ClickHouse Stores a TTL as Two Timestamps Per Part: Expired Rows Vanish at Merge Time
ClickHouse stores a per-part TTL expiry bound and removes expired rows during a merge, using a bit mask rather than a rewrite.
Posts
All posts published on this site.
Everything published here, newest first.
ClickHouse Attaches Row Policies to the Table Read: Permissive OR, Restrictive AND
ClickHouse mixes row policies into one boolean expression and injects it into the query plan as a filter on the table read.
ClickHouse Splits Session State from Query State: SET and SETTINGS Land in Different Contexts
ClickHouse splits session state from per-query state, and gates every setting change through a constraint checker.
ClickHouse Resolves an INSERT Into a Sample Block: The Client's Column Order Wins
ClickHouse resolves an INSERT’s columns by name into a sample block, then squashes, dedup-stamps and fans the data out to the sinks.
ClickHouse's numbers() Is a Generator, Not a Table: One Iota-Filled Block at a Time
numbers() is a generator that iota-fills one column per block and keeps only a counter in memory.