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https://issues.apache.org/jira/browse/LUCENE-3443?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13146465#comment-13146465
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Yonik Seeley commented on LUCENE-3443:
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bq. Ie, there's no guarantee w/in trunk that performance won't "change",
Of course not. I'm arguing a specific point though: that we shouldn't double
time time it takes solr users to instantiate field caches (or other lucene
users that regularly use sortMissingLast). "we can do it later" is not a good
argument to remove existing functionality.
bq. > Or we could generate the bits by default - the extra cache entry if not
needed is less serious than doubling the generation time.
I mean, generate the bits by default until the two-pass problem is fixed (not
forever).
bq. I'd rather not do that; apps that don't use sort missing first/last
shouldn't be forced to spend the RAM (even if it's only a bit per doc).
But it's trunk, right? There's no guarantee w/in trunk that performance won't
"change" ;-)
Using 1/32 more memory (3%) is way less evil than doubling field cache entry
times.
bq. Also, this (uniqueTermCount) is redundant with Terms.getUniqueTermCount()?
Not for numeric fields, where a precisionStep causes nTerms > nUniqueValues
> Port 3.x FieldCache.getDocsWithField() to trunk
> -----------------------------------------------
>
> Key: LUCENE-3443
> URL: https://issues.apache.org/jira/browse/LUCENE-3443
> Project: Lucene - Java
> Issue Type: Improvement
> Components: core/search
> Reporter: Michael McCandless
> Assignee: Michael McCandless
> Fix For: 3.5, 4.0
>
> Attachments: LUCENE-3443.patch
>
>
> [Spinoff from LUCENE-3390]
> I think the approach in 3.x for handling un-valued docs, and making it
> possible to specify how such docs are sorted, is better than the
> solution we have in trunk.
> I like that FC has a dedicated method to get the Bits for docs with field
> -- easy for apps to directly use. And I like that the
> bits have their own entry in the FC.
> One downside is that it's 2 passes to get values and valid bits, but
> I think we can fix this by passing optional bool to FC.getXXX methods
> indicating you want the bits, and the populate the FC entry for the
> missing bits as well. (We can do that for 3.x and trunk). Then it's
> single pass.
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