter: Ryan McKinley
>             Fix For: 4.0
>
>         Attachments: LUCENE-2649-FieldCacheWithBitSet.patch, LUCENE-2649-FieldCacheWithBitSet.patch,
LUCENE-2649-FieldCacheWithBitSet.patch
>
>
> The FieldCache returns an array representing the values for each doc.  However there
is no way to know if the doc actually has a value.
> This should be changed to return an object representing the values *and* a BitSet for
all valid docs.

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