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From "Michael McCandless (JIRA)" <>
Subject [jira] Commented: (LUCENE-831) Complete overhaul of FieldCache API/Implementation
Date Sun, 12 Apr 2009 09:22:14 GMT


Michael McCandless commented on LUCENE-831:

> I like this idea, but i am a little bit concerned about only one ValueSource for the

Thinking more about this...

Over in KS/Lucy, the approach Marvin is taking is something called a
FieldSpec, to define the "extended type" for a field.  The idea is to
strongly decouple a field's type from its value, allowing that type to
be shared across different fields & instances of the same field.

So in KS/Lucy, presumably IndexReader would simply consult the
FieldSpec for a given field, to determine which ValueSource impl is
responsible for producing values for this field.

Right now details for a field are scattered about (PerFieldValueSource
and PerFieldAnalyzerWrapper and Field.Index/Store/TermVector.*,
FieldInfo, etc.). This then requires alot of app-level code to
properly use Trie* fields -- you have to use Trie* to analyze the
field, use Trie* to construct the query, use PerFieldValueSource to
populate the FieldCache, etc.

Maybe, as part of the cleanup of our three *Field classes, and index
vs search time documents, we should make steps towards having a
consolidated class that represents the "extended type" of a field.
Then in theory one could make a Field, attach a NumericFieldType() to
it (after renaming Trie* -> Numeric*), and then everything would
default properly.

> Complete overhaul of FieldCache API/Implementation
> --------------------------------------------------
>                 Key: LUCENE-831
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>            Reporter: Hoss Man
>            Assignee: Mark Miller
>             Fix For: 3.0
>         Attachments:, fieldcache-overhaul.032208.diff, fieldcache-overhaul.diff,
fieldcache-overhaul.diff, LUCENE-831.03.28.2008.diff, LUCENE-831.03.30.2008.diff, LUCENE-831.03.31.2008.diff,
LUCENE-831.patch, LUCENE-831.patch, LUCENE-831.patch, LUCENE-831.patch, LUCENE-831.patch,
LUCENE-831.patch, LUCENE-831.patch
> Motivation:
> 1) Complete overhaul the API/implementation of "FieldCache" type things...
>     a) eliminate global static map keyed on IndexReader (thus
>         eliminating synch block between completley independent IndexReaders)
>     b) allow more customization of cache management (ie: use 
>         expiration/replacement strategies, disk backed caches, etc)
>     c) allow people to define custom cache data logic (ie: custom
>         parsers, complex datatypes, etc... anything tied to a reader)
>     d) allow people to inspect what's in a cache (list of CacheKeys) for
>         an IndexReader so a new IndexReader can be likewise warmed. 
>     e) Lend support for smarter cache management if/when
>         IndexReader.reopen is added (merging of cached data from subReaders).
> 2) Provide backwards compatibility to support existing FieldCache API with
>     the new implementation, so there is no redundent caching as client code
>     migrades to new API.

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