db-query-plan-analyzer

Overview

Most API perf regressions resolve to one of:

1. A new query running unindexed (sequential scan over a growing table).
2. A query joining on the wrong column type (implicit cast prevents index use).
3. A sort that doesn't fit in work_mem and spills to disk.
4. A query plan that started using a nested loop where a hash join would be faster (or vice versa) due to stale stats.
5. A query touching N+1 rows because of an ORM N+1 access pattern.