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https://issues.apache.org/jira/browse/LUCENE-2917?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Robert Muir updated LUCENE-2917:
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Fix Version/s: (was: Bulk Postings branch)
5.0
> callers should be able to advance()/jump() without fear
> -------------------------------------------------------
>
> Key: LUCENE-2917
> URL: https://issues.apache.org/jira/browse/LUCENE-2917
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Robert Muir
> Fix For: 5.0
>
>
> Currently, in various places in the code (TermScorer, ExactPhraseScorer)
> there are optimizations
> that assume advance/jump is heavy, and for short doc-distances etc, they
> next() their way instead.
> This sort of logic should instead be in the codec: jump/advance should always
> be fast.
> Its the codecs responsibility to make this happen: jump/advance need not
> involve using skip data.
> For example: in the fixed layout from LUCENE-2905, various forms of
> block-skipping can take place
> to do this operation without skip data (this is implemented in its docs and
> docsAndPositionsEnums,
> but not yet its bulk postings enums).
> For block codecs, they should always avoid trying to skip if the target is
> likely within-block,
> and if the target is likely only a few blocks away, it can still be faster
> not to skip, as skipping
> out of block requires several fills. In the fixed layout we can do these sort
> of 'fast scans' where
> in the docsenum case, we keep the freqs buffer one step behind the docs
> buffer, skipping it when
> we pass over it, and only filling freqs a single time at the end... in the
> docsandpositions case
> we can do the exact same thing with positions.
> I think as part of this, we should tighten the API for the bulkpostings jump,
> it should require the
> current doc (the old enums knew this implicitly) to allow for different jump
> impls. For positions
> i think its at least fair to require the caller to pass in the pending
> positions count.
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