PostgreSQL index design is often misunderstood. Many developers think that creating a good index simply means: “Create an index containing the columns from the WHERE clause.” In reality, efficient index design is far more nuanced. The order of columns inside a composite index matters enormously, and the best choice depends on: Predicate types ( = , >= , BETWEEN , LIKE , etc.) Column selectivity Table size PostgreSQL planner statistics Actual execution plans This article explains the core principles behind efficient PostgreSQL index design before showing how pgAssistant automates this process using execution plans and database statistics. Why Index Design Is Difficult Consider the following query: SELECT order_id , customer_id , employee_id , order_date , ship_country FROM public .…