$min (original) (raw)

$min

The $min updates the value of the field to a specified value if the specified value is less than the current value of the field. The $min operator can compare values of different types, using the BSON comparison order.


{ $min: { <field1>: <value1>, ... } }

To specify a <field> in an embedded document or in an array, usedot notation.

Starting in MongoDB 5.0, update operators process document fields with string-based names in lexicographic order. Fields with numeric names are processed in numeric order. See Update Operators Behavior for details.

If the field does not exist, the $min operator sets the field to the specified value.

For comparisons between values of different types, such as a number and a null, $min uses the BSON comparison order.

Starting in MongoDB 5.0, mongod no longer raises an error when you use an update operator like $minwith an empty operand expression ( { } ). An empty update results in no changes and no oplog entry is created (meaning that the operation is a no-op).

Create the scores collection:


db.scores.insertOne( { _id: 1, highScore: 800, lowScore: 200 } )

The lowScore for the document currently has the value200. The following operation uses $min to compare200 to the specified value 150 and updates the value oflowScore to 150 since 150 is less than 200:


db.scores.updateOne( { _id: 1 }, { $min: { lowScore: 150 } } )

The scores collection now contains the following modified document:


{ _id: 1, highScore: 800, lowScore: 150 }

The next operation has no effect since the current value of the field lowScore, i.e 150, is less than 250:


db.scores.updateOne( { _id: 1 }, { $min: { lowScore: 250 } } )

The document remains unchanged in the scores collection:


{ _id: 1, highScore: 800, lowScore: 150 }

Create the tags collection:


db.tags.insertOne(

   {

     _id: 1,

     desc: "crafts",

     dateEntered: ISODate("2013-10-01T05:00:00Z"),

     dateExpired: ISODate("2013-10-01T16:38:16Z")

   }

)

The following operation compares the current value of thedateEntered field, i.e. ISODate("2013-10-01T05:00:00Z"), with the specified date new Date("2013-09-25") to determine whether to update the field:


db.tags.updateOne(

   { _id: 1 },

   { $min: { dateEntered: new Date("2013-09-25") } }

)

The operation updates the dateEntered field:


{

  _id: 1,

  desc: "crafts",

  dateEntered: ISODate("2013-09-25T00:00:00Z"),

  dateExpired: ISODate("2013-10-01T16:38:16Z")

}