1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
|
/**
* 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/>.
*/
#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
|