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From Paul Elschot <>
Subject Fwd: Decouple Filter from BitSet: API change and xml query parser
Date Fri, 10 Aug 2007 07:45:09 GMT
Taking this to java-dev only.

As I said at the jira issue, I'd like to have all test cases pass again,
and I'm not happy with the current version of the patch to the xml query 
parser either.

Some test cases currently fail maybe because they use RMI and the
new version of Filter does serialize well because the result of getMatcher()
is not serializable.
It should be possible to fix this by moving Filter to BitSetFilter in these 
cases, see also below.
The problem is that I don't know how to do this because I have never
used java RMI myself.

Could someone give me a clue as to why the test case
TestRemoteCachingWrapperFilter fails with the patch applied?

As for the API change, how to move from the current:

public class Filter {
  abstract public BitSet bits(IndexReader); 


public class Filter {
  abstract public Matcher getMatcher(IndexReader); 

The patch proposes to do this by moving all current use of Filter to

public class BitSetFilter extends Filter {
  abstract public BitSet bits(IndexReader); 

Would it be good to have an intermediate version of Filter like this

public class Filter {
  /** deprecated, use class BitSetFilter instead */
  public BitSet bits(IndexReader); {return null;}
  abstract public Matcher getMatcher(IndexReader); 

Finally, are DocIdSet and DocIdSetIterator currently part of Lucene?
I don't know how to go about these.

Paul Elschot

----------  Forwarded Message  ----------

Subject: [jira] Commented: (LUCENE-584) Decouple Filter from BitSet
Date: Friday 10 August 2007 01:15
From: "Mark Harwood (JIRA)" <>


Mark Harwood commented on LUCENE-584:

OK, I appreciate caching may not be a top priority in this proposal but I have 
live systems in production using XMLQueryParser and which use the existing 
core facilities for caching. As it stands this proposal breaks this 
functionality (see "FIXME" in contrib's CachedFilterBuilder and my concerns 
over use of  unthreadsafe Matcher in the core class CachingWrapperFilter)

I am obviously concerned by this and keen to help shape a solution which 
preserves the existing capabilities while adding your new functionality. I'm 
not sure I share your view that support for caching can be treated as a 
separate issue to be dealt with at a later date. There are a larger number of 
changes proposed in this patch and if the design does not at least consider 
future caching issues now, I suspect much will have to be reworked later. The 
change I can envisage most clearly is expressed in my concern that the 
DocIdSet and DocIdSetIterator services I outlined are being combined in 
Matcher as it stands now and these functions will have to be separated.


> Decouple Filter from BitSet
> ---------------------------
>                 Key: LUCENE-584
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>    Affects Versions: 2.0.1
>            Reporter: Peter Schäfer
>            Priority: Minor
>         Attachments: bench-diff.txt, bench-diff.txt, 
Matcher1-ground-20070730.patch, Matcher2-default-20070730.patch, 
Matcher3-core-20070730.patch, Matcher4-contrib-misc-20070730.patch, 
Matcher5-contrib-queries-20070730.patch, Matcher6-contrib-xml-20070730.patch, 
> {code}
> package;
> public abstract class Filter implements 
> {
>   public abstract AbstractBitSet bits(IndexReader reader) throws 
> }
> public interface AbstractBitSet 
> {
>   public boolean get(int index);
> }
> {code}
> It would be useful if the method =Filter.bits()= returned an abstract 
interface, instead of =java.util.BitSet=.
> Use case: there is a very large index, and, depending on the user's 
privileges, only a small portion of the index is actually visible.
> Sparsely populated =java.util.BitSet=s are not efficient and waste lots of 
memory. It would be desirable to have an alternative BitSet implementation 
with smaller memory footprint.
> Though it _is_ possibly to derive classes from =java.util.BitSet=, it was 
obviously not designed for that purpose.
> That's why I propose to use an interface instead. The default implementation 
could still delegate to =java.util.BitSet=.

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