Hi,
Is there a working example for this? Is this mentioned in the Lucene
Javadocs or any other docs so that i can look it?
To index the docvalues, see NumericDocValuesField (it can be added to documents
like indexed or stored fields). You may have used them for sorting already.
this methodology seems sort of like discouraging using index time boosting.
Not really. Many use this all the time. It's one of the killer features of both
Solr and Elasticsearch. The problem was how the Document.setBoost()worked (it
did not work correctly, see below).
Previous setBoost method call was fine and easy to use.
Did it have some performance issues and then is that why it was deprecated?
No the reason for deprecating this was for several reasons: setBoost was not
doing what the user had expected. Internally the boost value was just
multiplied into the document norm factor (which is internally also a docvalues
field). The norm factors are only very inprecise floats stored in a byte, so
precision is not well. If you put some values into it and the length norm was
already consuming all bits, the boosting was very coarse. It was also only
multiplied into and most users want to do some stuff like record click counts
in the index and then boost for example with the logarithm or some other
function. If the boost is just multiplied into the length norm you have no
flexibility at all.
In addition you can have several docvalues fields and use their values in a
function (e.g. one field with click count and another one with product price).
After that you can combine click count and price (which can be modified
indipenently during index updates) and change boost to boost lower price and
higher click count up.
This is what you can do with the expressions module. You just give it a
function.
Here is an example, the second example is using a FunctionScoreQuery that
modifies the score based on the function and the given docvalues:
https://urldefense.proofpoint.com/v2/url?u=https-3A__lucene.apache.org_core_7-5F7-5F2_expressions_org_apache_lucene_expressions_Expression.html&d=DwIFaQ&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=nlG5z5NcNdIbQAiX-BKNeyLlULCbaezrgocEvPhQkl4&m=6m6i5zZXPZNP6DyVv_xG4vXnVTPEdfKLeLSvGjEXbyw&s=B5_kGwRIbAoGqL0-SVR9r3t78E5XUuzLT37TeyV-bv8&e=
FunctionScoreQuery usage with MultiFieldQueryParser would also be nice
where
MultiFieldQuery already has boosts field to do this in its constructor.
The boots in the query parser are applied for fields during query time (to have
a different weight per field). Index time boosting is per document. So you can
combine both.
Maybe it is not needed with MultiFieldQueryParser.
You use MultiFieldQueryParser to adjust weights of the fields (e.g. title
versus body). The parsed query is then wrapped with an expression that modifies
the score per document according to the docvalues.
Uwe
On 10/18/19 1:28 PM, Uwe Schindler wrote:
Hi,
that's not true. You can do index time boosting, but you need to do that
using a separate field. You just index a numeric docvalues field (which may
contain a long or float value per document). Later you wrap your query with
some FunctionScoreQuery (e.g., use the Javascript function query syntax in
the expressions module). This allows you to compile a javascript function
that calculated the final score based on the score returned by the inner query
and combines them with docvalues that were indexed per document.
Uwe
-----
Uwe Schindler
Achterdiek 19, D-28357 Bremen
https://urldefense.proofpoint.com/v2/url?u=https-
3A__www.thetaphi.de&d=DwIFaQ&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIr
MUB65eapI_JnE&r=nlG5z5NcNdIbQAiX-
BKNeyLlULCbaezrgocEvPhQkl4&m=6rVk8db2H8dAcjS3WCWmAPd08C7JQCvZ
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eMail: u...@thetaphi.de
-----Original Message-----
From: baris.ka...@oracle.com <baris.ka...@oracle.com>
Sent: Friday, October 18, 2019 5:28 PM
To: java-user@lucene.apache.org
Cc: baris.ka...@oracle.com
Subject: Re: Index-time boosting: Deprecated setBoost method
It looks like index-time boosting (field) is not possible since Lucene
version 7.7.2 and
i was using before for another case the BoostQuery at search time for
boosting and
this seems to be the only boosting option now in Lucene.
Best regards
On 10/18/19 10:01 AM, baris.ka...@oracle.com wrote:
Hi,-
i saw this in the Field class docs and i am figuring out the following
note in the docs:
setBoost(float boost)
Deprecated.
Index-time boosts are deprecated, please index index-time scoring
factors into a doc value field and combine them with the score at
query time using eg. FunctionScoreQuery.
I appreciate this note. Is there an example about this? I wish docs
would give a simple example to further help.
https://urldefense.proofpoint.com/v2/url?u=https-
3A__lucene.apache.org_core_6-5F6-
5F0__core_org_apache_lucene_document_&d=DwIFaQ&c=RoP1YumCXCga
WHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=nlG5z5NcNdIbQAiX-
BKNeyLlULCbaezrgocEvPhQkl4&m=6rVk8db2H8dAcjS3WCWmAPd08C7JQCvZ
8W80yE9L5xY&s=rIVbw3_TGEwpaet5ibCeYze6vSDUiPhwOzlV0z484fM&e=
Field.html
vs
https://urldefense.proofpoint.com/v2/url?u=https-
3A__lucene.apache.org_core_7-5F7-
5F2_core_org_apache_lucene_document_F&d=DwIFaQ&c=RoP1YumCXCgaW
HvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=nlG5z5NcNdIbQAiX-
BKNeyLlULCbaezrgocEvPhQkl4&m=6rVk8db2H8dAcjS3WCWmAPd08C7JQCvZ
8W80yE9L5xY&s=yt1toHHZQBqd3qKpWeSzywGJhy928Q5qaEO4v9Lj3vg&e=
ield.html
Best regards
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