mongo::Query Class Reference

Represents a Mongo query expression. More...

#include <dbclientinterface.h>

Public Member Functions
Query &	sort (const BSONObj &sortPattern)
	Add a sort (ORDER BY) criteria to the query expression.
Query &	sort (const std::string &field, int asc=1)
	Add a sort (ORDER BY) criteria to the query expression.
Query &	hint (BSONObj keyPattern)
	Provide a hint to the query.
Query &	maxTimeMs (int millis)
	Specifies a cumulative time limit in milliseconds for processing an operation.
Query &	minKey (const BSONObj &val)
	Provide min and/or max index limits for the query.
Query &	maxKey (const BSONObj &val)
	max is exclusive
Query &	explain ()
	Return explain information about execution of this query instead of the actual query results.
Query &	snapshot ()
	Use snapshot mode for the query.
Query &	where (const std::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.
Query &	readPref (ReadPreference pref, const BSONArray &tags)
	Sets the read preference for this query.
bool	isComplex (bool *hasDollar=0) const

Static Public Member Functions
static bool MONGO_CLIENT_FUNC	hasReadPreference (const BSONObj &queryObj)

Detailed Description

Represents a Mongo query expression.

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

Member Function Documentation

explain()

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().

hasReadPreference()

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

static

Returns

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

hint()

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}")

isComplex()

bool mongo::Query::isComplex

(

bool *

hasDollar = 0

)

const

Returns

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

maxTimeMs()

Query & mongo::Query::maxTimeMs

(

int

millis

)

Specifies a cumulative time limit in milliseconds for processing an operation.

MongoDB will interrupt the operation at the earliest following interrupt point.

minKey()

Query & mongo::Query::minKey

(

const BSONObj &

val

)

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

min <= x < max

readPref()

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.

snapshot()

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.

sort() [1/2]

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 ")

sort() [2/2]

Query & mongo::Query::sort ( const std::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

where()

Query & mongo::Query::where	(	const std::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 file:

• src/mongo/client/dbclientinterface.h