MondrianOlap

This article is for using the Mondrian OLAP server. If you use Mondrian, then you may encounter the following problems. These issues and their resolutions are described in the context of the default configuration file FoodMart.xml provided by Mondrian.

Mondrian parsing MDX to SQL leads to type conversion problem

For example: [Department].[All Departments].[1] parsed to SQL may result in department_id='1' because the department_id has no type, and the default type is String. The correct SQL would be department_id=1

Resolution

Specify the data type. For example:

<Dimension name="Department" foreignKey="department_id">
   <Hierarchy hasAll="true" primaryKey="department_id">
      <Table name="department"/>
      <Level name="Department Description" uniqueMembers="true"
         column="department_id" type="Numeric"/>
   </Hierarchy>
</Dimension>

Null type not correctly expressed in XML

Mondrian will return #null when data in the fact table is missing, but this causes the XML to not be parsed.

Resolution

Ensure that columns in the fact table that will be used as dimension level values do not contain nulls.

CalculatedMember caption problem

If a CalculatedMember tag has a caption different from the name, the XML returned by Mondrian will not discriminate the measures.

Resolution

Make the caption the same as the name or remove the caption:

<CalculatedMember name="Profit Growth" caption="Profit Growth">***</CalculatedMember>
<CalculatedMember name="Profit Growth">***</CalculatedMember>

Multiple Hierarchies Under the Same Dimension

Mondrian does not support selecting from multiple hierarchies that are the same dimension. For example, two different grouping levels of a date field. This is a known limitation of Mondrian, but in practice these queries tend to not make sense.