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From "Simon Willnauer (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2186) First cut at column-stride fields (index values storage)
Date Tue, 30 Nov 2010 14:50:12 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2186?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12965242#action_12965242
] 

Simon Willnauer commented on LUCENE-2186:
-----------------------------------------

bq. Is there any test cases that cover the new FieldComparators that use the doc values?
not yet, I added it to my internal roadmap to land on trunk. I just committed my latest changes
including a simple testcase to show how to use the API and used bytes tracking. 

here is a list of what is missing:

{code}
  /*
   * TODO:
   * Roadmap to land on trunk
   *   - Cut over to a direct API on ValuesEnum vs. ValuesAttribute 
   *   - Add documentation for:
   *      - Source and ValuesEnum
   *      - DocValues
   *      - ValuesField
   *      - ValuesAttribute
   *      - Values
   *   - Add @lucene.experimental to all necessary classes
   *   - Try to make ValuesField more lightweight -> AttributeSource
   *   - add test for unoptimized case with deletes
   *   - add a test for addIndexes
   *   - split up existing testcases and give them meaningfull names
   *   - use consistent naming throughout DocValues
   *     - Values -> DocValueType
   *     - PackedIntsImpl -> Ints
   *   - run RAT
   *   - add tests for FieldComparator FloatIndexValuesComparator vs. FloatValuesComparator
etc.
   */
{code}

once I am through with it I will create a new issue and create the final patch so we can iterate
over it if needed.

simon

> First cut at column-stride fields (index values storage)
> --------------------------------------------------------
>
>                 Key: LUCENE-2186
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2186
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: Index
>            Reporter: Michael McCandless
>            Assignee: Simon Willnauer
>             Fix For: CSF branch, 4.0
>
>         Attachments: LUCENE-2186.patch, LUCENE-2186.patch, LUCENE-2186.patch, LUCENE-2186.patch,
LUCENE-2186.patch, mem.py
>
>
> I created an initial basic impl for storing "index values" (ie
> column-stride value storage).  This is still a work in progress... but
> the approach looks compelling.  I'm posting my current status/patch
> here to get feedback/iterate, etc.
> The code is standalone now, and lives under new package
> oal.index.values (plus some util changes, refactorings) -- I have yet
> to integrate into Lucene so eg you can mark that a given Field's value
> should be stored into the index values, sorting will use these values
> instead of field cache, etc.
> It handles 3 types of values:
>   * Six variants of byte[] per doc, all combinations of fixed vs
>     variable length, and stored either "straight" (good for eg a
>     "title" field), "deref" (good when many docs share the same value,
>     but you won't do any sorting) or "sorted".
>   * Integers (variable bit precision used as necessary, ie this can
>     store byte/short/int/long, and all precisions in between)
>   * Floats (4 or 8 byte precision)
> String fields are stored as the UTF8 byte[].  This patch adds a
> BytesRef, which does the same thing as flex's TermRef (we should merge
> them).
> This patch also adds basic initial impl of PackedInts (LUCENE-1990);
> we can swap that out if/when we get a better impl.
> This storage is dense (like field cache), so it's appropriate when the
> field occurs in all/most docs.  It's just like field cache, except the
> reading API is a get() method invocation, per document.
> Next step is to do basic integration with Lucene, and then compare
> sort performance of this vs field cache.
> For the "sort by String value" case, I think RAM usage & GC load of
> this index values API should be much better than field caache, since
> it does not create object per document (instead shares big long[] and
> byte[] across all docs), and because the values are stored in RAM as
> their UTF8 bytes.
> There are abstract Writer/Reader classes.  The current reader impls
> are entirely RAM resident (like field cache), but the API is (I think)
> agnostic, ie, one could make an MMAP impl instead.
> I think this is the first baby step towards LUCENE-1231.  Ie, it
> cannot yet update values, and the reading API is fully random-access
> by docID (like field cache), not like a posting list, though I
> do think we should add an iterator() api (to return flex's DocsEnum)
> -- eg I think this would be a good way to track avg doc/field length
> for BM25/lnu.ltc scoring.

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