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Medium severitydata flow

Power BI Refresh Error:
DF-Executor-Conversion

What does this error mean?

A data type conversion failed during the data flow transformation. A column value cannot be cast from its source type to the target type — for example, a string column containing 'N/A' being cast to an integer, or a date string in the wrong format being parsed to a date type.

Common causes

  • 1A source column contains string values that cannot be parsed as the target numeric or date type (e.g., 'N/A', empty strings, or locale-formatted numbers like '1.234,56')
  • 2A null value is being passed to a cast function that does not handle nulls — for example, toInteger(null) fails without an iifNull guard
  • 3A date or timestamp string is in a format that does not match the format pattern used in the toDate() or toTimestamp() expression
  • 4The source schema changed and a column that was previously a numeric type is now sent as a string
  • 5An implicit type coercion occurs in a Derived Column that tries to combine incompatible types (e.g., adding a string to an integer)

How to fix it

  1. 1Identify the failing column and data type in the ADF activity run output — the error message names the column and the source/target type combination.
  2. 2Add an explicit cast in a Derived Column transformation before the sink: use `toInteger()`, `toString()`, `toDate()`, or the appropriate conversion expression.
  3. 3If source values may be null or unparseable, wrap the cast in an `iif(isNull(col), null, toInteger(col))` expression to handle edge cases.
  4. 4Enable fault tolerance in the data flow settings to skip incompatible rows and log them to a separate output.
  5. 5Use debug mode to preview the source data and confirm which values are causing the type conversion failure.

Frequently asked questions

How do I safely cast a column that may contain non-numeric values?

Use an iif expression to check before casting: iif(isNan(toDouble(col)) || isNull(col), null, toInteger(col)). This returns null for unparseable values instead of failing. Alternatively, use fault tolerance to redirect rows that fail conversion.

How do I parse dates with a specific format?

Use toDate(col, 'yyyy-MM-dd') or toTimestamp(col, 'yyyy-MM-dd HH:mm:ss') with explicit format strings. For multiple date formats, use iif expressions to detect the format and route to the appropriate parse expression.

Does this error appear on every run or only sometimes?

It depends on the data — a value in every batch fails every run; a value in specific records fails only when they arrive. Use debug mode with data preview to identify failing values.

Will downstream Power BI datasets be affected?

Yes — unless fault tolerance is enabled, the pipeline fails and no data reaches the target. Dependent datasets serve stale figures.

Official documentation: https://learn.microsoft.com/en-us/azure/data-factory/data-flow-troubleshoot-guide

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