/**
 * Lightweight read-only SQL guard.
 *
 * The primary safety mechanism for user-supplied queries is opening the DuckDB
 * connection in `READ_ONLY` access mode — the engine itself rejects mutating
 * statements with a clear error. This guard is belt-and-braces: it catches
 * obviously-bad inputs before they hit the engine, and blocks extension /
 * configuration commands (INSTALL / LOAD / ATTACH / PRAGMA) that DuckDB does
 * permit in read-only mode and that would let a caller reach outside the
 * sandbox.
 */
export declare class SqlGuardError extends Error {
    constructor(message: string);
}
/**
 * Reject any SQL that is not a single read-only statement. Call this before
 * handing `sql` to DuckDB on a read-only connection.
 */
export declare function assertReadOnlySql(sql: string): void;
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