import type { SQLSourceRequest } from '../lang/translate-response';
import type { MalloyQueryData, QueryRunStats, SQLSourceDef, StructDef, TableSourceDef } from '../model/malloy_types';
import type { RunSQLOptions } from '../run_sql_options';
import type { Connection, FetchSchemaOptions, PersistSQLResults, PooledConnection, StreamingConnection } from './types';
export interface SchemaFound<T extends StructDef> {
    schema: T;
    error?: undefined;
    timestamp: number;
}
export interface SchemaNotFound {
    schema?: undefined;
    error: string;
}
export type CachedSchema<T extends StructDef> = SchemaFound<T> | SchemaNotFound;
export declare abstract class BaseConnection implements Connection {
    abstract runSQL(sql: string, options?: RunSQLOptions | undefined): Promise<MalloyQueryData>;
    abstract get name(): string;
    abstract get dialectName(): string;
    abstract fetchTableSchema(tableName: string, tablePath: string): Promise<TableSourceDef | string>;
    abstract fetchSelectSchema(sqlSource: SQLSourceRequest): Promise<SQLSourceDef | string>;
    protected schemaCache: Record<string, CachedSchema<StructDef>>;
    protected checkSchemaCache<T extends StructDef>(schemaKey: string, schemaType: 'table' | 'sql_select', fillCache: () => Promise<T | string>, refreshTimestamp: number | undefined): Promise<CachedSchema<T>>;
    fetchSchemaForTables(missing: Record<string, string>, { refreshTimestamp }: FetchSchemaOptions): Promise<{
        schemas: Record<string, TableSourceDef>;
        errors: Record<string, string>;
    }>;
    fetchSchemaForSQLStruct(sqlRef: SQLSourceRequest, { refreshTimestamp }: FetchSchemaOptions): Promise<{
        structDef: SQLSourceDef;
        error?: undefined;
    } | {
        error: string;
        structDef?: undefined;
    }>;
    isPool(): this is PooledConnection;
    canPersist(): this is PersistSQLResults;
    canStream(): this is StreamingConnection;
    close(): Promise<void>;
    estimateQueryCost(_sqlCommand: string): Promise<QueryRunStats>;
    fetchMetadata(): Promise<{}>;
    fetchTableMetadata(_tablePath: string): Promise<{}>;
}