Runs ONE SELECT/WITH/EXPLAIN inside a READ ONLY transaction that is always rolled back. Statements that modify data are rejected. Returns at most GUARD_QUERY_MAX_ROWS rows (default 1000) and says when the result was cut. Use it for investigation and analysis.

Runs ONE DML/DDL statement (UPDATE, INSERT, DELETE, ALTER, CREATE) in its own transaction, behind guardrails. Blocked: DELETE/UPDATE without their own WHERE (anywhere in the statement), TRUNCATE, DROP (except snapshot tables), ALTER ... DROP COLUMN, DO/CALL, BEGIN/COMMIT, SET and EXPLAIN. Requires i_understand=true when the statement changes more than GUARD_MAX_ROWS rows (default 1000), has a WHERE made only of constants (e.g. WHERE 1=1), or hides DML inside a WITH. Rolled back if it leaves a sequence behind MAX of its key. Commits only when every check passes, and writes an audit log entry.

Runs several statements inside ONE transaction: all of them commit, or none. Every statement goes through the same checks as execute. The sequence check runs after the last statement, so an INSERT with explicit keys can be followed by its setval. Use it for operations that must be atomic (e.g. backup + delete + insert).

Runs CREATE TABLE tmp_[_]_backup_YYYYMMDD AS SELECT * FROM [WHERE ...]. Use it BEFORE a destructive operation so a manual rollback is possible afterwards. The name must fit in 63 bytes. Returns the snapshot table name and the number of rows copied.