SQL surface

KesselDB compiles SQL server-side against the live catalog. Supported surface (each item is covered by the test suite):

• DDL — CREATE TABLE, ALTER TABLE … ADD COLUMN (online, no lock), DROP TABLE, CREATE [UNIQUE|RANGE] INDEX, DROP INDEX, DESCRIBE, EXPLAIN.
• DML — INSERT … VALUES (…),(…)* (multi-row = one atomic op), UPDATE, DELETE.
• Queries — SELECT * | <projection> with WHERE (=, !=, <, <=, >,

  =, AND/OR/NOT, IN, BETWEEN, LIKE, IS [NOT] NULL), JOIN, GROUP BY, ORDER BY, LIMIT/OFFSET, COUNT/SUM/MIN/MAX/AVG.

• Constraints — NOT NULL, UNIQUE, foreign keys (ON DELETE RESTRICT/CASCADE/SET NULL), CHECK, deterministic triggers, deterministic WASM-MVP UDFs.
• Transactions — SQL BEGIN/COMMIT/ROLLBACK (atomic non-interactive write batch; reads inside BEGIN are rejected by design) plus op-level Op::Txn for the cluster path.

Full reference (every form, every keyword, every operator): Usage guide (full) §4–§6.