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Vitess vexplain¶
What it is¶
vexplain is Vitess's query-plan introspection surface — the Vitess analogue of MySQL's EXPLAIN, but aware of the sharding layer (which shards will be hit, how cross-shard joins will be assembled, which Vindexes will be consulted, etc.). As of Vitess 21, vexplain ships two new sub-commands:
vexplain trace— captures a detailed execution trace of a query across the distributed cluster, delivered as a JSON object for integration with external analysis tools. "This helps developers and DBAs analyze performance bottlenecks, review query plans, and gain visibility into how Vitess processes queries across distributed nodes."vexplain keys— analyses which columns a query touches in filters, groupings, and joins across tables, surfacing candidate columns for indexing, sharding, or optimization. Usable against standalone MySQL too, extending Vitess's tooling reach beyond Vitess-managed clusters.
Why it shows up on this wiki¶
vexplain is a canonical wiki instance of a sharding-aware EXPLAIN surface — MySQL's EXPLAIN is shard-oblivious and can't describe how a query fans out in a sharded topology. Vitess's vexplain is the operator-facing primitive that makes the sharding-layer's query plan legible. The vexplain keys mode extends the wiki's existing patterns/explain-before-execute-validation primitive from query-rewrite validation to schema-design analysis — what columns are actually used, which therefore merit indexes or become candidate sharding keys.
Seen in¶
- sources/2026-04-21-planetscale-announcing-vitess-21 — Vitess 21 introduces
vexplain trace+vexplain keysas new sub-commands. "By providing a clear view of column usage, vexplain keys makes it easier to fine-tune your database for better performance, regardless of your backend infrastructure." First canonical wiki datum onvexplainas an explicit observability surface;vexplain keysusable against standalone MySQL, extending Vitess's tooling reach.