I wrote 400 lines to avoid learning one SQL feature
Window functions replaced a hand-rolled grouping pass. The cost of not learning was paid in code.
databases
5 posts
The index I added made the query slower, and the planner was right
Low selectivity plus random access beats a sequential scan only sometimes.
Offset pagination loses rows while you read, and the user never knows
An insert on page 1 shifts every later offset. A keyset cursor is data, not a position.
The N+1 query that looked fast in development
Ten rows locally, ten thousand in production. The query count scales with data.
The migration that could not be rolled back, and nobody noticed until it mattered
A column drop is irreversible the moment it runs. Expand-contract exists because deploys and migrations do not move together.