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These settings are available in system.settings and are autogenerated from source.

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ast_fuzzer_any_query

When false (default), the server-side AST fuzzer (controlled by ast_fuzzer_runs) only fuzzes read-only queries (SELECT, EXPLAIN, SHOW, DESCRIBE, EXISTS). When true, all query types including DDL and INSERT are fuzzed.

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ast_fuzzer_runs

Enables the server-side AST fuzzer that runs randomized queries after each normal query, discarding their results.
  • 0: disabled (default).
  • A value between 0 and 1 (exclusive): probability of running a single fuzzed query.
  • A value >= 1: the number of fuzzed queries to run per normal query.
The fuzzer accumulates AST fragments from all queries across all sessions, producing increasingly interesting mutations over time. Fuzzed queries that fail are silently discarded; results are never returned to the client.
Last modified on July 24, 2026