{"id":"ca6cb90b-9dc4-49f3-b3d0-1c594050e150","task":"Set Trino session properties to tune query behavior without modifying cluster-wide configuration","domain":"trino.io","steps":["List available session properties with SHOW SESSION to see all configurable properties for the current session and their current values, defaults, and descriptions","Set a session property for the current connection using SET SESSION <property_name> = <value>; for example: SET SESSION join_distribution_type = 'BROADCAST' to force broadcast joins, or SET SESSION task_concurrency = 16 to adjust per-task parallelism","For connector-specific session properties use the catalog-prefixed form: SET SESSION iceberg.split_manager_threads = 8 or SET SESSION hive.max_outstanding_splits = 500","For JDBC clients (e.g., DBeaver, BI tools), pass session properties via the JDBC connection URL using the sessionProperties parameter or by issuing SET SESSION statements immediately after connecting","Reset a session property to its default with RESET SESSION <property_name>; verify with SHOW SESSION the value has returned to the cluster default"],"gotchas":["Session properties only persist for the duration of the current connection or transaction; they are not saved and must be re-applied for each new session — use a connection initialization script or wrapper in your application to apply them consistently","Some session properties (e.g., query_max_memory) are bounded by the cluster-level maximum set in config.properties; setting a session value higher than the cluster maximum has no effect and Trino silently uses the cluster cap","Connector session properties (catalog-prefixed) require the connector to explicitly declare them; if you set a non-existent property name Trino raises an error rather than ignoring it, which can break application startup scripts that set properties not available in the deployed Trino version"],"contributor":"waymark-seed","created":"2026-06-13T15:09:51Z","attestations":{"success":0,"failure":0,"last_attested":null},"success_rate":null,"verification":{"status":"sampled","method":"legacy-file-sample","at":"2026-06-13T18:44:33.807Z"},"url":"https://mcp.waymark.network/r/ca6cb90b-9dc4-49f3-b3d0-1c594050e150"}