[
https://issues.apache.org/jira/browse/LUCENE-1458?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12783496#action_12783496
]
Uwe Schindler commented on LUCENE-1458:
---------------------------------------
bq. because it compares from left to right, so even if the terms are 10x as
long, if they differ 2x as quick its better?
It would not compare faster because in UTF-8 encoding, only 7 bits are used for
encoding the chars. The 8th bit is just a marker (simply spoken). If this
marker is always 0 or always 1 does not make a difference, in UTF-8 only 7
bits/byte are used for data. And with UTF-8 in the 3rd byte more bits are
unused!
bq. I hear what you are saying about ASCII-only encoding, but if NRQ's model is
always best, why do we have two separate "encode byte[] into char[]" models in
lucene, one that NRQ is using, and one that collation is using!?
I do not know who made this IndexableBinaryStrings encoding, but it would not
work for NRQ at all with current trunk (too complicated during indexing and
decoding, because for NRQ, we also need to decode such char[] very fast for
populating the FieldCache). But as discussed with Yonik (do not know the
issue), the ASCII only encoding should always perform better (but needs more
memory in trunk, as char[] is used during indexing -- I think because of that
it was added). So the difference is not speed, its memory consumption.
> 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.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
---------------------------------------------------------------------
To unsubscribe, e-mail: java-dev-unsubscr...@lucene.apache.org
For additional commands, e-mail: java-dev-h...@lucene.apache.org
