Field collapsing

This sub-tab allows for setting the collapsing rules for each field. The objective of the collapsing is to group identical results together to prevent interminable list of results.

Select the field(s) for which consecutive identical results are to be collapsed, and set the maximum number of consecutive result - if there are more consecutive results than allowed result, the extra results will be collapsed.

The most common field to be used for collapsing purposes is the standard OSS field 'host'.

Simple example of collapsing: a given field returns the following values:

A
A
A
A
A
B
A
B
B
B
B
C

If this field gets collapsed, with a max consecutive documents value set a 2, the results are:

A
A (collapsing was performed, there are three more results)
B
A
B
B (collapsing was performed, there are two more results)
C 

The two kinds of collapsing available in Open Search Server are :

• Optimised. The collapsing algorithm is only applied to the results being currently displayed. This consumes fewer resources up front.
• Full. The collapsing algorithm is applied to the whole list of results. This consumes more resource, but will provide a shorter list of results since everything will be pre-collapsed.