FIFO Locking in ALTER Queries Prevents Indefinite Blocking

Why it matters

This feature was created to address the problem where ALTER queries can be indefinitely blocked when there are continuously running queries accessing the same table. By using FIFO locking, ALTER queries are processed in the order they arrive, avoiding starvation and ensuring that schema modifications proceed in a timely manner.

How to use it

The FIFO locking mechanism for ALTER queries is enabled by default. Users do not need to change their query syntax or settings. When you execute an ALTER query on a table that has ongoing queries, the ALTER operation will queue behind existing queries and will not be blocked indefinitely.