KSx::Index::LongFieldSUser)Contributed Perl DocumenKSx::Index::LongFieldSim(3)NAMEKSx::Index::LongFieldSim - Similarity optimized for long fields.
SYNOPSIS
package MySchema::body;
use base qw( KinoSearch::Plan::FullTextType );
use KSx::Index::LongFieldSim;
sub make_similarity { KSx::Index::LongFieldSim->new }
DESCRIPTION
KinoSearch's default Similarity implmentation produces a bias towards
extremely short fields.
KinoSearch::Index::Similarity
| more weight
| *
| **
| ***
| **********
| ********************
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| less weight ****
|------------------------------------------------------------------------
fewer tokens more tokens
LongFieldSim eliminates this bias.
KSx::Index::LongFieldSim
| more weight
|
|
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|*****************
| ********************
| *******************************
| less weight ****
|------------------------------------------------------------------------
fewer tokens more tokens
In most cases, the default bias towards short fields is desirable. For
instance, say you have two documents:
· "George Washington"
· "George Washington Carver"
If a user searches for "george washington", we want the exact title
match to appear first. Under the default Similarity implementation it
will, because the "Carver" in "George Washington Carver" dilutes the
impact of the other two tokens.
However, under LongFieldSim, the two titles will yield equal scores.
That would be bad in this particular case, but it could be good in
another.
"George Washington Carver is cool."
"George Washington Carver was born on the eve of the US Civil War, in
1864. His exact date of birth is unknown... Carver's research in crop
rotation revolutionized agriculture..."
The first document is succinct, but useless. Unfortunately, the
default similarity will assess it as extremely relevant to a query of
"george washington carver". However, under LongFieldSim, the short-
field bias is eliminated, and the addition of other mentions of
Carver's name in the second document yield a higher score and a higher
rank.
COPYRIGHT AND LICENSE
Copyright 2005-2010 Marvin Humphrey
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
perl v5.14.1 2011-06-20 KSx::Index::LongFieldSim(3)
