Power Pivot Principles: The A to Z of DAX Functions – INFO.LEVELS

In our long-established Power Pivot Principles articles, we continue our series on the A to Z of Data Analysis eXpression (DAX) functions.  This week, we look at INFO.LEVELS.

The INFO.LEVELS function

Dynamic Management Views (DMVs) are specialised queries provided by SQL Server Analysis Services (SSAS), Azure Analysis Services (AAS), and Power BI that offer an administrative view into the internal state of these systems.  DMVs are used to retrieve metadata, monitor health and performance, and diagnose problems within the database or data model.  They serve as a powerful tool for administrators and developers to gain insights into the workings of the database engine and the tabular data model, covering aspects like performance metrics, configuration settings and the structure of database objects.

The $System schema DMVs in SQL Server Analysis Services (SSAS), Azure Analysis Services (AAS), and Power BI are categorised into four [4] types, each serving specific purposes:

• DISCOVER: requires admin privileges and provides information about the model, including details on connected sessions and environment configuration
• DMSCHEMA: focused on data mining, offering insights for predictive analytics and pattern recognition, mainly used in SSAS/AAS
• MDSCHEMA: targets multidimensional models, delivering metadata and structure from an MDX perspective, relevant for OLAP cubes and dimensions
• TMSCHEMA: designed for tabular models, it provides detailed metadata about tables, columns, measures, etc., using Tabular Model Scripting Language (TMSL) information, crucial for Power BI and tabular SSAS/AAS models.

In the past, if we wanted to query those $System schema DMVs we used external tools like Tabular Editors or DAX Studio to query them:

The INFO.LEVELS function is one of the system functions.  It employs the following syntax:

INFO.LEVELS()

This function has no parameters.

Based upon the ‘[MS-SSAS-T]: SQL Server Analysis Services Tabular Protocol’ from Microsoft (which you may access here), the Level object represents a level in a hierarchy that provides a logical hierarchical drilldown path for client applications.  It is a child of a Hierarchy object.  The level is based on the values in a column.

We can write this INFO.LEVELS function on DAX query view to get the same information on the TMSCHEMA_LEVELS:

It will query the $SYSTEM.TMSCHEMA_LEVELS and return an entire table with nine [9] columns:

• ID: this is a reference to the object
• HierarchyID: this is ID-based reference to a Hierarchy object
• Ordinal: this is the position of the level within the hierarchy.  The levels in the hierarchy MUST be properly ordered, starting with 0 and increasing monotonically
• Name: this is the name of the object
• Description: this is the description of the object
• ColumnID: this is an ID-based reference to a Column object
• ModifiedTime: this is the time that the object was last modified
• LineageTag: this is an optional tag that can be used to define the lineage of a level across different versions of a model.  Compatibility level 1600 or higher is required
• SourceLineageTag: this is an optional tag that can be used to define the lineage of a referenced level across different versions of a model.  As opposed to LineageTag, SourceLineageTag can be used to define the lineage of a referenced level rather than a level itself.  SourceLineageTag is useful when a model references other models by using a Direct Query connection.  Compatibility level 1600 or higher is required.

It should be noted that:

• it is used for querying the DMV (Dynamic Management Views) from the $System schema called TMSCHEMA where TM stand for ‘Tabular model’ and TMSCHEMA provides information from the tabular model
• sometimes querying DMVs may fail if we do not have the appropriate permission
• there is also a MDSCHEMA for LEVELS call MDSCHEMA_ LEVELS but its output is not the same as TMSCHEMA_LEVELS and INFO.LEVELS.

Come back next week for our next post on Power Pivot in the Blog section.  In the meantime, please remember we have training in Power Pivot which you can find out more about here.  If you wish to catch up on past articles in the meantime, you can find all of our Past Power Pivot blogs here.