SolrFields.SOLR_COLLECTION vs SolrFields.COLLECTION, same string value

[vkush]

Investigating issue #315 I have found, that variables "SOLR_COLLECTION" and "COLLECTION" represent the same property "collection":

webarchive-discovery/warc-indexer/src/main/java/uk/bl/wa/solr/SolrFields.java

Line 67 in 13595be

public static final String SOLR_COLLECTION = "collection"; // Top-level collection

and

webarchive-discovery/warc-indexer/src/main/java/uk/bl/wa/solr/SolrFields.java

Line 153 in 13595be

public static final String COLLECTION = "collection";

Is it correct so? Maybe yes, because I see, that variable SolrField.SOLR_COLLECTION is currently used only in one place in Annotator.java:
https://github.com/search?q=repo%3Aukwa%2Fwebarchive-discovery%20SOLR_COLLECTION&type=code
And SolrField.COLLECTION is used here:
https://github.com/search?q=repo%3Aukwa%2Fwebarchive-discovery+SolrFields.COLLECTION&type=code