lucene-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Michael McCandless <luc...@mikemccandless.com>
Subject Re: Empty Sink Tokenizer
Date Tue, 31 Mar 2009 18:38:52 GMT
There are two separate things, here.

First is that indexed fields are now processed in alpha order
(stable/partial sort for multivalued fields), as of 2.3.  That I think
is something internal to Lucene and I'm not sure we should make
promises one way or another in what order Lucene visits the fields on
a document (maybe someday multiple threads will run on fields... who
knows).

This I think was the original problem reported on java-user, because
Lucene tried to pull tokens from the sink before it was filled.

I'm not sure how best to fix Sink/TeeTokenizer to "be flexible".
Maybe we could change it so that whichever TokenStream is pulled
first, it then pulls from the true source and populates the other as a
sink.  Then when the other is used, it's always populated.

So a TeeTokenFilter would take a single source and export two copies
(TokenFilters) and you'd use those copies in your fields.

The second issue is that when you store fields in a document and
retrieve the document later, the fields have been sorted by name.  I
think this is basically another case of "the document you provided
during indexing isn't the same thing as what you retrieve at search
time" (as Yonik said).

I'm also not sure we should promise it (though, reverting to the
pre-2.3 approach is possible, and easier than changing order that we
invert fields), or maybe we should wait until we work out input vs
output documents.  And, apparently not many people have noticed this
2nd issue...

Mike

On Tue, Mar 31, 2009 at 12:26 PM, Grant Ingersoll <gsingers@apache.org> wrote:
> Well, we don't make any guarantees about it in docs, AFAICT, but we have in
> the past advertised it (via the mailing lists) as such.  The Tee/Sink stuff
> does rely on what has been the de facto way of doing things up until 2.3 it
> sounds.  The snippet of code I included can easily be converted to a test
> case if we wish to enforce it going forward.
>
> What's the benefit of collation?  I don't know if this is considered a
> back-compatible breakage or not (likely not) but this issue does come up
> from time to time and there are people that have relied on our answer.
>
> In the end, we should document whichever it is going to be and then make
> sure the Tee/Sink stuff documents it as well.
>
>
>
> On Mar 31, 2009, at 10:51 AM, Michael McCandless wrote:
>
>> Uh-oh: I think this happened as part of LUCENE-843, which landed in 2.3.
>>
>> IndexWriter now first collates each Field instance, by name, and then
>> visits those fields in sorted order.  Multiple instances of the same
>> field name are written in the order that they appeared in the
>> document.
>>
>> StoredFieldsWriter taps in to the indexing chain after that per-field
>> collation.
>>
>> But, if getting back to this is important, we should be able to move
>> StoredFieldsWriter up in the chain so that it visits the original
>> document, instead.  Offhand, I'm not sure if there are any tradeoffs
>> in doing that.
>>
>> Mike
>>
>> On Tue, Mar 31, 2009 at 9:30 AM, Grant Ingersoll <gsingers@apache.org>
>> wrote:
>>>
>>> Has the way fields get added changed recently?
>>>
>>>  http://www.lucidimagination.com/search/document/954555c478002a3/empty_sinktokenizer
>>>
>>> See also:
>>>
>>> http://www.lucidimagination.com/search/document/274ec8c1c56fdd54/order_of_field_objects_within_document#5ffce4509ed32511
>>>
>>>
>>> http://www.lucidimagination.com/search/document/d6b19ab1bd87e30a/order_of_fields_returned_by_document_getfields#d6b19ab1bd87e30a
>>>
>>>
>>> http://www.lucidimagination.com/search/document/deda4dd3f9041bee/the_order_of_fields_in_document_fields#bb26d84091aebcaa
>>>
>>>
>>> The following little program confirms that they are indeed in alpha order
>>> now and not in added order:
>>> public class TestFieldOrdering extends LuceneTestCase {
>>>  protected RAMDirectory dir;
>>>
>>>  protected void setUp() throws Exception {
>>>   super.setUp();
>>>   dir = new RAMDirectory();
>>>
>>>  }
>>>
>>>  public void testAddFields() throws Exception {
>>>   IndexWriter writer = new IndexWriter(dir, new SimpleAnalyzer(), true,
>>> IndexWriter.MaxFieldLength.LIMITED);
>>>
>>>   Document doc = new Document();
>>>   doc.add(new Field("id", "one", Field.Store.YES, Field.Index.NO));
>>>   doc.add(new Field("z", "document z", Field.Store.YES,
>>> Field.Index.ANALYZED));
>>>   doc.add(new Field("a", "document a", Field.Store.YES,
>>> Field.Index.ANALYZED));
>>>   doc.add(new Field("e", "document e", Field.Store.YES,
>>> Field.Index.ANALYZED));
>>>   doc.add(new Field("b", "document b", Field.Store.YES,
>>> Field.Index.ANALYZED));
>>>   writer.addDocument(doc);
>>>   writer.close();
>>>   IndexReader reader = IndexReader.open(dir);
>>>   Document retreived = reader.document(0);
>>>   assertTrue("retreived is null and it shouldn't be", retreived != null);
>>>   List fields = retreived.getFields();
>>>   for (Iterator iterator = fields.iterator(); iterator.hasNext();) {
>>>     Field name = (Field) iterator.next();
>>>     System.out.println("Name: " + name);
>>>   }
>>>  }
>>>
>>> }
>>>
>>> ---------------------------------------------------------------------
>>> To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
>>> For additional commands, e-mail: java-dev-help@lucene.apache.org
>>>
>>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
>> For additional commands, e-mail: java-dev-help@lucene.apache.org
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
> For additional commands, e-mail: java-dev-help@lucene.apache.org
>
>

---------------------------------------------------------------------
To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: java-dev-help@lucene.apache.org


Mime
View raw message