Sorting fails in certain cases due to wrong fieldtype in schema.xml

[michaelkubina]

Description

The sorting feature has a fundamental issue, due to the wrong field type specified in the copyfield directive for the field "*_sorting". This causes unexpected and seemingly irrational behaviour of the sorting form or the order of the resultset respectivly.

As long as a metadata is just a single token or value, the sorting works as expecte. As soon as it consists of more than one token it fails to sort properly.

According to the SOLR-Documentation sortable fields are "score", not multivalued, single tokens (likewise analyzed with the keywordTokenizer), from a function or fundamental fieldtypes like string, int, bool. (https://solr.apache.org/guide/8_11/common-query-parameters.html#sort-parameter). Sorting does not work properly, when it's an analyzed field.

In the schema.xml the copyfield uses the "standard" fieldtype, that has its whole analyzerchain:
<dynamicField name="*_sorting" type="standard" stored="true" indexed="true" multiValued="false" />
When it actually should be a string:
<dynamicField name="*_sorting" type="string" stored="true" indexed="true" multiValued="false" />

Changing this would lead to the necessity of creating a fresh core and re-indexing all documents into it. Otherwise SOLR would log errors because of missmatching fieldtypes.