Multiple Measures and Aggragators

Data cubes can also have multiple measures when different aggregations are required for a column.

Database Schema

The cube defined in this example is based on a single table that stores all the data. The table, named Fact, contains two columns: KEY and VALUE. The KEY column acts as a discriminator, while the VALUE column holds the measurements to be aggregated.

<roma:DatabaseSchema   id="databaseSchema">
  <tables xsi:type="roma:PhysicalTable" id="_tab" name="Fact">
    <columns xsi:type="roma:PhysicalColumn" id="_col_key" name="KEY"/>
    <columns xsi:type="roma:PhysicalColumn" id="_col" name="VALUE" type="Integer"/>
  </tables>
</roma:DatabaseSchema>

Note: This is only a symbolic example. For the exact definition, see the Definition section.

Query

This example uses a TableQuery, as it directly references the physical table Fact.

<roma:TableQuery  id="_query" table="_tab"/>

Note: This is only a symbolic example. For the exact definition, see the Definition section.

Cube, MeasureGroup and Measure

In this example, multiple measures are defined. All measures reference the VALUE column and use the following aggregation functions:

• SUM – Calculates the sum of the values.
• MIN – Retrieves the minimum value.
• MAX – Retrieves the maximum value.
• AVG – Computes the average of the values.

<roma:PhysicalCube   id="_cube" name="MeasuresAggregatorsCube" query="_query">
  <measureGroups>
    <measures xsi:type="roma:SumMeasure" id="_measure1" name="Sum of Value" column="_col"/>
    <measures xsi:type="roma:MaxMeasure" id="_measure2" name="Max of Value" column="_col"/>
    <measures xsi:type="roma:MinMeasure" id="_measure3" name="Min of Value" column="_col"/>
    <measures xsi:type="roma:AvgMeasure" id="_measure4" name="Avg of Value" column="_col"/>
  </measureGroups>
</roma:PhysicalCube>

Note: This is only a symbolic example. For the exact definition, see the Definition section.

Definition

This files represent the complete definition of the catalog.

<?xml version="1.0" encoding="UTF-8"?>
<xmi:XMI xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:roma="https://www.daanse.org/spec/org.eclipse.daanse.rolap.mapping">
  <roma:Catalog name="Measure - Basic Aggregators" cubes="_cube" dbschemas="databaseSchema"/>
  <roma:DatabaseSchema id="databaseSchema">
    <tables xsi:type="roma:PhysicalTable" id="_tab" name="Fact">
      <columns xsi:type="roma:PhysicalColumn" id="_col_key" name="KEY"/>
      <columns xsi:type="roma:PhysicalColumn" id="_col" name="VALUE" type="Integer"/>
    </tables>
  </roma:DatabaseSchema>
  <roma:TableQuery id="_query" table="_tab"/>
  <roma:PhysicalCube id="_cube" name="MeasuresAggregatorsCube" query="_query">
    <measureGroups>
      <measures xsi:type="roma:SumMeasure" id="_measure1" name="Sum of Value" column="_col"/>
      <measures xsi:type="roma:MaxMeasure" id="_measure2" name="Max of Value" column="_col"/>
      <measures xsi:type="roma:MinMeasure" id="_measure3" name="Min of Value" column="_col"/>
      <measures xsi:type="roma:AvgMeasure" id="_measure4" name="Avg of Value" column="_col"/>
    </measureGroups>
  </roma:PhysicalCube>
</xmi:XMI>

Turorial Zip

This files contaisn the data-tables as csv and the mapping as xmi file.

Download Zip File