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Tracing a Production Table Query Failure Through Catalog, Schema, and Table Privileges

I was working on a critical data pipeline that was failing with an unexpected error. The query was attempting to access a table in the production catalog, but it was returning a permissions-related error. I needed to figure out why the query couldn’t access the table. My first thought was to check the privileges associated with the catalog, schema, and table in question.

Starting with the Catalog-Level Privileges

I started by running the SHOW GRANTS ON CATALOG production; command. This step is essential because it gives an overview of the permissions assigned at the catalog level. I wanted to confirm if the user had the necessary privileges to access any objects within the production catalog.

SHOW GRANTS ON CATALOG production;

The output showed that the user had the USAGE privilege on the production catalog, which allows access to the catalog but doesn’t grant direct access to tables or schemas. I realized that while the catalog-level access was sufficient, it wasn’t enough to interact with specific tables or schemas.

Checking Schema-Level Privileges

Next, I decided to check the privileges on the sales schema within the production catalog. I ran the command SHOW GRANTS ON SCHEMA production.sales;. This step helps determine if the user has the necessary permissions to access tables within a specific schema.

SHOW GRANTS ON SCHEMA production.sales;

The result indicated that the user had the USAGE privilege on the schema, which allows access to the schema and its contents. However, this still didn’t grant direct access to the table itself. I needed to dig deeper and check the table-level privileges.

Investigating Table-Level Privileges

To get more granular, I ran SHOW GRANTS ON TABLE production.sales.orders;. This command is crucial for identifying if the user has specific permissions like SELECT, INSERT, or UPDATE on the table in question.

SHOW GRANTS ON TABLE production.sales.orders;

Unfortunately, the output showed that the user didn’t have the SELECT privilege on the orders table. That explained why the query was failing—it didn’t have the necessary rights to read from the table.

Confirming with the Information Schema

To cross-verify, I used the system catalog to check the table privileges directly. I ran the query SELECT * FROM system.information_schema.table_privileges WHERE table_catalog = 'production' AND table_schema = 'sales' AND table_name = 'orders';. This approach ensures that I’m querying the actual system metadata, which is the source of truth for privilege information.

SELECT * FROM system.information_schema.table_privileges WHERE table_catalog = 'production' AND table_schema = 'sales' AND table_name = 'orders';

The result confirmed what I had already seen: the user lacked the SELECT privilege on the orders table. This was the root cause of the query failure.

Resolving the Issue

With the problem identified, I proceeded to grant the SELECT privilege on the orders table to the user. I used the command GRANT SELECT ON TABLE production.sales.orders TO user;. After applying the privilege, the query ran successfully, and the pipeline resumed its normal operation.

This experience taught me the importance of checking privileges at each level—catalog, schema, and table—when troubleshooting access issues. It’s a common pitfall to assume that catalog-level access is sufficient, but in reality, table-level permissions are often the missing piece.