what is

In MongoDB, the $substrCP aggregation pipeline operator returns the substring of a string, based on the specified UTF-8 code point indexes.

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MongoDB, the $strLenCP aggregation pipeline operator returns the number of UTF-8 code points in the specified string.

The $strLenCP operator is different to the $strLenBytes operator, which returns the number of bytes in the string.

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MongoDB, the $strLenBytes aggregation pipeline operator returns the number of UTF-8 encoded bytes in the specified string.

Each character in a string can contain contain a different number of bytes, depending on the character being used. The $strLenBytes operator can figure out how many bytes each character contains and return the correct result for the whole string.

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In MongoDB, the $stdDevPop aggregation pipeline operator calculates the population standard deviation of its input values. 

The input values can be from a group of documents (i.e. documents that are grouped by the same key), or they can be multiple fields within a single document.

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In MongoDB, the $stdDevSamp aggregation pipeline operator calculates the sample standard deviation of the input values.

The input values can be from a group of documents (i.e. documents that are grouped by the same key), or they can be multiple fields within a single document.

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In MongoDB, the $strcasecmp aggregation pipeline operator performs a case-insensitive comparison of two strings.

It returns either 1, 0, or -1, depending on whether or not the first string is greater than, equal to, or less than the second string.

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In MongoDB, the $split aggregation pipeline operator divides a string into an array of substrings based on a delimiter.

The delimiter is removed from the string, and the substrings are added as elements to the array.

To use $split, you specify the string and the delimiter.

If the delimiter isn’t found in the string, the original string is returned as the only item in the array.

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In MongoDB, the $slice aggregation pipeline operator returns a subset of an array.

To use $slice, you specify the number of elements to return from the array. You can also specify a starting position for which to take the subset from the array.

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In MongoDB, the $size aggregation pipeline operator counts and returns the total number of items in an array.

The $size operator accepts one argument. The argument can be any valid expression that resolves to an array.

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In MongoDB, the $setUnion aggregation pipeline operator accepts two or more arrays and returns an array containing the elements that appear in any of those input arrays.

$setUnion accepts two or more arguments, all of which can be any valid expression as long as they each resolve to an array. $setUnion treats the arrays as sets.

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