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Date: Sun, 29 Nov 2009 22:29:20 +0000 (UTC)
From: "Michael McCandless (JIRA)" <jira@apache.org>
To: java-dev@lucene.apache.org
Subject: [jira] Commented: (LUCENE-1458) Further steps towards flexible
 indexing
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    [ https://issues.apache.org/jira/browse/LUCENE-1458?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12783492#action_12783492 ] 

Michael McCandless commented on LUCENE-1458:
--------------------------------------------

bq. I changed the logic in the TermEnum in trunk and 3.0 (it no longer works recursive, see LUCENE-2087). We should change this here, too.

Mark has been periodically re-syncing changes down from trunk... we should probably just let this change come in through his process (else I think we cause more conflicts).

bq. The legacy NumericRangeTermEnum can be removed completely and the protected getEnum() should simply throw UOE. NRQ cannot be subclassed and nobody can call this method (maybe only classes in same package, but thats not supported). So the enum with the nocommit mark can be removed

Ahh excellent.  Wanna commit that when you get a chance?

bq.  Ideally NRQ would simply not use string terms at all and work directly on the byte[], which should then be ordered in binary order.

That'd be great!

bq. With directly on bytes[] I meant that it could not use chars at all and directly encode the numbers into byte[] with the full 8 bits per byte. The resulting byte[] would be never UTF-8, but if the new TermRef API would be able to handle this and also the TokenStreams, it would be fine. Only the terms format would change.

Right, this is a change in analysis -> DocumentsWriter -- somehow we have to allow a Token to carry a byte[] and that is directly indexes as the opaque term.  At search time NRQ is all byte[] already (unlike other queries, which are new String()'ing for every term on the enum).

> Further steps towards flexible indexing
> ---------------------------------------
>
>                 Key: LUCENE-1458
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1458
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: Index
>    Affects Versions: 2.9
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>            Priority: Minor
>         Attachments: LUCENE-1458-back-compat.patch, LUCENE-1458-back-compat.patch, LUCENE-1458-back-compat.patch, LUCENE-1458-back-compat.patch, LUCENE-1458-back-compat.patch, LUCENE-1458-back-compat.patch, LUCENE-1458.patch, LUCENE-1458.patch, LUCENE-1458.patch, LUCENE-1458.patch, LUCENE-1458.patch, LUCENE-1458.patch, LUCENE-1458.patch, LUCENE-1458.patch, LUCENE-1458.patch, LUCENE-1458.patch, LUCENE-1458.patch, LUCENE-1458.patch, LUCENE-1458.patch, LUCENE-1458.tar.bz2, LUCENE-1458.tar.bz2, LUCENE-1458.tar.bz2, LUCENE-1458.tar.bz2, LUCENE-1458.tar.bz2, LUCENE-1458.tar.bz2, LUCENE-1458.tar.bz2, LUCENE-1458_sortorder_bwcompat.patch, LUCENE-1458_termenum_bwcompat.patch, UnicodeTestCase.patch, UnicodeTestCase.patch
>
>
> I attached a very rough checkpoint of my current patch, to get early
> feedback.  All tests pass, though back compat tests don't pass due to
> changes to package-private APIs plus certain bugs in tests that
> happened to work (eg call TermPostions.nextPosition() too many times,
> which the new API asserts against).
> [Aside: I think, when we commit changes to package-private APIs such
> that back-compat tests don't pass, we could go back, make a branch on
> the back-compat tag, commit changes to the tests to use the new
> package private APIs on that branch, then fix nightly build to use the
> tip of that branch?o]
> There's still plenty to do before this is committable! This is a
> rather large change:
>   * Switches to a new more efficient terms dict format.  This still
>     uses tii/tis files, but the tii only stores term & long offset
>     (not a TermInfo).  At seek points, tis encodes term & freq/prox
>     offsets absolutely instead of with deltas delta.  Also, tis/tii
>     are structured by field, so we don't have to record field number
>     in every term.
> .
>     On first 1 M docs of Wikipedia, tii file is 36% smaller (0.99 MB
>     -> 0.64 MB) and tis file is 9% smaller (75.5 MB -> 68.5 MB).
> .
>     RAM usage when loading terms dict index is significantly less
>     since we only load an array of offsets and an array of String (no
>     more TermInfo array).  It should be faster to init too.
> .
>     This part is basically done.
>   * Introduces modular reader codec that strongly decouples terms dict
>     from docs/positions readers.  EG there is no more TermInfo used
>     when reading the new format.
> .
>     There's nice symmetry now between reading & writing in the codec
>     chain -- the current docs/prox format is captured in:
> {code}
> FormatPostingsTermsDictWriter/Reader
> FormatPostingsDocsWriter/Reader (.frq file) and
> FormatPostingsPositionsWriter/Reader (.prx file).
> {code}
>     This part is basically done.
>   * Introduces a new "flex" API for iterating through the fields,
>     terms, docs and positions:
> {code}
> FieldProducer -> TermsEnum -> DocsEnum -> PostingsEnum
> {code}
>     This replaces TermEnum/Docs/Positions.  SegmentReader emulates the
>     old API on top of the new API to keep back-compat.
>     
> Next steps:
>   * Plug in new codecs (pulsing, pfor) to exercise the modularity /
>     fix any hidden assumptions.
>   * Expose new API out of IndexReader, deprecate old API but emulate
>     old API on top of new one, switch all core/contrib users to the
>     new API.
>   * Maybe switch to AttributeSources as the base class for TermsEnum,
>     DocsEnum, PostingsEnum -- this would give readers API flexibility
>     (not just index-file-format flexibility).  EG if someone wanted
>     to store payload at the term-doc level instead of
>     term-doc-position level, you could just add a new attribute.
>   * Test performance & iterate.

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