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https://issues.apache.org/jira/browse/LUCENE-1693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12720809#action_12720809
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Uwe Schindler commented on LUCENE-1693:
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The code is almost identical to before, the old code also copied the token to
make it a full private copy.
There are three modes of operation:
- if incrementToken is implemented, docinverter will use it (the code always
calls incrementToken, so no indirection)
- if next(Token) is implemented, the docinverterwill call incrementToken which
is forwarded to next(Token), which is cheap
- if only next() is implemented, the docinverter will call incrementTojen,
which forwards to next(Token) and this forwards to next(). But this is
identical to before, only one indirection more: the old code got
useNewAPI(false) and called next(Token) which forwarded to next()
So for indexing using the normal indexing components (docinverter), the code is
never cloning more that with your code.
There is one other case: if you have an old consumer calling nextToken(Token),
the tokenizer only implemented incrementToken, then you will get a performance
degradion. But this is not the indexing case, it is e.g. reusing the tokenizer
in a very old e.g. QueryParser. I did not find a good way to pass directly for
this special case to incrementToken(). The problem is also, that incrementToken
uses the internal buffer and not the supplied buffer.
> 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,
> 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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