Use custom collation to specify language-specific rules for string comparison, such as rules for letter case and accent marks, within your aggregation pipeline.
About this Task
When entering a collation document, the locale field is mandatory. Default collation field values vary depending on which locale you specify. To learn more about supported languages and locales, see Collation Locales and Default Parameters.
Steps
Enter your collation document
Next to the Collation field, enter your collation document.
After you enter your collation document, the aggregation pipeline builder considers the language-specific rules that you specified in your document.
Example
The following sample collation document specifies French as the chosen locale and sorts uppercase letters before lowercase letters with the caseFirst field:
{
locale: "fr",
caseFirst: "upper"
}