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From "Uwe Schindler (JIRA)" <>
Subject [jira] Commented: (LUCENE-2314) Add AttributeSource.copyTo(AttributeSource)
Date Sat, 13 Mar 2010 13:55:27 GMT


Uwe Schindler commented on LUCENE-2314:

Because of speed we do not do this. That was performance tested in 2.9 development. The for-loop
using the linked list directly is far faster. the captureState is one of the most optimized

> Add AttributeSource.copyTo(AttributeSource)
> -------------------------------------------
>                 Key: LUCENE-2314
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>            Reporter: Uwe Schindler
>            Assignee: Uwe Schindler
>            Priority: Minor
>             Fix For: 3.1
>         Attachments: LUCENE-2314.patch
> One problem with AttributeSource at the moment is the missing "insight" into AttributeSource.State.
If you want to create TokenStreams that inspect cpatured states, you have no chance. Making
the contents of State public is a bad idea, as it does not help for inspecting (its a linked
list, so you have to iterate).
> AttributeSource currently contains a cloneAttributes() call, which returns a new AttrubuteSource
with all current attributes cloned. This is the (more expensive) captureState. The problem
is that you cannot copy back the cloned AS (which is the restoreState). To use this behaviour
(by the way, ShingleMatrix can use it), one can alternatively use cloneAttributes and copyTo.
You can easily change the cloned attributes and store them in lists and copy them back. The
only problem is lower performance of these calls (as State is a very optimized class).
> One use case could be:
> {code}
> AttributeSource state = cloneAttributes();
> // .... do something ...
> state.getAttribute(TermAttribute.class).setTermBuffer(foobar);
> // ... more work
> state.copyTo(this);
> {code}

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