PostgreSQL Migrations Skill Common PostgreSQL Migration Errors and Solutions 1. "Subquery uses ungrouped column from outer query" Cause : Subquery in SELECT/CASE references columns from outer query that aren't in GROUP BY. Solution : Use CTE (Common Table Expression) to separate aggregation from subqueries: 2. "Functions in index expression must be marked IMMUTABLE" Cause : PostgreSQL requires functions in indexes/generated columns to be IMMUTABLE. Problem Functions : - - marked STABLE, not IMMUTABLE - - depends on timezone/locale settings - - changes over time Solution : Create IMMUTABLE wra…