import type { DatabaseConnector, ConnectionConfig, TableInfo, ColumnInfo } from '../connector.js';
import type { QueryResult } from '../result-types.js';
/**
 * FileConnector — uses DuckDB under the hood to query CSV, Parquet, JSON,
 * and Excel files directly with SQL.
 *
 * Usage in dql.config.ts:
 *   { driver: 'file', filepath: ':memory:' }
 *
 * Then in .dql files:
 *   SELECT * FROM read_csv('./data/sales.csv')
 *   SELECT * FROM read_parquet('./data/events.parquet')
 *   SELECT * FROM read_json('./data/config.json')
 */
export declare class FileConnector implements DatabaseConnector {
    readonly driverName = "file";
    private duckdb;
    constructor();
    connect(config: ConnectionConfig): Promise<void>;
    execute(sql: string, params?: unknown[]): Promise<QueryResult>;
    disconnect(): Promise<void>;
    ping(): Promise<boolean>;
    listTables(): Promise<TableInfo[]>;
    listColumns(schema?: string, table?: string): Promise<ColumnInfo[]>;
}
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