Post aggregations

PostAggregations are specifications of processing that should happen on aggregated values as they come out of Druid. The available grammar is:

"postAggregations": [<post_aggregator>, ...],

post_aggregator: <arithmetic_aggregation>, <field_accessor>, <constant>

arithmetic_aggregation: {
    "type":"arithmetic",
    "fn":<arithmetic_function>,
    "field":[<post_aggregator>, <post_aggregator>, ...]
}
field_accessor: {"type":"fieldAccess", "fieldName":<field_name>}
constant: {"type":"constant", "value": <numerical_value>}

arithmetic_function: /, *, +, -

• arithmetic_aggregation – This applies the provided function to the fields from left to right.
• constant – This always returns the specified value
• field_accessor – This returns the value produced by an aggregator in the aggregations portion of the query