Not able to perform case insensitive sorting with SortableTextField

[Ritesh Kumar]

Hello Team,

I am facing a problem with sorting on a field with type as mentioned below

<fieldType name="*string_ci*" class="solr.SortableTextField"
positionIncrementGap="100">
        <analyzer>
            <tokenizer class="solr.KeywordTokenizerFactory"/>
            <filter class="solr.LowerCaseFilterFactory"/>
        </analyzer>
</fieldType>

<field name="fieldName" type="*string_ci*" indexed="true" stored="true"
required="false" multiValued="false">

The field may contain numerical as well as alphabetical values. My
Solr version is 7.5.0.

If I sort by "fieldName desc", this field sorts lowercase values first,
followed by Uppercase and then the digits.

I want to be able to sort values irrespective of the case and also I don't
want to change the class of the field (SortableTextField) as this type will
also be used to perform a case-insensitive search on this very field which
is working fine.

I supposed, LowerCaseFilterFactory was enough for this scenario. Is there
anything I am missing here?

Best,
Ritesh Kumar