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From "Michael Busch (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1693) AttributeSource/TokenStream API improvements
Date Tue, 16 Jun 2009 10:29:07 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12720046#action_12720046
] 

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

{quote}
Why do you add a new class "SmallToken"? I think it should be the good old deprecated "Token".

{quote}

I should have added a "no commit" comment to SmallToken. I just used it for performance tests,
we don't have to commit it. It's an example of what an advanced user could do to speed up
cloning. Token is still there and unchanged.

{quote}
In my opinion, I would not deprecate the old Token, instead the default factory should always
create Token instead of all these default *Impl attributes.
{quote}

Yeah we shouldn't deprecate Token. Not sure about the default. It kind of depends on the use
case. Cloning and memory is faster I think with only two or three Attributes compared to using
the Token cloning is faster. But it'd be simpler to not have all the Impl classes... hmm not
sure... 

{quote}
What was your concusion about my idea yesterday, to pass the Token around even with the old
API and copy it on demand
{quote}

I don't think the indexer should know at all about Token? It should only use the interfaces
so that we can maintain the full flexibility.
Also I don't really like the fact very much that some user might get a performance hit. I
had the idea to throw the exception in incrementToken() to automatically being able to fallback
to the old API. I think this is nice and gets rid of the explicit useNewAPI methods. The only
drawback is still the fact that we have to implement both old and new APIs in Lucene's tokenizers
and filters until we remove the old API. Grant won't like this :) but I think this is better
than the possible performance hit? Also we don't add new filters THAT often to Lucene and
implementing both methods is often mostly copy&paste.

Do you like the idea with the UnsupportedOperationException?


> 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
>
>
> 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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