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From "Uwe Schindler (JIRA)" <>
Subject [jira] Updated: (LUCENE-1693) AttributeSource/TokenStream API improvements
Date Wed, 17 Jun 2009 12:24:07 GMT


Uwe Schindler updated LUCENE-1693:

    Attachment: LUCENE-1693.patch

Attached is a new patch, that implements the last idea:
- There is no more copying of Tokens, so the API should have the same speed (almost) as before.
- Per default, the chain of TokenStreams/TokenFilters can be mixed completely (test that explicitely
tests this is still missing), the drawback is, that there is only *one* attribute instance
called TokenWrapper (package private) that manages the exchange of the Token instance behind.
- If the user knows, that all tokenizers in his JVM implement incrementToken and do not fallback
to next(), he can increase speed by using the static setter setOnlyUseNewAPI(true). In this
case, no single TokenWrapper is initialized and code will use the normal Attribute factory
to generate the Attributes. If some old code is still available or your consumer calls next(),
you will get an UOE during tokenization. The same happens, if you override initialize() and
instantiate your attributes manually without super.initialize().
- When the old API is removed, TokenWrapper and large parts inside TokenStream can be removed
and incrementToken() made abstract. This is identical to setting onlyUseNewAPI to true.
- the api setting can only be static, because the attribute instances are generated during
construction of the streams and so a later downgrade to TokenWrapper is not possible.

Documentation inside this patch enforce, that at least all core tokenizers and consumers are
conformant, so one must be able to set TokenStream.setOnlyUseNewAPI to true and then use StandardAnalyzer
without any problem. When contrib is transformed, we can extend this to contrib.

Because the code wraps the old API completely, all converted streams can be changed to only
implement only incrementToken() using attributes. Super's and next(Token)
manage the rest. There is no speed degradion by this, it is safe to remove (and all will be


> AttributeSource/TokenStream API improvements
> --------------------------------------------
>                 Key: LUCENE-1693
>                 URL:
>             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,
> 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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