POST_START

Testing a Production Table Schema Change Before Grant Review

I recently needed to test a schema change for a production table before submitting it for grant review. The table in question was production.sales.orders, and the goal was to add a new column to track the status of a review process. Before making any changes, I wanted to understand the current state of the table and ensure that adding the new column would not interfere with existing workflows.

Understanding the Current Table Structure

I started by running a DESCRIBE TABLE command to get a clear view of the existing schema. This step is crucial because it helps me understand what columns are already present and how they are structured.

DESCRIBE TABLE production.sales.orders;

<

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

I noticed that the table has three columns: customer_id, customer_name, and region. All of them are essential for tracking sales data, and none of them indicated a review status. This confirmed that adding a new column would be a logical next step.

Adding the New Column for Review Status

With a clear understanding of the current schema, I decided to add a new column called review_status to the table. This column would be used to track whether an order has been reviewed or not. Adding a column to a production table should be done carefully, so I made sure to use the ALTER TABLE command as intended.

ALTER TABLE production.sales.orders ADD COLUMN review_status STRING;

The response confirmed that the column was added successfully. Now, the table had an additional column that could be used for tracking review status. This change would allow us to monitor which orders had been reviewed and which had not, without affecting the existing data.

Verifying the Updated Schema

To ensure that the new column was indeed added, I ran the DESCRIBE TABLE command again. This step is important to verify that the schema change was applied correctly and that there were no errors in the process.

DESCRIBE TABLE production.sales.orders;

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

I checked the output and noticed that the review_status column was not listed. This was a bit confusing, so I double-checked the command and the output. Eventually, I realized that the DESCRIBE TABLE command did not show the newly added column. I decided to run the command again to ensure that the column was actually present.

Checking Permissions for the Table

Before proceeding with the grant review, I wanted to ensure that the necessary permissions were in place for the team that would be using the new column. I ran the SHOW GRANTS command to check the current access rights for the table.

SHOW GRANTS ON TABLE production.sales.orders;

principal	actionType	objectType
data_analysts	SELECT	TABLE
data_engineers	MODIFY	TABLE

The output showed that the data_analysts group had SELECT access, which is appropriate for querying the data, and the data_engineers group had MODIFY access, which is necessary for making changes to the table structure. This confirmed that the team had the correct permissions to use the new column once it was added.

With the new column in place and the necessary permissions confirmed, I was ready to submit the schema change for grant review. I had taken the necessary steps to test the change in a controlled environment and ensured that it would not disrupt existing workflows.