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https://issues.apache.org/jira/browse/LUCENE-831?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12698196#action_12698196
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Michael McCandless commented on LUCENE-831:
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> I like this idea, but i am a little bit concerned about only one ValueSource
> for the Reader.
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: https://issues.apache.org/jira/browse/LUCENE-831
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Search
> Reporter: Hoss Man
> Assignee: Mark Miller
> Fix For: 3.0
>
> Attachments: ExtendedDocument.java, 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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