POST_START

Troubleshooting a Row Filter by Inspecting Its Function and Table Metadata

I recently encountered an issue with a row filter that wasn’t behaving as expected. The filter, defined as a function in Unity Catalog, was supposed to restrict access to customer data based on their region. However, some users were seeing data they shouldn’t have. I decided to investigate by inspecting the function and table metadata to understand what was going wrong.

Understanding the Row Filter Function

I started by checking the definition of the row filter function to see what columns it was using and how it was structured. I ran the DESCRIBE FUNCTION EXTENDED command on the region_filter function in the production.security schema.

DESCRIBE FUNCTION EXTENDED production.security.region_filter;

col_name	data_type	comment
customer_id	bigint	customer identifier
customer_name	string	customer display name
region	string	sales region

I noticed that the function included the customer_id, customer_name, and region columns. This made sense, as the filter was likely using the region to determine access. But I needed to confirm that the function was correctly referencing the table structure.

Verifying the Table Structure

To make sure the function was aligning with the actual table schema, I ran the DESCRIBE TABLE EXTENDED command on the customers table in the production.sales schema.

DESCRIBE TABLE EXTENDED production.sales.customers;

col_name	data_type	comment
customer_id	bigint	customer identifier
customer_name	string	customer display name
region	string	sales region

The table had the same columns as the function, which was a good sign. It confirmed that the function was likely referencing the correct columns. However, I wanted to see the actual data to understand if there were any discrepancies or edge cases that might be causing the issue.

Examining the Data

I decided to run a SELECT * FROM query on the customers table to get a closer look at the data and verify the values being used.

SELECT * FROM production.sales.customers;

customer_id	customer_name	region	status
1001	Maria Keller	EU	ACTIVE
1002	Daniel Smith	US	ACTIVE
1003	Sofia Rossi	EU	INACTIVE

From the data, I saw that some customers were marked as INACTIVE, but the filter was still allowing access. I realized that the filter might be using the region field to determine access, but it wasn’t taking into account the status field. That could explain why some users were seeing data they shouldn’t have.

Conclusion

By inspecting the function and table metadata, I was able to identify that the row filter was not considering the status field, which might be causing unexpected access. This insight helped me understand the root cause and paved the way for adjusting the filter logic to ensure it was correctly applied.