ClickHouse Computes Window Frames Incrementally, One Row at a Time
ClickHouse’s window transform advances a moving frame and updates the aggregate state incrementally instead of recomputing it per row.
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ClickHouse Deletes Rows by Writing a Mask, Not by Rewriting Data
ClickHouse’s lightweight DELETE stores a hidden _row_exists mask column and hardlinks every other column instead of rewriting them.
ClickHouse Encrypts Files at Rest with a 64-Byte Header
ClickHouse’s encrypted disk prepends a self-describing 64-byte header and AES-CTRs the payload beneath it.
ClickHouse Makes a MergeTree Part Visible with One Directory Rename
A MergeTree part is written to a temp directory through a stack of write buffers and published by one atomic directory rename.
ClickHouse Parses URLs with a Hand-Written State Machine
ClickHouse’s URL functions share a hand-rolled byte scanner instead of using a regex engine.