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Date: Wed, 24 Jun 2009 13:43:07 -0700 (PDT)
From: "Uwe Schindler (JIRA)" <jira@apache.org>
To: java-dev@lucene.apache.org
Subject: [jira] Commented: (LUCENE-1693) AttributeSource/TokenStream API
 improvements
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    [ https://issues.apache.org/jira/browse/LUCENE-1693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12723727#action_12723727 ] 

Uwe Schindler commented on LUCENE-1693:
---------------------------------------

In your example, you mean SinkTokenizer is from the core and only implements incrementToken(), the others are handles by the default in TokenStream (using this reflection-based redirect?)

I tested this with overriding LowerCaseFilter. In my latest patch LowerCaseFilter only implements incrementToken(), next() and next(Token) are handled by the forwarder in TokenStream. If you override next(Token) and consume this stream using incrementToken(), then your overriden next(Token) is never called.

This exact same backwards-compatibility problem was also there when changed from next() to next(Token). If some core filter only implemented next(Token) and a subclass overrides only next() (because older code-base) and calls super() there, the same happened: the tokenizer code called next(Token), but next() was never called. You have the same problem with our recent deprecations in DocIdSetIterator.

I would no see this as a problem, this problem can be found everywhere in Lucene, where we deprecated methods and replaced by newer ones calling the old ones as default.


> AttributeSource/TokenStream API improvements
> --------------------------------------------
>
>                 Key: LUCENE-1693
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1693
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Analysis
>            Reporter: Michael Busch
>            Assignee: Michael Busch
>            Priority: Minor
>             Fix For: 2.9
>
>         Attachments: LUCENE-1693.patch, LUCENE-1693.patch, LUCENE-1693.patch, LUCENE-1693.patch, LUCENE-1693.patch, LUCENE-1693.patch, lucene-1693.patch, TestCompatibility.java, TestCompatibility.java, TestCompatibility.java
>
>
> This patch makes the following improvements to AttributeSource and
> TokenStream/Filter:
> - removes the set/getUseNewAPI() methods (including the standard
>   ones). Instead by default incrementToken() throws a subclass of
>   UnsupportedOperationException. The indexer tries to call
>   incrementToken() initially once to see if the exception is thrown;
>   if so, it falls back to the old API.
> - introduces interfaces for all Attributes. The corresponding
>   implementations have the postfix 'Impl', e.g. TermAttribute and
>   TermAttributeImpl. AttributeSource now has a factory for creating
>   the Attribute instances; the default implementation looks for
>   implementing classes with the postfix 'Impl'. Token now implements
>   all 6 TokenAttribute interfaces.
> - new method added to AttributeSource:
>   addAttributeImpl(AttributeImpl). Using reflection it walks up in the
>   class hierarchy of the passed in object and finds all interfaces
>   that the class or superclasses implement and that extend the
>   Attribute interface. It then adds the interface->instance mappings
>   to the attribute map for each of the found interfaces.
> - AttributeImpl now has a default implementation of toString that uses
>   reflection to print out the values of the attributes in a default
>   formatting. This makes it a bit easier to implement AttributeImpl,
>   because toString() was declared abstract before.
> - Cloning is now done much more efficiently in
>   captureState. The method figures out which unique AttributeImpl
>   instances are contained as values in the attributes map, because
>   those are the ones that need to be cloned. It creates a single
>   linked list that supports deep cloning (in the inner class
>   AttributeSource.State). AttributeSource keeps track of when this
>   state changes, i.e. whenever new attributes are added to the
>   AttributeSource. Only in that case will captureState recompute the
>   state, otherwise it will simply clone the precomputed state and
>   return the clone. restoreState(AttributeSource.State) walks the
>   linked list and uses the copyTo() method of AttributeImpl to copy
>   all values over into the attribute that the source stream
>   (e.g. SinkTokenizer) uses. 
> The cloning performance can be greatly improved if not multiple
> AttributeImpl instances are used in one TokenStream. A user can
> e.g. simply add a Token instance to the stream instead of the individual
> attributes. Or the user could implement a subclass of AttributeImpl that
> implements exactly the Attribute interfaces needed. I think this
> should be considered an expert API (addAttributeImpl), as this manual
> optimization is only needed if cloning performance is crucial. I ran
> some quick performance tests using Tee/Sink tokenizers (which do
> cloning) and the performance was roughly 20% faster with the new
> API. I'll run some more performance tests and post more numbers then.
> Note also that when we add serialization to the Attributes, e.g. for
> supporting storing serialized TokenStreams in the index, then the
> serialization should benefit even significantly more from the new API
> than cloning. 
> Also, the TokenStream API does not change, except for the removal 
> of the set/getUseNewAPI methods. So the patches in LUCENE-1460
> should still work.
> All core tests pass, however, I need to update all the documentation
> and also add some unit tests for the new AttributeSource
> functionality. So this patch is not ready to commit yet, but I wanted
> to post it already for some feedback. 

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