import { DuckDBService } from '../duckdb/service.js';
import { MCPConnectionPool } from './ConnectionPool.js';
import { ResourceRegistry } from './ResourceRegistry.js';
/**
 * Represents a federated query plan
 */
export interface QueryPlan {
    requiresFederation: boolean;
    localQuery?: string;
    remoteQueries: Map<string, string>;
    joinStrategy?: 'hash' | 'merge' | 'nested';
    estimatedCost?: number;
}
/**
 * Query execution result
 */
export interface QueryResult {
    data: any;
    metadata?: {
        rowCount: number;
        executionTime: number;
        sourcesQueried: string[];
    };
}
/**
 * Query Router for executing federated queries across multiple MCP servers
 * Handles query planning, routing, and result aggregation
 */
export declare class QueryRouter {
    private duckdb;
    private connectionPool;
    private resourceRegistry;
    private tempTableCounter;
    constructor(duckdb: DuckDBService, connectionPool: MCPConnectionPool, resourceRegistry: ResourceRegistry);
    /**
     * Analyze a SQL query and create an execution plan
     */
    analyzeQuery(sql: string): QueryPlan;
    /**
     * Execute a query with federation support
     */
    executeQuery(sql: string): Promise<QueryResult>;
    /**
     * Execute a federated query with streaming results
     */
    executeQueryStream(sql: string): AsyncGenerator<any, void, unknown>;
    /**
     * Fetch data from a remote MCP server
     */
    private fetchRemoteData;
    /**
     * Create a temporary table from remote data.
     *
     * The optional session pins all CREATE statements to the same connection so
     * the temp tables stay visible to the federated SELECT downstream. When
     * called without a session (legacy callers), falls back to executeQuery.
     */
    private createTempTable;
    /**
     * Clean up temporary tables. Session reuse keeps the DROP on the same
     * connection that issued the CREATE — required for routed hosts.
     */
    private cleanupTempTables;
    /**
     * Extract the query portion for a specific server
     */
    private extractServerQuery;
    /**
     * Prepare the local query with placeholders for remote data
     */
    private prepareLocalQuery;
    /**
     * Determine the best join strategy based on the query
     */
    private determineJoinStrategy;
    /**
     * Explain a federated query plan
     */
    explainQuery(sql: string): string;
    /**
     * Get query router statistics
     */
    getStats(): {
        tempTablesCreated: number;
        queriesRouted: number;
    };
}
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