MarkLogic 10 Product Documentation

FacetDefinition.reduce

FacetDefinition.reduce(
   reducer as function,
   seed as anyValue
) as FacetDefinition

Summary

Specifies a function similar to Array.prototype.reduce() to apply to each value within the slice or a configuration object for the built-in reducer, as in a ValuesSearch definition.

Parameters
reducer	The reducing function.
seed	The initial reduction passed to the reducing function.

Usage Notes

You can pass in either a configuration object for the built-in reducer or a function reference to a custom reducer. The built-in reducer configuration object can have the following properties:

frequency

One of the string values "fragment", "item", or "none" (default). This setting controls whether or not to include the number of occurrences of each value. Fragment frequency is the number of fragments (documents) containing each value. Item frequency is the number occurrences of each value. Defaults to none.

When returning frequencies, the built-in reducer returns an object with the serialized value (or bucket name when using groupInto) as the key and the frequency as the value.

The reducer function should have the following signature:

function (prev, current, index, state)

Where the parameters have the following contents:

prev

The value returned by the previous call, or the seed value on the first call.

current

The current value.

index

The number of the current value.

state

A state object with a boolean-valued isLast> property that indicated the last call. You can set it to true to prematurely halt the reduction.

The return from the last call becomes the final reduced result.

You cannot use this method in conjunction with FacetDefinition.map.

See Also

• Including Facets in Search Results in the Search Developer's Guide
• Transforming Results with Map and Reduce in the Search Developer's Guide