I thought of a possible enhancement - before I go down the road, I am
looking for some input form the community?
Currently, the QueryFilter caches the bits base upon the IndexReader.
The problem with this is small incremental changes to the index
invalidate the cache.
What if instead the filter determined that the underlying IndexReader
was a MultiReader and then maintained a bitset for each reader,
combining them in bits() when requested. The filter could check if
any of the underlying readers were the different (removed or added)
and then just create a new bitset for that reader. With the new non-
bit set filter implementations this could be even more memory
efficient since the bitsets would not need to be combined into a
single bitset.
With the previous work on "reopen" so that segments are reused, this
would allow filters to be far more useful in a highly interactive
environment.
What do you think?
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I'm no segments/MultiReader expert, but your idea sounds good to me it
seems like it would certainly work in the "new segments" situation.

thing i don't see you mention is dealing with deletions i'm not
sure if deleting documents cause the version number of an IndexReader to
change or not (if it does your job is easy) but even if it doesn't I'm
guessing you could say that if hasDeletions() returns true, you have to
assume you need to invalidate your cached bits (worst case scenerio you
are invalidating the cache as often as it is now)

: Date: Fri, 7 Jul 2006 00:32:54 -0500
: From: robert engels <rengels (AT) ix (DOT) netcom.com>
: Reply-To: java-dev (AT) lucene (DOT) apache.org
: To: Lucene-Dev <java-dev (AT) lucene (DOT) apache.org>
: Subject: MultiSegmentQueryFilter enhancement for interactive indexes?
:
: I thought of a possible enhancement - before I go down the road, I am
: looking for some input form the community?
:
: Currently, the QueryFilter caches the bits base upon the IndexReader.
:
: The problem with this is small incremental changes to the index
: invalidate the cache.
:
: What if instead the filter determined that the underlying IndexReader
: was a MultiReader and then maintained a bitset for each reader,
: combining them in bits() when requested. The filter could check if
: any of the underlying readers were the different (removed or added)
: and then just create a new bitset for that reader. With the new non-
: bit set filter implementations this could be even more memory
: efficient since the bitsets would not need to be combined into a
: single bitset.
:
: With the previous work on "reopen" so that segments are reused, this
: would allow filters to be far more useful in a highly interactive
: environment.
:
: What do you think?
:
:
:
:
:
:
:
: To unsubscribe, e-mail: java-dev-unsubscribe (AT) lucene (DOT) apache.org
: For additional commands, e-mail: java-dev-help (AT) lucene (DOT) apache.org
:

-Hoss

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7/7/06, robert engels <rengels (AT) ix (DOT) netcom.comwrote:
Exactly. I have been watching to see how the new filer interface
works out for 2.0. I am still not certain why it is so involved.

I still think

interface Filter {
boolean include(int doc);
int nextInclude(int doc);
}

should suffice.

It depends on how the interface will be used and the capabilities of
the underlying implementation.
Paul's sorted vint list is good on space, but it doesn't do random access well.
Solr's HashDocSet offers very fast random access, but it doesn't do
sequential access.
A BitSet does both, but it's always big.
There are many other possible implementations & tradeoffs, but you get
the idea
-Yonik
Solr, the open-source Lucene search server

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This might be even better in conjunction with moving away from BitSet
to some sort of interface like DocNrSkipper that way you would
never have to combine the filters into a single BitSet.

-Yonik
Solr, the open-source Lucene search server

7/7/06, robert engels <rengels (AT) ix (DOT) netcom.comwrote:
I implemented it and it works great. I didn't worry about the
deletions since by the time a filter is used the deleted documents
are already removed by the query. The only problem that arose out of
this was for things like the ConstantScoreQuery (which uses a filter)
- I needed to modify this query to ignore deleted documents.

Now I have incremental cached filters - the query performance is
going through the roof.
>
>
>
Jul 7, 2006, at 2:47 PM, Chris Hostetter wrote:
--
I'm no segments/MultiReader expert, but your idea sounds good to
me it
seems like it would certainly work in the "new segments" situation.

thing i don't see you mention is dealing with deletions i'm
not
sure if deleting documents cause the version number of an
IndexReader to
change or not (if it does your job is easy) but even if it doesn't I'm
guessing you could say that if hasDeletions() returns true, you
have to
assume you need to invalidate your cached bits (worst case scenerio
you
are invalidating the cache as often as it is now)
--
: Date: Fri, 7 Jul 2006 00:32:54 -0500
: From: robert engels <rengels (AT) ix (DOT) netcom.com>
: Reply-To: java-dev (AT) lucene (DOT) apache.org
: To: Lucene-Dev <java-dev (AT) lucene (DOT) apache.org>
: Subject: MultiSegmentQueryFilter enhancement for interactive
indexes?
:
: I thought of a possible enhancement - before I go down the road,
I am
: looking for some input form the community?
:
: Currently, the QueryFilter caches the bits base upon the
IndexReader.
:
: The problem with this is small incremental changes to the index
: invalidate the cache.
:
: What if instead the filter determined that the underlying
IndexReader
: was a MultiReader and then maintained a bitset for each reader,
: combining them in bits() when requested. The filter could check if
: any of the underlying readers were the different (removed or added)
: and then just create a new bitset for that reader. With the new non-
: bit set filter implementations this could be even more memory
: efficient since the bitsets would not need to be combined into a
: single bitset.
:
: With the previous work on "reopen" so that segments are reused, this
: would allow filters to be far more useful in a highly interactive
: environment.
:
: What do you think?

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For additional commands, e-mail: java-dev-help (AT) lucene (DOT) apache.org

Exactly. I have been watching to see how the new filer interface
works out for 2.0. I am still not certain why it is so involved.

I still think

interface Filter {
boolean include(int doc);
int nextInclude(int doc);
}

should suffice.

Jul 7, 2006, at 9:53 PM, Yonik Seeley wrote:

This might be even better in conjunction with moving away from BitSet
to some sort of interface like DocNrSkipper that way you would
never have to combine the filters into a single BitSet.
--
-Yonik
Solr, the open-source Lucene
search server

7/7/06, robert engels <rengels (AT) ix (DOT) netcom.comwrote:
>I implemented it and it works great. I didn't worry about the
>deletions since by the time a filter is used the deleted documents
>are already removed by the query. The only problem that arose out of
>this was for things like the ConstantScoreQuery (which uses a filter)
>- I needed to modify this query to ignore deleted documents.
>>
>Now I have incremental cached filters - the query performance is
>going through the roof.
>>
>>
>>
>Jul 7, 2006, at 2:47 PM, Chris Hostetter wrote:
>>
>>
>I'm no segments/MultiReader expert, but your idea sounds good to
>me it
>seems like it would certainly work in the "new segments" situation.
>>
>thing i don't see you mention is dealing with deletions i'm
>not
>sure if deleting documents cause the version number of an
>IndexReader to
>change or not (if it does your job is easy) but even if it
>doesn't I'm
>guessing you could say that if hasDeletions() returns true, you
>have to
>assume you need to invalidate your cached bits (worst case scenerio
>you
>are invalidating the cache as often as it is now)
>>
>>
>: Date: Fri, 7 Jul 2006 00:32:54 -0500
>: From: robert engels <rengels (AT) ix (DOT) netcom.com>
>: Reply-To: java-dev (AT) lucene (DOT) apache.org
>: To: Lucene-Dev <java-dev (AT) lucene (DOT) apache.org>
>: Subject: MultiSegmentQueryFilter enhancement for interactive
>indexes?
>:
>: I thought of a possible enhancement - before I go down the road,
>I am
>: looking for some input form the community?
>:
>: Currently, the QueryFilter caches the bits base upon the
>IndexReader.
>:
>: The problem with this is small incremental changes to the index
>: invalidate the cache.
>:
>: What if instead the filter determined that the underlying
>IndexReader
>: was a MultiReader and then maintained a bitset for each reader,
>: combining them in bits() when requested. The filter could
>check if
>: any of the underlying readers were the different (removed or
>added)
>: and then just create a new bitset for that reader. With the
>new non-
>: bit set filter implementations this could be even more memory
>: efficient since the bitsets would not need to be combined into a
>: single bitset.
>:
>: With the previous work on "reopen" so that segments are
>reused, this
>: would allow filters to be far more useful in a highly interactive
>: environment.
>:
>: What do you think?
>

To unsubscribe, e-mail: java-dev-unsubscribe (AT) lucene (DOT) apache.org
For additional commands, e-mail: java-dev-help (AT) lucene (DOT) apache.org

To unsubscribe, e-mail: java-dev-unsubscribe (AT) lucene (DOT) apache.org
For additional commands, e-mail: java-dev-help (AT) lucene (DOT) apache.org

I implemented it and it works great. I didn't worry about the
deletions since by the time a filter is used the deleted documents
are already removed by the query. The only problem that arose out of
this was for things like the ConstantScoreQuery (which uses a filter)
- I needed to modify this query to ignore deleted documents.

Now I have incremental cached filters - the query performance is
going through the roof.

Jul 7, 2006, at 2:47 PM, Chris Hostetter wrote:

I'm no segments/MultiReader expert, but your idea sounds good to
me it
seems like it would certainly work in the "new segments" situation.

thing i don't see you mention is dealing with deletions i'm
not
sure if deleting documents cause the version number of an
IndexReader to
change or not (if it does your job is easy) but even if it doesn't I'm
guessing you could say that if hasDeletions() returns true, you
have to
assume you need to invalidate your cached bits (worst case scenerio
you
are invalidating the cache as often as it is now)
--
: Date: Fri, 7 Jul 2006 00:32:54 -0500
: From: robert engels <rengels (AT) ix (DOT) netcom.com>
: Reply-To: java-dev (AT) lucene (DOT) apache.org
: To: Lucene-Dev <java-dev (AT) lucene (DOT) apache.org>
: Subject: MultiSegmentQueryFilter enhancement for interactive
indexes?
:
: I thought of a possible enhancement - before I go down the road,
I am
: looking for some input form the community?
:
: Currently, the QueryFilter caches the bits base upon the
IndexReader.
:
: The problem with this is small incremental changes to the index
: invalidate the cache.
:
: What if instead the filter determined that the underlying
IndexReader
: was a MultiReader and then maintained a bitset for each reader,
: combining them in bits() when requested. The filter could check if
: any of the underlying readers were the different (removed or added)
: and then just create a new bitset for that reader. With the new non-
: bit set filter implementations this could be even more memory
: efficient since the bitsets would not need to be combined into a
: single bitset.
:
: With the previous work on "reopen" so that segments are reused, this
: would allow filters to be far more useful in a highly interactive
: environment.
:
: What do you think?
:
:
:
:
:
:
:

: To unsubscribe, e-mail: java-dev-unsubscribe (AT) lucene (DOT) apache.org
: For additional commands, e-mail: java-dev-help (AT) lucene (DOT) apache.org
:
>
>
>
-Hoss
--

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Agreed. The interface I proposed supports both sequential and random
access to the filter - hiding the implementation.

Jul 7, 2006, at 10:10 PM, Yonik Seeley wrote:

7/7/06, robert engels <rengels (AT) ix (DOT) netcom.comwrote:
>Exactly. I have been watching to see how the new filer interface
>works out for 2.0. I am still not certain why it is so involved.
>>
>I still think
>>
>interface Filter {
>boolean include(int doc);
>int nextInclude(int doc);
>}
>>
>should suffice.
>
It depends on how the interface will be used and the capabilities of
the underlying implementation.
Paul's sorted vint list is good on space, but it doesn't do random
access well.
Solr's HashDocSet offers very fast random access, but it doesn't do
sequential access.
A BitSet does both, but it's always big.
There are many other possible implementations & tradeoffs, but you get
the idea

-Yonik
Solr, the open-source Lucene
search server

To unsubscribe, e-mail: java-dev-unsubscribe (AT) lucene (DOT) apache.org
For additional commands, e-mail: java-dev-help (AT) lucene (DOT) apache.org

To unsubscribe, e-mail: java-dev-unsubscribe (AT) lucene (DOT) apache.org
For additional commands, e-mail: java-dev-help (AT) lucene (DOT) apache.org

Saturday 08 July 2006 05:44, robert engels wrote:
Agreed. The interface I proposed supports both sequential and random
access to the filter - hiding the implementation.

For query searching, random access to a Filter is only needed
in the forward direction, e.g. by nextInclude(docNr) or skipTo(docNr).

As for why it's so involved:

Making a "rewritten" Filter work more like a Scorer has the advantage
that combinations of filters can (also) be evaluated using the same
mechanisms as currently existing for Scorers. For this, some additions
to the existing code will be needed, like adding an
add(Filter, BooleanC) to BooleanQuery, and a similar
addition of a Matcher (proposed superclass of Scorer to "rewrite" a
Filter to) to some of the underlying scorers.
Such occurrences of filters are only "must" and "must not", "should"
doesn't make sense because there is no score value.

Also, it makes sense to have an explain() method for a "rewritten"
Filter, because it can be for searching a query.

Regards,
Paul Elschot

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Attached is the incremental updating QueryFilter. The MyMultiReader
class is a basic extension of MultiReader that allows access to the
underlying IndexReaders.

this also requires that "reopen" be implemented so that
SegmentReaders for unchanged segments remain the same through the open.

Robert

Jul 8, 2006, at 7:14 AM, robert engels wrote:

Is that really necessary for a filter? It seems that a filter
implies efficiency over a "scoring", and that filters should be
able to be evaluated in a chained (or priority queue) fashion
fairly efficiently without any need for 'rewrites".

With the new incremental updates of a filter (based upon a query)
it seems that the newly proposed filtering could be far less
efficient.

I think a filter change that just removes the BitSet dependency is
all that is needed, and anything else is overkill, but I admit I am
probably missing something here.

If these changes will eventually allow for efficient filtering
based upon non-indexed stored fields I am all for it.

Jul 8, 2006, at 2:24 AM, Paul Elschot wrote:
>
>Saturday 08 July 2006 05:44, robert engels wrote:
Agreed. The interface I proposed supports both sequential and random
access to the filter - hiding the implementation.
>>
>For query searching, random access to a Filter is only needed
>in the forward direction, e.g. by nextInclude(docNr) or skipTo
>(docNr).
>>
>As for why it's so involved:
>>
>Making a "rewritten" Filter work more like a Scorer has the advantage
>that combinations of filters can (also) be evaluated using the same
>mechanisms as currently existing for Scorers. For this, some
>additions
>to the existing code will be needed, like adding an
>add(Filter, BooleanC) to BooleanQuery, and a similar
>addition of a Matcher (proposed superclass of Scorer to "rewrite" a
>Filter to) to some of the underlying scorers.
>Such occurrences of filters are only "must" and "must not", "should"
>doesn't make sense because there is no score value.
>>
>Also, it makes sense to have an explain() method for a "rewritten"
>Filter, because it can be for searching a query.
>>
>Regards,
>Paul Elschot
>>
>
>To unsubscribe, e-mail: java-dev-unsubscribe (AT) lucene (DOT) apache.org
>For additional commands, e-mail: java-dev-help (AT) lucene (DOT) apache.org
>>
>
>

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Is that really necessary for a filter? It seems that a filter implies
efficiency over a "scoring", and that filters should be able to be
evaluated in a chained (or priority queue) fashion fairly efficiently
without any need for 'rewrites".

With the new incremental updates of a filter (based upon a query) it
seems that the newly proposed filtering could be far less efficient.

I think a filter change that just removes the BitSet dependency is
all that is needed, and anything else is overkill, but I admit I am
probably missing something here.

If these changes will eventually allow for efficient filtering based
upon non-indexed stored fields I am all for it.

Jul 8, 2006, at 2:24 AM, Paul Elschot wrote:

Saturday 08 July 2006 05:44, robert engels wrote:
>Agreed. The interface I proposed supports both sequential and random
>access to the filter - hiding the implementation.
>
For query searching, random access to a Filter is only needed
in the forward direction, e.g. by nextInclude(docNr) or skipTo(docNr).

As for why it's so involved:

Making a "rewritten" Filter work more like a Scorer has the advantage
that combinations of filters can (also) be evaluated using the same
mechanisms as currently existing for Scorers. For this, some additions
to the existing code will be needed, like adding an
add(Filter, BooleanC) to BooleanQuery, and a similar
addition of a Matcher (proposed superclass of Scorer to "rewrite" a
Filter to) to some of the underlying scorers.
Such occurrences of filters are only "must" and "must not", "should"
doesn't make sense because there is no score value.

Also, it makes sense to have an explain() method for a "rewritten"
Filter, because it can be for searching a query.

Regards,
Paul Elschot

To unsubscribe, e-mail: java-dev-unsubscribe (AT) lucene (DOT) apache.org
For additional commands, e-mail: java-dev-help (AT) lucene (DOT) apache.org

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Robert,

Thanks for your questions, things are beginning to fall into place
(see ):

Saturday 08 July 2006 14:14, robert engels wrote:
Is that really necessary for a filter? It seems that a filter implies
efficiency over a "scoring", and that filters should be able to be

The proposed Matcher is superclass of Scorer formed by leaving
out all the methods dealing with score values.

evaluated in a chained (or priority queue) fashion fairly efficiently

The current DisjunctionSumScorer has a priority queue. I have to say
that I did not yet consider a filter clause to a boolean query that is
based on an disjunction of filters: in this case the "should" occurrence
makes sense, but calling it a query is overdoing it, the disjunction
would be a Filter itself.

In principle, it is possible to evaluate a disjunction over filters during a
query search, and it might even make sense when the disjunction is
skipTo'd into infrequently as one of the required clauses in a boolean query.
I have no idea whether this would be useful in practice.

Also, in the same way as for top level disjunction queries, for filters
there are more efficient methods of dealing with top level disjunction
than a priority queue, see for example RangeFilter that collects
all matching docs in a BitSet by iterating the TermScorers in the range
one by one.

The distinction between top level evaluation and nested evaluation is
in the proposed Matcher: it has a match(MatchCollector) method for the top
level, and the doc(), next() and skipTo() can be used for nested evaluation.
The same distinction exists in Scorer: score(HitCollector, ) and roughly
the rest.

without any need for 'rewrites".

Rewriting of a query is a way to make an association between
a query and one or more index readers. The same association is currently
present for a Filter in the bits(IndexReader) method, proposed
to be deprecated.
Perhaps the proposed getMatcher(IndexReader) method should
be called Filter.rewrite(IndexReader), just as Query.rewrite(IndexReader).

With the new incremental updates of a filter (based upon a query) it
seems that the newly proposed filtering could be far less efficient.

A Filter can be composed in the same way as an IndexReader can use
multiple segments. Also, document deletion in a segment is currently done
by a special purpose bit set.
For incremental updates, the "rewriting" of a filter could be limited to the
filter component associated with the newly added segment(s).

I think a filter change that just removes the BitSet dependency is
all that is needed, and anything else is overkill, but I admit I am

I thought so, too. But then I realized that there are many things shared
between current Scorers and Filters. These things are dealing mostly
with matching and not at all with scoring.

probably missing something here.

Perhaps a method to provide a complete Explanation of why a document
matches, or does not match, a filtered query?

If these changes will eventually allow for efficient filtering based
upon non-indexed stored fields I am all for it.

For the non indexed case, there is no choice but to read all stored data
and evaluate a boolean function on the field of each document.
I think the only efficiency to be gained there is in reading the stored
fields, but iirc that has been fixed.
For the indexed case a TermScorer is a Scorer is a proposed Matcher.
The norms can already be left out, so the only things "left to be left out"
are the term frequencies and positions. that is done there is no
more need to use a non-indexed stored field for filtering, because an
indexed-only field would always be more efficient in indexed data size.

Regards,
Paul Elschot

Jul 8, 2006, at 2:24 AM, Paul Elschot wrote:

Saturday 08 July 2006 05:44, robert engels wrote:
>Agreed. The interface I proposed supports both sequential and random
>access to the filter - hiding the implementation.
>
For query searching, random access to a Filter is only needed
in the forward direction, e.g. by nextInclude(docNr) or skipTo(docNr).

As for why it's so involved:

Making a "rewritten" Filter work more like a Scorer has the advantage
that combinations of filters can (also) be evaluated using the same
mechanisms as currently existing for Scorers. For this, some additions
to the existing code will be needed, like adding an
add(Filter, BooleanC) to BooleanQuery, and a similar
addition of a Matcher (proposed superclass of Scorer to "rewrite" a
Filter to) to some of the underlying scorers.
Such occurrences of filters are only "must" and "must not", "should"
doesn't make sense because there is no score value.

Also, it makes sense to have an explain() method for a "rewritten"
Filter, because it can be for searching a query.

Regards,
Paul Elschot

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