Add $min/max update modifiers which leave/replace the existing field based on the comparison of a provided value.

Note: if the field is missing then the value supplied will replace it like it was specified via a $set.

Examples:

> db.v.find()

{_id:1, v:1}

{_id:2, v:2}

{_id:3}

{_id:4}

> db.v.update({_id:1}, {$min: {v: 2}} // do not change the doc, existing value is smaller

> db.v.update({_id:1}, {$min: {v: 0}} // set v to 0

> db.v.findOne({_id:1})

{_id:1, v:0}

> db.v.update({_id:2}, {$max: {v: 1}} // do not change the doc, existing value is larger

> db.v.update({_id:2}, {$max: {v: 2}} // do not change the doc, existing value is the same

> db.v.update({_id:2}, {$max: {v: 200}} // set v to 200

> db.v.findOne({_id:2})

{_id:2, v:200}

> db.v.update({_id:3}, {$min: {v: 2}} // set v to 2

{_id:3, v:2}

> db.v.update({_id:4}, {$max: {v: 2}} // set v to 2

{_id:4, v:2}

old description
I'm working on a realtime website performance analysis tool, were a number of parallel processes import data into a mongodb instance.

In this context, it would be extremely helpful to have $max and $min update operators which would work similar to $inc.

{ $min :

}

sets field to new value if field does not exist or value is smaller than current field value.

{ $max :

}

sets field to new value if field does not exist or value is larger than current field value.