$addToSet¶
-
$addToSet
¶ The
$addToSet
operator adds a value to an array only if the value is not in the array already. If the value is in the array,$addToSet
returns without modifying the array. Consider the following example:Here,
$addToSet
appendsvalue1
to the array stored infield
, only ifvalue1
is not already a member of this array.Note
$addToSet
only ensures that there are no duplicate items added to the set and does not affect existing duplicate elements.$addToSet
does not guarantee a particular ordering of elements in the modified set.-
:update:`$each`
See also
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