FAQ
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);
}

to:

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

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

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


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

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.


Regards,
Paul Elschot








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

Subject: [jira] Commented: (LUCENE-584) Decouple Filter from BitSet
Date: Friday 10 August 2007 01:15
From: "Mark Harwood (JIRA)" <jira@apache.org>
To: java-dev@lucene.apache.org



[ https://issues.apache.org/jira/browse/LUCENE-584?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12518868 ]

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.

Cheers
Mark
Decouple Filter from BitSet
---------------------------

Key: LUCENE-584
URL: https://issues.apache.org/jira/browse/LUCENE-584
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,
Some Matchers.zip

{code}
package org.apache.lucene.search;
public abstract class Filter implements java.io.Serializable
{
public abstract AbstractBitSet bits(IndexReader reader) throws
IOException;
}
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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