Daily DAX : Day 403 INFO.STORAGETABLECOLUMNSEGMENTS

INFO.STORAGETABLECOLUMNSEGMENTS

Category: Diagnostic / Internal function (VertiPaq engine)

Availability: Only works in DirectQuery over Power BI datasets or when using XMLA endpoint with tools like DAX Studio or Tabular Editor.

What it does

Returns detailed information about how a column is physically segmented and stored inside the VertiPaq (in-memory columnar) engine of Power BI / Analysis Services Tabular models.

Syntax

INFO.STORAGETABLECOLUMNSEGMENTS(
    TableName,
    ColumnName
)

Parameters

ParameterDescription
TableNameName of the table (as string, e.g. "Sales")
ColumnNameName of the column (as string, e.g. "Order Date")

Returned Columns (simplified)

ColumnMeaning
SegmentNumberWhich data segment (1 segment ≈ 1 million rows)
RowsNumber of rows in that segment
DictionarySizeSize of value dictionary (bytes)
DataSizeSize of compressed column data (bytes)
CompressionTypeValue encoding + compression method
CardinalityDistinct values in the segment
MinValue / MaxValueRange of values in the segment

Typical Use Cases

  • Performance tuning – Identify columns with poor compression or very high cardinality segments.
  • Memory optimization – Find which columns/segments consume the most memory.
  • Understanding data distribution – See if new data is always added to the last segment (incremental load pattern).
  • Diagnosing refresh issues – Spot segments with abnormal size or bad compression.

Note: This function is not allowed in regular Power BI Desktop calculated columns or measures when the model is in Import mode. It only works via DirectQuery to a Premium workspace/dataset or through XMLA connectivity.

Example (run in DAX Studio against a Premium dataset)

EVALUATE
INFO.STORAGETABLECOLUMNSEGMENTS("Sales", "ProductKey")

This will show you exactly how the ProductKey column is split across segments and how well it is compressed — very useful when you wonder why a fact table is so large in memory.

Use this function during advanced model optimization in Power BI Premium or Azure Analysis Services.

Comments

Post a Comment

Popular posts from this blog

Daily DAX : Day 131 SELECTEDMEASURE

 The SELECTEDMEASURE function in Power BI's DAX (Data Analysis Expressions) language is a powerful tool used primarily within calculation groups to dynamically reference the measure currently being evaluated in a report. It’s part of the calculation group feature introduced to streamline complex reporting scenarios and improve maintainability by reducing the need to duplicate measure logic. What is SELECTEDMEASURE? SELECTEDMEASURE is a DAX function that returns a reference to the measure that is currently active or "selected" in the context of a calculation group. It doesn’t take any arguments and is typically used in the expression of a calculation item within a calculation group. This allows you to write generic logic that can dynamically apply to whichever measure is being evaluated in a visual, without hardcoding specific measure names. Syntax SELECTEDMEASURE()     Returns: A reference to the measure currently being evaluated in the report context. Use Case SELECTEDME...
Read more

Daily DAX : Day 446 INFO.CSDLMETADATA

Power BI DAX Function: INFO.CSDLMETADATA INFO.CSDLMETADATA` is a specialized DAX function introduced as part of a broader set of "INFO" functions (like `INFO.TABLES` or `INFO.MEASURES`) used for **model introspection**. It allows you to programmatically access the underlying structure of your Power BI semantic model. What does it do? The function returns a table with a single column containing the Conceptual Schema Definition Language (CSDL)  metadata of your model in XML format . In plain English, it exports a highly technical "blueprint" of your entire data model—including tables, columns, relationships, and measures—as a structured XML string. It is essentially the DAX equivalent of the `DISCOVER_CSDL_METADATA` Dynamic Management View (DMV) used in Analysis Services. --- Syntax and Output The syntax is straightforward as it requires no arguments: ```dax EVALUATE INFO.CSDLMETADATA() ``` Return Value : A table with one column and one row. Content : A long string ...
Read more

Daily DAX : Day 453 ENDOFWEEK

Power BI DAX Function: ENDOFWEEK Description The ENDOFWEEK function is a Time Intelligence function in DAX (Data Analysis Expressions) used in Power BI. It returns the date that represents the end of the week containing a specified date (typically Saturday, as weeks are considered to start on Sunday by default in DAX time intelligence). Syntax ENDOFWEEK( [, ]) : A column reference (usually from a Date table) or a date expression. Required. : Optional. Specifies the week-ending convention. Default is Saturday if omitted. Examples 1. Basic usage (default: week ends on Saturday): End of Week = ENDOFWEEK('Date'[Date]) For a date like January 8, 2026 (Thursday), this would return January 10, 2026 (Saturday). 2. In a measure for cumulative sales up to end of week: Total Sales to End of Week = CALCULATE( SUM(Sales[Amount]), DATESBETWEEN('Date'[Date], ST...
Read more