$concatArrays (aggregation)
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Definition
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$concatArrays
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New in version 3.2.
Concatenates arrays to return the concatenated array.
$concatArrays
has the following syntax:The
<array>
expressions can be any valid expression as long as they resolve to an array. For more information on expressions, see Expressions.If any argument resolves to a value of
null
or refers to a field that is missing,$concatArrays
returnsnull
.