presto-main/src/main/java/io/prestosql/operator/scalar/StringFunctions.java/StringFunctions/charLeftTrim
class StringFunctions:    @Description("removes whitespace from the beginning of a string")
    @ScalarFunction("ltrim")
    @LiteralParameters("x")
    @SqlType("char(x)")
    public static Slice charLeftTrim(@SqlType("char(x)") Slice slice)
    {
        return SliceUtf8.leftTrim(slice);
    }