These settings are available in system.settings and are autogenerated from source.
timeout_overflow_mode
Sets what to do if the query is run longer than the max_execution_time or the
estimated running time is longer than max_estimated_execution_time (the
estimate is only checked with throw).
Possible values:
throw: throw an exception (default).break: stop executing the query and return the partial result, as if the
source data ran out. Some operations cannot return a partial result safely, so instead of a smaller
result they stop without producing one. A function computing a single value stops without producing
that value; whether the stop also reaches the client as a TIMEOUT_EXCEEDED error, or only as a
missing result, depends on where the query was interrupted. A Memory-table mutation left
incomplete by the timeout keeps the table unchanged and reports TIMEOUT_EXCEEDED. An INSERT may
report QUERY_WAS_CANCELLED. Some operations that wait for other replicas or for background work
do not stop at max_execution_time at all: a quorum write keeps waiting until its quorum is
satisfied, or reports UNKNOWN_STATUS_OF_INSERT if insert_quorum_timeout elapses first.
timeout_overflow_mode_leaf
Sets what happens when the query in leaf node run longer than max_execution_time_leaf.
Possible values:
throw: throw an exception (default).break: stop executing the query and return the partial result, as if the
source data ran out. Some operations cannot return a partial result safely, so
instead of a smaller result they stop without producing one: a function
computing a single value stops without producing that value. Whether such a stop
also reaches the client as a TIMEOUT_EXCEEDED error, or only as a missing
result, depends on where the query was interrupted.
Last modified on August 13, 2026
