In MongoDB, the $sum aggregation pipeline operator calculates and returns the sum of numeric values.

In MongoDB, the $avg aggregation pipeline operator calculates and returns the average value of the specified numeric values.

In MongoDB, the $substrBytes aggregation pipeline operator returns the substring of a string, based on the specified UTF-8 encoded bytes indexes.

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

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.

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.

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.

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.

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.