How ClickHouse's Sparse Column Stores Only the Rows That Differ
Real columns are mostly default. A status column is 'active' for 98% of rows and '' for the rest. A retries column is 0 almost always. An amount column that is Nullable is NULL for …
Performance
tmux Parses Escape Sequences Fast: Four Boring Optimisations That Matter
tmux’s parser has no clever trick in it. It’s a state machine with a transition cache, a bsearch(), a trie, and a width cache — four small optimisations, each of which swaps an…
PostgreSQL Speeds Up Hash Joins
A hash join is the simplest join algorithm in the database: build a hash table from the inner relation, then probe it once per outer row. There is no sort, no merge, no nested loop …
PostgreSQL Waits for Locks
Every lock in PostgreSQL is a bet. When a backend wants a resource that somebody else has, it has to choose: burn CPU waiting, or go to sleep and let the kernel schedule somebody …
PostgreSQL Locks Buffers Without LWLocks
Every time PostgreSQL reads a page it does two things: it pins the shared buffer that holds the page, and it takes a content lock on that buffer so that nobody rewrites the bytes …