Wonderful! That explains it. Thanks a lot! Regards,
On Mon, Mar 8, 2010 at 6:39 AM, Jay Hill <jayallenh...@gmail.com> wrote: > Yes, if omitNorms=true, then no lengthNorm calculation will be done, and > the > fieldNorm value will be 1.0, and lengths of the field in question will not > be a factor in the score. > > To see an example of this you can do a quick test. Add two "text" fields, > and on one omitNorms: > > <field name="foo" type="text" indexed="true" stored="true"/> > <field name="bar" type="text" indexed="true" stored="true" > omitNorms="true"/> > > Index a doc with the same value for both fields: > <field name="foo">1 2 3 4 5</field> > <field name="bar">1 2 3 4 5</field> > > Set &debugQuery=true and do two queries: &q=foo:5 &q=bar:5 > > in the "explain" section of the debug output note that the fieldNorm value > for the "foo" query is this: > > 0.4375 = fieldNorm(field=foo, doc=1) > > and the value for the "bar" query is this: > > 1.0 = fieldNorm(field=bar, doc=1) > > A simplified description of how the fieldNorm value is: fieldNorm = > lengthNorm * documentBoost * documentFieldBoosts > > and the lengthNorm is calculated like this: lengthNorm = > 1/(numTermsInField)**.5 > [note that the value is encoded as a single byte, so there is some > precision > loss] > > When omitNorms=true no norm calculation is done, so fieldNorm will always > be > one on those fields. > > You can also use the Luke utility to view the document in the index, and it > will show that there is a norm value for the foo field, but not the bar > field. > > -Jay > http://www.lucidimagination.com > > > On Sun, Mar 7, 2010 at 5:55 AM, Siddhant Goel <siddhantg...@gmail.com > >wrote: > > > Hi everyone, > > > > Is the fieldNorm calculation altered by the omitNorms factor? I saw on > this > > page (http://old.nabble.com/Question-about-fieldNorm-td17782701.html) > the > > formula for calculation of fieldNorms (fieldNorm = > > fieldBoost/sqrt(numTermsForField)). > > > > Does this mean that for a document containing a string like "A B C D E" > in > > its field, its fieldNorm would be boost/sqrt(5), and for another document > > containing the string "A B C" in the same field, its fieldNorm would be > > boost/sqrt(3). Is that correct? > > > > If yes, then is *this* what omitNorms affects? > > > > Thanks, > > > > -- > > - Siddhant > > > -- - Siddhant
