cursor.min()

Definition

  • cursor.min()

mongo Shell Method

This page documents the mongo shell method, and doesnot refer to the MongoDB Node.js driver (or any other driver)method. For corresponding MongoDB driver API, refer to your specificMongoDB driver documentation instead.

Specifies the inclusive lower bound for a specific index in orderto constrain the results offind(). min() provides away to specify lower bounds on compound key indexes.

The min() method has the following parameter:

ParameterTypeDescriptionindexBoundsdocumentThe inclusive lower bound for the index keys.

The indexBounds parameter has the following prototype form:

  1. { field1: <min value>, field2: <min value2>, fieldN:<min valueN> }

See also

max().

min() exists primarily to support themongos process, and is a shell wrapper around thequery modifier $min.

Deprecated since v3.2

Starting in v3.2, the $min operator is deprecated in themongo shell. In the mongo shell,use cursor.min() instead.

Behaviors

Interaction with Index Selection

Because min() requires an index on afield, and forces the query to use this index, you may preferthe $gte operator for the query ifpossible. Consider the following example:

  1. db.products.find( { $in: [ 6, 7 ] } ).min( { price: NumberDecimal("1.39") } ).hint( { price: 1 })

The query will use the index on the price field, even ifthe index on _id may be better.

Index Bounds

If you use min() with max() tospecify a range:

  • the index bounds specified in min() andmax() 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.

Example

Starting in MongoDB 4.2, you must explicitly specify the particularindex with the hint() method to runmin() with the following exception: you do notneed to hint if the find() query is anequality condition on the _id field { _id: <value> }.

For the examples below, create a sample collection named products that holds thefollowing documents:

  1. db.products.insertMany([
  2.    { "_id" : 1, "item" : "apple", "type" : "honey crisp", "price" : NumberDecimal("1.99") },
  3.    { "_id" : 2, "item" : "apple", "type" : "fuji", "price" : NumberDecimal("1.99") },
  4.    { "_id" : 3, "item" : "apple", "type" : "jonagold", "price" : NumberDecimal("1.29") },
  5.    { "_id" : 4, "item" : "apple", "type" : "jonathan", "price" : NumberDecimal("1.29") },
  6.    { "_id" : 5, "item" : "apple", "type" : "mcintosh", "price" : NumberDecimal("1.29") },
  7.    { "_id" : 6, "item" : "apple", "type" : "cortland", "price" : NumberDecimal("1.29") },
  8.    { "_id" : 7, "item" : "orange", "type" : "cara cara", "price" : NumberDecimal("2.99") },
  9.    { "_id" : 9, "item" : "orange", "type" : "satsuma", "price" : NumberDecimal("1.99") },
  10.    { "_id" : 8, "item" : "orange", "type" : "valencia", "price" : NumberDecimal("0.99") },
  11.    { "_id" : 10, "item" : "orange", "type" : "navel", "price" : NumberDecimal("1.39") }
  12. ])

Create the following indexes for the collection:

  1. db.products.createIndexes( [
  2.    { "item" : 1, "type" : 1 },
  3.    { "item" : 1, "type" : -1 },
  4.    { "price" : 1 }
  5. ] )
  • Using the ordering of the { item: 1, type: 1 } index,min() limits the query to the documentsthat are at or above the index key bound of item equal toapple and type equal to jonagold, as in the following:
  1. db.products.find().min( { item: 'apple', type: 'jonagold' } ).hint( { item: 1, type: 1 } )

The query returns the following documents:

  1. { "_id" : 3, "item" : "apple", "type" : "jonagold", "price" : NumberDecimal("1.29") }
  2. { "_id" : 4, "item" : "apple", "type" : "jonathan", "price" : NumberDecimal("1.29") }
  3. { "_id" : 5, "item" : "apple", "type" : "mcintosh", "price" : NumberDecimal("1.29") }
  4. { "_id" : 7, "item" : "orange", "type" : "cara cara", "price" : NumberDecimal("2.99") }
  5. { "_id" : 10, "item" : "orange", "type" : "navel", "price" : NumberDecimal("1.39") }
  6. { "_id" : 9, "item" : "orange", "type" : "satsuma", "price" : NumberDecimal("1.99") }
  7. { "_id" : 8, "item" : "orange", "type" : "valencia", "price" : NumberDecimal("0.99") }
  • Using the ordering of the index { price: 1 }, min() limits the query to the documents that are at orabove the index key bound of price equal to 1.39 andmax() limits the query to the documentsthat are below the index key bound of price equal to 1.99:

Note

Changed in version 4.0: The bound specified by max() must be greaterthan the bound specified by min().

  1. db.products.find().min( { price: NumberDecimal("1.39") } ).max( { price:  NumberDecimal("1.99") } ).hint( { price: 1 } )

The query returns the following documents:

  1. { "_id" : 10, "item" : "orange", "type" : "navel", "price" : NumberDecimal("1.39") }