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https://issues.apache.org/jira/browse/LUCENE-5052?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13689544#comment-13689544
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David Smiley commented on LUCENE-5052:
--------------------------------------
Yeah cool idea. But I feel that to truly take the performance to the next
level, there should be a way to intersect the bit vector with another. The
spatial Lucene filters have loops that work by populating a FixedBitSet by
looping over DocsEnum. But if behind the scene's it's just another bitset, I
would love to efficiently union the bitsets. Example snippet of existing code:
{code:java}
int docid;
while ((docid = docsEnum.nextDoc()) != DocIdSetIterator.NO_MORE_DOCS) {
bitSet.set(docid);
}
{code}
I'd bet there's a lot of code like this around.
> bitset codec for off heap filters
> ---------------------------------
>
> Key: LUCENE-5052
> URL: https://issues.apache.org/jira/browse/LUCENE-5052
> Project: Lucene - Core
> Issue Type: New Feature
> Components: core/codecs
> Reporter: Mikhail Khludnev
> Labels: features
> Fix For: 5.0
>
>
> Colleagues,
> When we filter we don’t care any of scoring factors i.e. norms, positions,
> tf, but it should be fast. The obvious way to handle this is to decode
> postings list and cache it in heap (CachingWrappingFilter, Solr’s DocSet).
> Both of consuming a heap and decoding as well are expensive.
> Let’s write a posting list as a bitset, if df is greater than segment's
> maxdocs/8 (what about skiplists? and overall performance?).
> Beside of the codec implementation, the trickiest part to me is to design API
> for this. How we can let the app know that a term query don’t need to be
> cached in heap, but can be held as an mmaped bitset?
> WDYT?
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