pub type ExistsSet = (Vec<ColumnName>, BTreeSet<String>);Expand description
v7.34 (mailrs conn-pool-exhaustion P0) - decorrelated [NOT] EXISTS
semi/anti-join: the outer correlation columns (in key order) and the
set of encoded inner key-tuples that have >=1 matching inner row,
built in ONE scan. An outer row’s EXISTS reduces to a membership
test, turning O(outer x inner-exec) per-row work into O(scan + outer
lookups) - PG’s Hash Semi/Anti Join.