$min
Definition
Deprecated since v3.2
Starting in v3.2, the $min
operator is deprecated in themongo
shell. In the mongo
shell,use cursor.min()
instead.
Specify a $min
value to specify the inclusive lowerbound for a specific index in order to constrain the results offind()
. The $min
specifies thelower bound for all keys of a specific index in order.
The mongo
shell provides the min()
wrapper method:
- db.collection.find( { <query> } ).min( { field1: <min value>, ... fieldN: <min valueN>} )
You can also specify the option with either of the two forms:
- db.collection.find( { <query> } )._addSpecial( "$min", { field1: <min value1>, ... fieldN: <min valueN> } )
- db.collection.find( { $query: { <query> }, $min: { field1: <min value1>, ... fieldN: <min valueN> } } )
Behavior
Interaction with Index Selection
Because min()
requires an index on a field, andforces the query to use this index, you may prefer the$gte
operator for the query if possible. Consider thefollowing example:
- db.collection.find( { _id: { $in: [ 6, 7 ] } } ).min( { age: 25 } ).hint( { age: 1 } )
The query will use the index on the age
field, even if theindex on _id
may be better.
Index Bounds
If you use $max
with $min
to specify a range,
the index bounds specified in
$min
and$max
must both refer to the keys of the same index.the bound specified by
$max
must be greater thanthe bound specified by$min
.
Changed in version 4.0.
$min without $max
The min
and max
operators indicate that the systemshould avoid normal query planning. Instead they construct an index scan wherethe index bounds are explicitly specified by the values given inmin
and max
.
Warning
If one of the two boundaries is not specified, the query plan will bean index scan that is unbounded on one side. This may degrade performancecompared to a query containing neither operator, or one that uses bothoperators to more tightly constrain the index scan.
Examples
The following examples use the mongo
shell wrappers.
Specify Inclusive Lower Bound
Consider the following operations on a collection namedcollection
that has an index { age: 1 }
:
- db.collection.find().min( { age: 20 } ).hint( { age: 1 } )
This operation limits the query to those documents where thefield age
is at least 20
and forces a query plan which scans the{ age: 1 }
index from 20 to MaxKey.
Use with $max
You can use $min
in conjunction with $max
tolimit results to a specific range for the same index, as in thefollowing example:
Note
Changed in version 4.0: The bound specified by $max
must be greater than thebound specified by $min
.
- db.collection.find().min( { age: 20 } ).max( { age: 25 } ).hint( { age: 1 } )