Performance tips on searching

Why not use a MultiSearcher an all single searchers? Or a Searcher on a
MultiReader consisting of all IndexReaders? With that you do not need to
merge the results.

By the way: instead of creating a TopDocCollector, you could also call
directly,

Searcher.search(Query query, Filter filter, int n, Sort sort)
Searcher.search(Query query, Filter filter, int n)

Filter can be null.

It's shorter and if sorting is also involved, simplier to handle (you do not
need to switch between ToDocCollector and TopFieldDocCollector).

Important: With Lucene 2.9, the searches will be faster using this API
(because then each index segment uses an own collector).

Uwe


-----
Uwe Schindler
H.-H.-Meier-Allee 63, D-28213 Bremen
http://www.thetaphi.de
eMail: [email protected]


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Hi

How do you expose a pagination without a customized hit collector. The
multi searcher does not expose a method for hit collector and sort.
Maybe this is not an issue for people ...

Cheers

Amin
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No, the MultiSearcher also exposes all methods, IndexSearcher/Seracher
exposes (it inherits it from the superclass IndexSearcher). And a call to
the collector is never sortable, because the sorting is done *inside* the
hit collector.

Where is your problem with pagination? Normally you choose n to be
paginationoffset+count and then display Scoredocs between n .. n+count-1.
There is no TopDocCollector that can only collect results 100 to 109. To
display results 100 to 109, you need to collect all results up to 109, so
call with n=110 and then display scoredoc[100]..scoredoc[109]

This is exactly how the old Hits worked.

-----
Uwe Schindler
H.-H.-Meier-Allee 63, D-28213 Bremen
http://www.thetaphi.de
eMail: [email protected]



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Hi

I wrote last week about the best way to paginate. I will reply back
with that email if that ok. This isn't my thread and I don't want to
deviate from the original topic.


Cheers

Amin
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Sorry I did not read your email and the first one a lot of people did not
understand (I read it now).

Everything is rather simple:
It makes no difference between MultiSearcher or IndexSearcher, you can
really do everything with both. Just use them as if they are equals (in your
declararation just use the abstract Searcher as you have done and assign a
MultiSearcher ord IndexSearcher to it).

Another possibility is to use only MultiReader on top of the IndexReaders
and create an IndexSearcher from this *one* MultiReader (which appears to
Lucene as a single index).

For the pagination, do it like described before.

I modified your code:

IndexSearcher searcher = searchers.get(indexName);
QueryParser parser = new QueryParser(indexName, analyzer);
TopDocs topDocs=null;
try {
topDocs = searcher.search(parser.parse(query), null, 10);
}
catch (ParseException e) {
}
Results results = new Results();
TopDocs topDocs = collector.topDocs();
ScoreDoc docs[] = topDocs.scoreDocs;
float maxScore = topDocs.getMaxScore();
for (int i = 0; i < docs.length; i++) {
Result result = new Result();
result.score = docs[i].score / maxScore;
result.doc = searcher.doc(docs[i].doc);
results.results.add(result);
}
return results;

For the pagination just use the following to display results 20 to 29 (10
items):

topDocs = searcher.search(parser.parse(query), null, 20+10);
ScoreDoc docs[] = topDocs.scoreDocs;
float maxScore = topDocs.getMaxScore();
for (int i = 20; i < 30; i++) {
result.score = docs[i].score / maxScore;
...

All complete, do the search on a single Searcher that contains all indexes
(a MultiSearcher(IndexReader(index1),IndexReader(index2),....) or a
IndexSearcher(MultiReader(index1,index2...)) and paginate as you want. If
you need sorting, just use a Sort/SortField construct and pass it to
Searcher.search().

Uwe
-----
Uwe Schindler
H.-H.-Meier-Allee 63, D-28213 Bremen
http://www.thetaphi.de
eMail: [email protected]



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