Analysis of the Error and Solution

The error DelimitedTextMoreColumnsThanDefined occurs when Azure Data Factory (ADF) attempts to process a file as delimited text (CSV/TSV) but encounters more columns than expected in the data structure. In this specific case:

• Key Observation: The source file 0_2020_11_09_11_43_32.avro is an Avro file, but ADF is incorrectly trying to process it as Csv/Tsv Format Text.
• Root Cause: ADF is attempting schema validation and parsing the Avro file as if it were a delimited text file, which causes the column mismatch error.

Evaluation of Options

✅ Option A: Change the Copy activity setting to Binary Copy

• Optimal Solution: Binary Copy treats files as binary objects without attempting to parse or validate their content structure.
• Why It Works: Since the requirement is simply to copy files between folders (Folder1 to Folder2), Binary Copy bypasses schema validation entirely, copying the Avro files exactly as they are.
• Best Practice: This approach is recommended for bulk file migration scenarios where data transformation is not required, especially when dealing with binary formats like Avro, Parquet, or mixed file types.

❌ Option B: Lower the degree of copy parallelism

• Not Relevant: This setting affects performance and throughput but does not address the fundamental schema parsing issue causing the error.
• Impact: Reducing parallelism might slow down the copy operation but won't resolve the column mismatch problem.

❌ Option C: Add an explicit mapping

• Inappropriate for This Scenario: Explicit mapping requires ADF to parse and understand the file structure, which is exactly what's causing the error with Avro files.
• Limitation: Since ADF is incorrectly interpreting the Avro file as CSV/TSV, explicit mapping would still fail because the underlying parsing mechanism is wrong for the file format.

❌ Option D: Enable fault tolerance to skip incompatible rows

• Suboptimal Approach: While this would allow the copy to continue by skipping problematic rows, it results in data loss.
• Not Recommended: The error occurs because ADF is using the wrong parsing method for Avro files, not because the data itself is inherently incompatible. Skipping rows would discard valid Avro data.

Conclusion

Binary Copy (Option A) is the correct solution because it addresses the root cause: ADF should not attempt to parse Avro files as delimited text. This approach ensures complete data preservation while efficiently accomplishing the file copy operation between ADLS Gen2 folders.