private FieldCollection getCollection(String collectionName) {
        FieldCollection retval = collections.get(collectionName);
        if (retval == null) {
            collections.put(collectionName, new FieldCollection(collectionName));
            return collections.get(collectionName);
        }
        return retval;
    }
Deriver of indexschema config containing information of all text index fields with name and data type.

@author geirst
config-model/src/main/java/com/yahoo/schema/derived/IndexSchema.java