# Phase 24 — Query Performance Diagnostics

Builds on Phase 23.

- Adds a read-only index diagnostic section to the EXPLAIN inspector. Flags full scans with/without candidate indexes, and optimizer steps without a selected index.
- Adds per-step tabular EXPLAIN baseline comparisons for access type, selected index, possible indexes, estimated rows, filtered percentage, and Extra information.
- Adds **Copy Diagnostics** to copy SQL, plan observations, index analysis, and baseline differences.
- Preserves the Phase 23 query plan history and existing database management features.

## Important

The application has not been compiled in Xcode or tested against MySQL in this environment. The analysis uses optimizer estimates, not measured timings. It intentionally does not generate or apply CREATE INDEX statements. Compare plans only for equivalent schema/data conditions.