reduceContext.key

Property Description

When the map/reduce process includes a map stage, the reduce keys are the keys written by mapContext.write(options).

When the map stage is skipped, the reduce keys are provided by the getInputData stage:

If the input type is an array, the key is the index of the element.
If the input type is an object, the key is the key in the object.
If the input type is a result set, the key is the internal ID of the result.

Note:

Each key cannot exceed 4000 bytes.

Type

string

Since

2015.2

Syntax

The following code snippet shows the syntax for this member. It is not a functional example. For a complete script example, see Map/Reduce Script Samples.

          ...
function reduce(context)
{
    context.write({
        key: context.key , 
        value: context.values.length 
    }); 
}
...

Syntax

Related Topics