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Date: Fri, 17 Jul 2009 01:37:14 -0700 (PDT)
From: "Michael Busch (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=12732407#action_12732407 ] 

Michael Busch commented on LUCENE-1693:
---------------------------------------

{quote}
As CachingTokenFilter has no API to access the cached attributes/tokens directly,
{quote}

Oh true :) well, scratch it from the TODO list...

We knew it'd work conceptually the same for AttributeSource.State; unlike Tee/Sink, which wouldn't even be save to use with the new API if it hadn't the getTokens() method for the reasons I explained above.

{quote]
Another idea would be to clone all attribute impls and then add them to the sink - the factory would then not be used?
{quote}

Yes, I thought about this for a while. It would be nice to have this (i. e. cloning an AttributeSource) in general: you could reduce the costs for initializing the TokenStreams with onlyUseNewAPI=false. We just need to keep a static AttributeSource around, that contains the wrapper and the mappings from the 6 default interfaces. Then instead of constructing it every time we just clone that AttributeSource for new TokenStreams.

The query parser could do the same to keep initialization costs of the TokenStreams minimal, because it always needs the same attributes.

I think it should be easy? We just need to implement clone() for AttributeSource. 

> 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, LUCENE-1693.patch, LUCENE-1693.patch, LUCENE-1693.patch, LUCENE-1693.patch, LUCENE-1693.patch, LUCENE-1693.patch, lucene-1693.patch, TestAPIBackwardsCompatibility.java, TestCompatibility.java, 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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