Create Aggregations for Facets

All facet types allow you to calculate aggregations for each value of the facet.

See Also
About facets

You can define an aggregation by:

  • A virtual field expression defining the value to use for each hit.

  • A function to create the aggregated value.

For example, if you have a facet based on the "country" of a sale, you can add an aggregation, on the price * quantity expression, using the "SUM" aggregation function. For each country, you get the total revenue generated by the sales on this country.

Table 1. Available Aggregation Functions for Facets

Function

Description

MIN

The minimum value of the expression for all documents in the facet value.

MAX

The maximum value the expression for all documents in the facet value.

SUM

The total of all values of the expression over all documents in the facet value.

AVG

The average value of the expression over all documents in the facet value.

STDDEV

The standard deviation of all values of the expression for all documents in the facet value.

CENTILE(x)

Computes Nth percentile of the expression for all documents in the facet value, where N is a double between 0.0 and 100.0.

COUNT

The count of all documents that contain a value for the expression set in the facet value.

Note: Do not confuse it with the category document count.

MAXDATE

Computes the max date based on index time. You can specify output format in a custom expression using date formats (see Which Facet Type Should I Use?).

MINDATE

Computes the min date based on index time. You can specify output format in a custom expression using date formats (see Which Facet Type Should I Use?).

Most Mashup UI widgets that display facets can use aggregations, instead of the simple count of the facet value.

The results of aggregation functions on NULL values in the Search API follows these conventions:

  • max(empty) = empty (that is, no value)

  • avg(empty) = empty (that is, no value)

  • sum(empty) = empty (that is, no value)

These values are returned as follows in the Access API (no values for unvalued aggregations): 

<exa:facet id="Language" path="Top/language" data="" description="Language" count="2" 
refinable="true" refinementPolicy="exclusive" type="category" nbClippedCategories="0" totalClippedCategories="0">
  <exa:facetInfo key="sort" value="count"/>
  <exa:facetInfo key="reverse" value="false"/>
  <exa:facetInfo key="hasRefine" value="false"/>
  <exa:aggregation id="mini" type="LONG"/>
  <exa:aggregation id="moyen" type="LONG"/>
  <exa:aggregation id="maxi" type="LONG"/>
  <exa:category id="f/Language/fr" path="Top/language/fr" data="" description="fr" count="2" score="0" 
state="DISPLAYED" nbClippedChildren="0">
    <exa:aggregation id="mini" type="LONG"/>
    <exa:aggregation id="moyen" type="LONG"/>
    <exa:aggregation id="maxi" type="LONG"/>
  </exa:category>
</exa:facet>