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From "Uwe Schindler (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1701) Add NumericField and NumericSortField, make plain text numeric parsers public in FieldCache, move trie parsers to FieldCache
Date Fri, 19 Jun 2009 18:08:07 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1701?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12721914#action_12721914
] 

Uwe Schindler commented on LUCENE-1701:
---------------------------------------

Yonik, I will explain my intention:
The real numeric parsing is always done in NumericUtils, as for conventional FieldCache the
real parsing is done in Integer.parseInt() and so on.
Specific to the FieldCache is the Parser interface. This parser interface is a java interface
specific to FieldCache. FieldCache currently has (private) static parser instances for Number.toString()-type
fields. These parser are simple 5-liners and singletons. For trie fields, this is the same,
the static parser instances (also singletons) should be moved also to FieldCache, after that
both as public constants (like Mike said: PLAIN_TEXT_INT_PARSER and NUMERIC_INT_PARSER).
Currently for Trie fields there is a ugly hack in FieldCache, that stops parsing, when a term
with lower precision is reached (as trie terms are ordered with highest precision first, the
cache for a field is filled, when the first lower-precision term comes). Because of this,
the trie parsers throw a unchecked StopFillCacheException to stop the iteration of TermEnum/TermDocs
in the Uninverter. This is just a hack and because of package differences this FieldCache-internal
exception is made public (see Javadocs). When moving the parser interfaces to FieldCace, this
Exception can be hidden again and made private to the FieldCache implementation (until we
have the better univerters some time in future, see LUCENE-831). NumericUtils then will only
just export a method to get the shift value out of a encoded string (which I forgot to add
in LUCENE-1673 when removing ShiftAttribute).
Trie field parsing does not depend on Trie-specific flags, precisionStep is not needed, so
the parsers are real singletons.

SortFields can then simply created in the Following way: new SortField(field, FieldCache.PLAIN_TEXT_INT_PARSER)
for a conventional int field (like with SortField.INT) or new SortField(field, FieldCache.NUMERIC_INT_PARSER).
giving a NULL parser still does the same as before, it uses FieldCache.PLAIN_TEXT_INT_PARSER
implicitely.

> Add NumericField and NumericSortField, make plain text numeric parsers public in FieldCache,
move trie parsers to FieldCache
> ----------------------------------------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-1701
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1701
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: Index, Search
>    Affects Versions: 2.9
>            Reporter: Uwe Schindler
>            Assignee: Uwe Schindler
>             Fix For: 2.9
>
>         Attachments: NumericField.java
>
>
> In discussions about LUCENE-1673, Mike & me wanted to add a new NumericField to o.a.l.document
specific for easy indexing. An alternative would be to add a NumericUtils.newXxxField() factory,
that creates a preconfigured Field instance with norms and tf off, optionally a stored text
(LUCENE-1699) and the TokenStream already initialized. On the other hand NumericUtils.newXxxSortField
could be moved to NumericSortField.
> I and Yonik tend to use the factory for both, Mike tends to create the new classes.
> Also the parsers for string-formatted numerics are not public in FieldCache. As the new
SortField API (LUCENE-1478) makes it possible to support a parser in SortField instantiation,
it would be good to have the static parsers in FieldCache public available. SortField would
init its member variable to them (instead of NULL), so making code a lot easier (FieldComparator
has this ugly null checks when retrieving values from the cache).
> Moving the Trie parsers also as static instances into FieldCache would make the code
cleaner and we would be able to hide the "hack" StopFillCacheException by making it private
to FieldCache (currently its public because NumericUtils is in o.a.l.util).

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