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https://issues.apache.org/jira/browse/LUCENE-5052?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13947085#comment-13947085
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Michael McCandless commented on LUCENE-5052:
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bq. this posting format should wrap the standard one, like pulsing;
I don't think we need to do that (I was convinced, above)? I think it should
just be its own PF, and the app picks it to store all postings as bitsets.
bq. if IndexOptions.DOCS_ONLY is provided, this codec suppresses standard
posting format and write the bitset file (<<should-be>> explore fancy formats
then);
I think it should ONLY accept DOCS_ONLY? Ie, throw an exc if it gets anything
else, because it's mis-use.
bq. I wonder what’s the correct behavior if docEnum is requested with
FLAG_FREQS, should it silently returns 1 on freq() or throwing exception?
I think lie (return 1 from freq).
> 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
>
> Attachments: LUCENE-5052.patch, bitsetcodec.zip, bitsetcodec.zip
>
>
> 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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