Joins

SELECT * FROM a JOIN b ON a.id = b.id;
SELECT * FROM a LEFT JOIN b ON a.id = b.id;
SELECT * FROM a RIGHT JOIN b USING (id);
SELECT * FROM a FULL JOIN b ON a.id = b.id;
SELECT * FROM a CROSS JOIN b;   SELECT * FROM a, b;
SELECT * FROM users u, LATERAL jsonb_each(u.payload) AS e;
SELECT * FROM generate_series(1,3) AS g(n) WITH ORDINALITY;

JoinKind::{Inner,Left,Right,Full,Cross} (ast.rs). USING pre-expanded to equalities. FROM t x(a,b) derived column aliases supported.

Execution (join/support.rs)#

Nested-loop / hash / indexed / lateral shapes; SELECT * and t.* expansion in join order; ambiguous column → error; implicit lateral when RHS references outer columns.

What helps performance#

Equality and range join keys benefit from B-tree indexes; time-ordered joins benefit from ts indexes + zone-map pruning on columnar segments. Verify with EXPLAIN.