Stronger boosting by date in Solr

Question

Boosting by date field in solr is defined as:

{!boost b=recip(ms(NOW,datefield),3.16e-11,1,1)}

I looked everywhere (examples: Solr Dismax C

Answer 1

There is an example very well presented in the ReciprocalFloatFunction that will give you a clear view on how the boosting recipe works. If you find that dismax does not offer you enough control over the boosting, you will have to do some tinkering with BoostQParserPlugin.

A multiplier of 3.16e-11 changes the units from milliseconds to years (since there are about 3.16e10 milliseconds per year). Thus, a very recent date will yield a value close to 1/(0+1) or 1, a date a year in the past will get a multiplier of about 1/(1+1) or 1/2, and date two years old will yield 1/(2+1) or 1/3.