Metric Parameter for Object Queries (OLAP)

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OLAP Object Queries: Metric Parameter for Object Queries

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In an object query, the metric parameter returns one or more metric computations for each selected object. These computed values are in addition to the field values specified by the fields parameter. The syntax for the metric parameter is the same as in aggregate queries: it is a comma-separated list of metric expressions. Each metric expression is an algebraic expression using metric functions, arithmetic operators, and parentheses. See the section [Metric Parameter for Aggregate Queries](https://github.com/dell-oss/Doradus/wiki/Metric Parameter for Aggregate Queries (OLAP)) for full details. Below is an example object query with a single metric function:

GET /Email/Person/_query?shards=s1&m=COUNT(Messages.MessageAsSender)&f=FirstName,LastName

This query selects all Person objects and returns their FirstName and LastName fields. Additionally, the metric parameter returns the COUNT of all Messages.MessageAsSender values for each object. The metric expression result is returned as an additional field element whose name equals the metric expression text. Example:

<results>
    <totalobjects>185</totalobjects>
    <docs>
        <doc>
            <field name="COUNT(Messages.MessageAsSender)">3</field>
            <field name="FirstName">Chris</field>
            <field name="LastName">Rudd</field>
            <field name="_ID">+IBGjRcg4dMXgu3l7aOZXg==</field>
            <field name="_shard">s1</field>
        </doc>
        <doc>
            <field name="COUNT(Messages.MessageAsSender)">9</field>
            <field name="FirstName">Scott</field>
            <field name="LastName">Reasoner</field>
            <field name="_ID">+eVQDWAtRBSjWc6DHYVtTg==</field>
            <field name="_shard">s1</field>
        </doc>
        ...
    </docs>
<results>

The field name used for the metric function can be customized for easier recognition using the AS syntax. Example:

GET /Email/Person/_query?shards=s1&m=COUNT(Messages.MessageAsSender) AS 'Messages Sent'

&f=FirstName,LastName

The name following AS can be a simple term or a quoted string. Multiple expressions can be computed by the metrics parameter by separating each expression by a comma. For example, suppose we want to know the total number of messages sent by each person and the total size of all sent messages. The following query could be used:

GET /Email/Person/_query?range=0&f=FirstName,LastName

&m=COUNT(Messages.MessageAsSender) AS TotalMessages, SUM(Messages.MessageAsSender.Size) AS TotalSize

Below is an example where a metric computation uses an algebraic expression to compute a more complex result:

GET /Email/Person/_query?range=0&f=FirstName,LastName

&m=COUNT(DirectReports^.WHERE(LastName:smith)) + COUNT(Manager^.WHERE(Department:support))

In addition to FirstName and LastName, this query returns for each person the sum of (1) the count of all DirectReports transitively (“down” the org chart) whose LastName contains the term “smith”, and (2) the count of all Managers transitively (“up” the org chart) whose Department contains the term “support”.