Safe Online Schema Migrations

Problem

Adding a column with a default value to a large table in production can cause an exclusive lock, locking out web requests. Write a query that outputs a best practice as best_practice with the value: "To safely add a default value to a large table, add the column without a default first, then apply the default for new rows, and backfill existing rows in batches."

Database Schema

This problem acts as a scratchpad. You will write your own DDL/DML or conceptual queries, so there is no predefined schema.

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Hint

Solution