mongo::Query Class Reference

Represents a Mongo query expression. More...

#include <dbclientinterface.h>

Public Member Functions
	Query (const BSONObj &b)
	Query (const string &json)
	Query (const char *json)
Query &	sort (const BSONObj &sortPattern)
	Add a sort (ORDER BY) criteria to the query expression. More...
Query &	sort (const string &field, int asc=1)
	Add a sort (ORDER BY) criteria to the query expression. More...
Query &	hint (BSONObj keyPattern)
	Provide a hint to the query. More...
Query &	hint (const string &jsonKeyPatt)
Query &	minKey (const BSONObj &val)
	Provide min and/or max index limits for the query. More...
Query &	maxKey (const BSONObj &val)
	max is exclusive
Query &	explain ()
	Return explain information about execution of this query instead of the actual query results. More...
Query &	snapshot ()
	Use snapshot mode for the query. More...
Query &	where (const string &jscode, BSONObj scope)
	Queries to the Mongo database support a $where parameter option which contains a javascript function that is evaluated to see whether objects being queried match its criteria. More...
Query &	where (const string &jscode)
Query &	readPref (ReadPreference pref, const BSONArray &tags)
	Sets the read preference for this query. More...
bool	isComplex (bool *hasDollar=0) const
BSONObj	getFilter () const
BSONObj	getSort () const
BSONObj	getHint () const
bool	isExplain () const
string	toString () const
	operator string () const

Static Public Member Functions
static bool	isComplex (const BSONObj &obj, bool *hasDollar=0)
static bool	hasReadPreference (const BSONObj &queryObj)

Public Attributes
BSONObj	obj

Static Public Attributes
static const BSONField< BSONObj >	ReadPrefField
static const BSONField < std::string >	ReadPrefModeField
static const BSONField< BSONArray >	ReadPrefTagsField

Detailed Description

Represents a Mongo query expression.

Typically one uses the QUERY(...) macro to construct a Query object. Examples: QUERY( "age" << 33 << "school" << "UCLA" ).sort("name") QUERY( "age" << GT << 30 << LT << 50 )

Member Function Documentation

Query & mongo::Query::explain

(

)

Return explain information about execution of this query instead of the actual query results.

Normally it is easier to use the mongo shell to run db.find(...).explain().

bool mongo::Query::hasReadPreference ( const BSONObj &  queryObj )

static

Returns

true if the query object contains a read preference specification object.

Query & mongo::Query::hint

(

BSONObj

keyPattern

)

Provide a hint to the query.

Parameters

keyPattern

Key pattern for the index to use. Example: hint("{ts:1}")

bool mongo::Query::isComplex

(

bool *

hasDollar = 0

)

const

Returns

true if this query has an orderby, hint, or some other field

Query & mongo::Query::minKey

(

const BSONObj &

val

)

Provide min and/or max index limits for the query.

min <= x < max

Query & mongo::Query::readPref	(	ReadPreference	pref,
		const BSONArray &	tags
	)

Sets the read preference for this query.

Parameters

pref	the read preference mode for this query.
tags	the set of tags to use for this query.

Query & mongo::Query::snapshot

(

)

Use snapshot mode for the query.

Snapshot mode assures no duplicates are returned, or objects missed, which were present at both the start and end of the query's execution (if an object is new during the query, or deleted during the query, it may or may not be returned, even with snapshot mode).

Note that short query responses (less than 1MB) are always effectively snapshotted.

Currently, snapshot mode may not be used with sorting or explicit hints.

Query & mongo::Query::sort

(

const BSONObj &

sortPattern

)

Add a sort (ORDER BY) criteria to the query expression.

Parameters

sortPattern

the sort order template. For example to order by name ascending, time descending: { name : 1, ts : -1 } i.e. BSON( "name" << 1 << "ts" << -1 ) or fromjson(" name : 1, ts : -1 ")

Query& mongo::Query::sort ( const string &  field, int  asc = 1  )

inline

Add a sort (ORDER BY) criteria to the query expression.

This version of sort() assumes you want to sort on a single field.

Parameters

asc	= 1 for ascending order asc = -1 for descending order

Query & mongo::Query::where	(	const string &	jscode,
		BSONObj	scope
	)

Queries to the Mongo database support a $where parameter option which contains a javascript function that is evaluated to see whether objects being queried match its criteria.

Use this helper to append such a function to a query object. Your query may also contain other traditional Mongo query terms.

Parameters

jscode	The javascript function to evaluate against each potential object match. The function must return true for matched objects. Use the this variable to inspect the current object.
scope	SavedContext for the javascript object. List in a BSON object any variables you would like defined when the jscode executes. One can think of these as "bind variables".

Examples: conn.findOne("test.coll", Query("{a:3}").where("this.b == 2 || this.c == 3")); Query badBalance = Query().where("this.debits - this.credits < 0");

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The documentation for this class was generated from the following files:

• dbclientinterface.h
• dbclient.cpp