aggregation

In MongoDB, the $lt aggregation pipeline operator compares two values and returns either true or false, depending on whether or not the first value is less than the second value.

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In MongoDB, the $filter aggregation pipeline operator returns a subset of an array based on a specified condition.

The $filter operator returns an array with only those elements that match the condition, in their original order.

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In MongoDB, the $exp aggregation pipeline operator raises Euler’s number (i.e. e ) to the specified exponent and returns the result.

The exponent can be any valid expression that resolves to a number.

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In MongoDB, the $tanh aggregation pipeline operator returns the hyperbolic tangent of a value that is measured in radians.

$tanh accepts any valid expression that resolves to a number.

The $tanh operator was introduced in MongoDB 4.2.

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In MongoDB, the $eq aggregation pipeline operator compares two values and returns either true or false, depending on whether the two values are equivalent or not.

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In MongoDB, the $cond aggregation pipeline operator evaluates a boolean expression, and returns one of the two specified return expressions, depending on whether the boolean expression is true or false.

The $cond operator accepts two syntaxes: a longhand syntax and a shorthand syntax. Examples of each are below.

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In MongoDB, the $concat aggregation pipeline operator concatenates two or more strings and returns the concatenated string.

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In MongoDB, the $cmp aggregation pipeline operator compares two values and returns either -1, 1, or 0, depending on whether the first value is less than, greater than, or equal to the first value.

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In MongoDB, the $floor aggregation pipeline operator returns the largest integer less than or equal to the specified number.

$floor accepts any valid expression that resolves to a number.

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