Clickhouse

ClickHouse Backs Up a Cluster with One Manifest: Sorting Gives Every File a Global Index

Oct 18, 2026 22 min read Jay Hubbert

A cluster-wide backup is a ZooKeeper-coordinated election: one owner per data file, a stage barrier between phases, and a consensus loop over metadata.

Clickhouse Backups Zookeeper Distributed Internals

ClickHouse Compiles a Date Format into a Program: Literal Text Becomes a memcpy Template

Oct 18, 2026 18 min read Jay Hubbert

formatDateTime compiles its format string into an instruction vector and a byte template.

Clickhouse Internals Performance Dates

ClickHouse Runs Regular Expressions Four Ways: Literals Never Reach RE2

Oct 18, 2026 35 min read Jay Hubbert

ClickHouse analyses a regexp before running it, and often never runs RE2 at all.

Clickhouse Internals Regexp Performance Jit

ClickHouse Parses URLs with a SIMD Byte Scanner: 27 Functions, No Regex Engine

Oct 18, 2026 24 min read Jay Hubbert

ClickHouse’s URL functions share a hand-rolled byte scanner instead of using a regex engine.

Clickhouse Internals Parsing Performance

ClickHouse Resolves a Function Call: A Signature String Chooses the Overload

Oct 18, 2026 30 min read Jay Hubbert

ClickHouse’s function factory: static registration, alias maps, and a declarative signature DSL for overload resolution.

Clickhouse Internals SQL Performance