ClickHouse Caches Remote Objects as Local File Segments
ClickHouse’s filesystem cache stores remote objects as size-encoded local segment files ordered by an in-memory LRU.
Internals
ClickHouse Compiles a Date Format String into a Program
formatDateTime compiles its format string into an instruction vector and a byte template.
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.
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.