Fixing RCLS Issues With Long Column Names In SQL

Nov 28, 2025 by Alex Johnson 49 views

Fixing Row and Column Level Security Issues with Long Column Names in SQL

Encountering issues with row and column level security (RCLS) when using SQL questions, especially on tables with long column names, can be frustrating. This article delves into the specifics of this problem, provides a step-by-step guide to reproduce the bug, and offers potential solutions to ensure your data remains secure and accessible. We'll explore common error messages, analyze log outputs, and discuss strategies to overcome these challenges. If you're grappling with RCLS implementation in your database environment, this guide is tailored to help you navigate these complexities.

Understanding the Bug: Long Column Names and RCLS

The core issue arises when row and column level security (RCLS) is implemented using SQL questions on tables where column names are excessively long. This is a common scenario in databases where detailed naming conventions are followed, or legacy systems have naming schemes that exceed typical length limits. The problem manifests as errors when the system attempts to apply RCLS rules, particularly when a non-admin user tries to access the table. The underlying cause is often the truncation or mangling of column names during the query processing, leading to mismatches between the expected and actual column identifiers. This section will explore the technical reasons behind this behavior and provide a solid foundation for understanding the solutions.

When setting up RCLS with a SQL question, the system generates SQL queries to enforce the security policies. These generated queries sometimes truncate column names due to database limitations or internal processing constraints. For instance, PostgreSQL has a default maximum identifier length of 63 characters. When column names exceed this limit, they are truncated, and the generated SQL will use these truncated names. However, the original SQL question might still refer to the full column names, creating a mismatch. This discrepancy leads to errors because the system cannot find the truncated columns in the original table definition. This issue highlights the importance of understanding database-specific limitations and how they interact with RCLS implementations.

Moreover, the process of aliasing columns can further complicate the matter. When you try to work around the truncation issue by explicitly aliasing columns in the SQL question, you might encounter a different set of errors. For example, if you use truncated names as aliases, the system might still fail because it expects the original, full names. This creates a scenario where the manual adjustments to the SQL question do not align with the system's internal expectations, leading to assertion failures and query processing errors. Understanding these nuances is crucial for crafting effective RCLS policies and troubleshooting issues.

In the subsequent sections, we will explore practical steps to reproduce this bug and examine the specific error messages and log outputs that arise. By understanding the problem's mechanics, we can better address the root causes and implement robust solutions.

Step-by-Step Guide to Reproduce the Bug

Reproducing the bug is essential for understanding its nature and verifying any potential fixes. Here’s a detailed, step-by-step guide to recreate the issue of row and column level security (RCLS) failing on tables with long column names:

Set up the Table: First, you need to create a table with excessively long column names. The example from the GitHub issue (https://github.com/metabase/metabase/issues/6409) provides a good starting point. Create a table named super_ridiculously_and_exceedingly_long_named_table_for_demonst with columns like column_name_with_an_incredibly_verbose_and_exceedingly_detailed, second_column_name_that_is_even_more_over_the_top_with_its_unne, etc. These names should be long enough to exceed the typical identifier length limits of your database system (e.g., 63 characters for PostgreSQL). This initial setup is crucial for triggering the bug.

Create a SQL Question: Next, create a SQL question that selects all columns from the newly created table. This question will serve as the basis for the RCLS rule. The SQL query should look something like this:

SELECT
column_name_with_an_incredibly_verbose_and_exceedingly_detailed,
second_column_name_that_is_even_more_over_the_top_with_its_unne,
third_column_name_that_continues_the_trend_of_being_excessively,
fourth_column_name_that_pushes_the_limits_of_postgresql_identif,
fifth_column_name_that_sets_a_new_record_for_unwarranted_prolix
FROM public.super_ridiculously_and_exceedingly_long_named_table_for_demonst;

This step is important because the SQL question will be used to define the RCLS policies, and any issues with column name handling will surface here.

Set up RCLS Permissions: Go to the permissions settings in your database management tool. For the user role you want to restrict (e.g., “All users”), configure RCLS for the table created in step 1. Use the SQL question from step 2 as the RCLS source. This means the results of the SQL question will determine which rows and columns the user can access. Additionally, ensure that the “Query builder usage” is allowed for the database. This setup ensures that non-admin users will be affected by the RCLS policies.
Log in as a Non-Admin User: Log in with a user account that does not have administrative privileges. This is necessary to test the effects of the RCLS rules. Accessing the table with a non-admin user will trigger the bug if the RCLS is not correctly configured.
Access the Table: Navigate to the table within the database management tool. If the bug is present, you should see an error message. The error often indicates that the system is expecting truncated column names that do not match the actual column names in the table. This is a key symptom of the issue.
Attempt Using Truncated Column Names: As a workaround, try modifying the SQL question to use the truncated column names. For example, if a column name is truncated to column_name_with_an_incredibly_verbose_and_exceedin_dabc7045, update the SQL query to include this truncated name as an alias:
```
SELECT
column_name_with_an_incredibly_verbose_and_exceedingly_detailed AS 
```