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cursor.min()

Definition

cursor.min()

Important

mongosh Method

This page documents a mongosh method. This is not the documentation for a language-specific driver such as Node.js.

For MongoDB API drivers, refer to the language-specific :driver:`MongoDB driver documentation </>`.

For the legacy mongo shell documentation, refer to the documentation for the corresponding MongoDB Server release:

• :v4.4:`mongo shell v4.4 </mongo>`
• mongo shell v4.2

Specifies the inclusive lower bound for a specific index in order to constrain the results of find(). min() provides a way to specify lower bounds on compound key indexes.

The min() method has the following parameter:

Parameter	Type	Description
indexBounds	document	The inclusive lower bound for the index keys.

The indexBounds parameter has the following prototype form:

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

Note

Index Use

Starting in MongoDB 4.2, you must explicitly specify the particular index with the hint() method to run min() with the following exception: you do not need to hint if the find() query is an equality condition on the _id field { _id: <value> }.

In previous versions, you could run min() with or without explicitly hinting the index. If run without the hint in 4.0 and earlier, MongoDB selects the index using the fields in the indexBounds; however, if multiple indexes exist on same fields with different sort orders, the selection of the index may be ambiguous.

See also

max()

min() exists primarily to support the mongos process.

Behaviors

Interaction with Index Selection

Because min() requires an index on a field, and forces the query to use this index, you may prefer the $gte operator for the query if possible. Consider the following example:

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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 if the index on _id may be better.

Index Bounds

If you use min() with max() 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 than the bound specified by min().

  Changed in version 4.0.

min() without max()

The min() and max() methods indicate that the system should avoid normal query planning. They construct an index scan where the index bounds are explicitly specified by the values given in min() and max().

Warning

If one of the two boundaries is not specified, the query plan will be an index scan that is unbounded on one side. This may degrade performance compared to a query containing neither operator, or one that uses both operators to more tightly constrain the index scan.

Example

Starting in MongoDB 4.2, you must explicitly specify the particular index with the hint() method to run min() with the following exception: you do not need to hint if the find() query is an equality condition on the _id field { _id: <value> }.

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

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

Create the following indexes for the collection:

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db.products.createIndexes( [
   { "item" : 1, "type" : 1 },
   { "item" : 1, "type" : -1 },
   { "price" : 1 }
] )

• Using the ordering of the { item: 1, type: 1 } index, min() limits the query to the documents that are at or above the index key bound of item equal to apple and type equal to jonagold, as in the following:

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  db.products.find().min( { item: 'apple', type: 'jonagold' } ).hint( { item: 1, type: 1 } )
  

  The query returns the following documents:

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  { "_id" : 3, "item" : "apple", "type" : "jonagold", "price" : NumberDecimal("1.29") }
  { "_id" : 4, "item" : "apple", "type" : "jonathan", "price" : NumberDecimal("1.29") }
  { "_id" : 5, "item" : "apple", "type" : "mcintosh", "price" : NumberDecimal("1.29") }
  { "_id" : 7, "item" : "orange", "type" : "cara cara", "price" : NumberDecimal("2.99") }
  { "_id" : 10, "item" : "orange", "type" : "navel", "price" : NumberDecimal("1.39") }
  { "_id" : 9, "item" : "orange", "type" : "satsuma", "price" : NumberDecimal("1.99") }
  { "_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 or above the index key bound of price equal to 1.39 and max() limits the query to the documents that are below the index key bound of price equal to 1.99:

  Note

  Starting in MongoDB 4.0, the bound specified by max() must be greater than the bound specified by min().

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

  The query returns the following documents:

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

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