MongoDB request DSL • opensavvy.ktmongo.dsl.aggregation.operators • StringValueOperators • length
length¶
Returns the number of code points in the specified string.
If the argument resolves to null, this function returns null.
Counting characters¶
This function uses MongoDB's $strLenCP operator, which counts characters using Unicode code points. This differs from Kotlin's String.length, which uses UTF-16 code units. For strings containing characters outside the Basic Multilingual Plane (like emoji or certain mathematical symbols), the counting behavior will differ.
For example, the emoji "👨👩👧👦" (family) is a single Unicode grapheme cluster but consists of multiple code points. According to this operator, it has a length of 7. However, according to Kotlin's String.length, it has a length of 11.
Example¶
class Document(
val text: String,
val length: Int,
)
collection.aggregate()
.set {
Document::length set of(Document::text).length
}.toList()