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/**
* Copyright (C) 2008 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/db/query_plan_selection_policy.h"
namespace mongo {
class Cursor;
class ParsedQuery;
struct QueryPlanSummary;
/**
* @return a cursor interface to the query optimizer. The implementation may utilize a
* single query plan or interleave results from multiple query plans before settling on a
* single query plan. Note that the schema of currKey() documents, indexKeyPattern(), the
* matcher(), and the isMultiKey() nature of the cursor may change over the course of
* iteration.
*
* @param query - Query used to select indexes and populate matchers; not copied if unowned
* (see bsonobj.h).
*
* @param order - Required ordering spec for documents produced by this cursor, empty object
* default indicates no order requirement. If no index exists that satisfies the required
* sort order, an empty shared_ptr is returned unless parsedQuery is also provided. This is
* not copied if unowned.
*
* @param planPolicy - A policy for selecting query plans - see queryoptimizercursor.h
*
* @param parsedQuery - Additional query parameters, as from a client query request.
*
* @param requireOrder - If false, the resulting cursor may return results in an order
* inconsistent with the @param order spec. See queryoptimizercursor.h for information on
* handling these results properly.
*
* @param singlePlanSummary - Query plan summary information that may be provided when a
* cursor running a single plan is returned.
*
* The returned cursor may @throw inside of advance() or recoverFromYield() in certain error
* cases, for example if a capped overrun occurred during a yield. This indicates that the
* cursor was unable to perform a complete scan.
*
* This is a work in progress. Partial list of features not yet implemented through this
* interface:
*
* - covered indexes
* - in memory sorting
*/
shared_ptr<Cursor> getOptimizedCursor( const StringData& ns,
const BSONObj& query,
const BSONObj& order = BSONObj(),
const QueryPlanSelectionPolicy& planPolicy =
QueryPlanSelectionPolicy::any(),
const shared_ptr<const ParsedQuery>& parsedQuery =
shared_ptr<const ParsedQuery>(),
bool requireOrder = true,
QueryPlanSummary* singlePlanSummary = NULL );
/**
* @return a single cursor that may work well for the given query. A $or style query will
* produce a single cursor, not a MultiCursor.
* It is possible no cursor is returned if the sort is not supported by an index. Clients
* are responsible for checking this if they are not sure an index for a sort exists, and
* defaulting to a non-sort if no suitable indices exist.
*/
shared_ptr<Cursor> getBestGuessCursor( const char* ns,
const BSONObj& query,
const BSONObj& sort );
} // namespace mongo
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