ClickHouse's Thread Pool Wakes the Newest Idle Thread and Counts Events Per CPU
ClickHouse’s thread pool wakes the most recently idle thread, and its counters are sharded per CPU so that counting never costs a cache-line ping-pong.
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ClickHouse's Token-Bucket Throttler Sleeps Without Burning a CPU Slot
ClickHouse’s throttler is a token bucket that sleeps for the token deficit and parks the caller’s CPU lease so the wait need not consume concurrency budget.
How ClickHouse Spreads Parts Across Disks: the Storage Policy
ClickHouse places parts with a three-level reserve ladder: policy → volume → disk, with per-volume part-size limits and TTL-driven moves.
ClickHouse Shares a CPU Budget Between Queries with Fair CPU Slots
ClickHouse shares a global CPU-slot budget between queries with a max-min-fair scheduler, where each query’s slot ceiling is mutable and raised only when the pipeline finds real …
How ClickHouse Runs UNION, INTERSECT and EXCEPT
UNION ALL merges streams, UNION DISTINCT adds a hash DISTINCT with a self-abandoning preliminary pass, and INTERSECT/EXCEPT filter the left side through a set of the right.