Push Ifs Up and Fors Down: The Idiom, Its Algebra, and Its Limits

The article examines the programming principle "push ifs up and fors down," which recommends moving conditional logic upward to callers while deferring loops to batch processing, improving code clarity and performance by centralizing branching and enabling vectorization. The principle extends beyond programming to database query optimization, where projections and selections are performed early to reduce data size before expensive operations like joins occur. The author argues this pattern reflects a broader concept applicable across relational databases and functional programming paradigms.