Understanding and configuring freshness boost

Symptom

The boost-tables section of the index-profile and its interaction with freshness is unclear:

<freshness-boost time-offset="1"
                default-boost="17"
                boost-coefficient="40">
  <boost-table-entries>32 31 30 29 28 27
      26 25 24 23 22 21 20 19 18 17 16 15
      14 13 12 11 10 9 8 7 6 5 4 3 2 1
  </boost-table-entries>
</freshness-boost>

Cause

The product guide does not go into detail regarding the default settings in the boost-table entries or their use in the calculation of freshness.  

Resolution

The boost table entries are values into which the base 2 logarithm of the time difference is used as an index. For example, if the current time in the default datatime resolution of "minutes" was 3694714440 and a sample document had a time of 3694714369, which is 71 minutes before that. Log_2(71) is approximately 6, and the table values are mapped from ranges as follows:

1: <2
2: 2-3
3: 4-7

And so forth. For this example, the table entry to use would be the 3rd one, or 30. This is then multiplied by the boost coefficient (40), resulting in a freshness boost of of 1200 for the example document - the final boost may be lower, depending on the weight given to freshness in the rank profile.

More Information

The boost table can be customized to create a different "scale" of freshness.
Propiedades

Id. de artículo: 2288566 - Última revisión: 14-04-2011 - Revisión: 1

FAST ESP 5.3, FAST ESP

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