The Unicode Collation Algorithm
(UCA) is a specification (Unicode Technical Report #10
) that defines a customizable method of collating and comparing Unicode data. Collation
means how data is sorted as with a SELECT … ORDER BY
is relevant for searches that use ranges with less than, greater than, or equal to operators.
In addition, another advantage for using ICU collations (the implementation of the Unicode Collation Algorithm) is for performance. Sorting tasks, including B-tree index creation, can complete in less than half the time it takes with a non-ICU collation. The exact performance gain depends on your operating system version, the language of your text data, and other factors.