How are results ordered in solr in a “match all docs” query

Question

When I use a "match all docs" query, '*:*', asterisk colon asterisk, how are the results ordered?

I presume they get ordered by relevancy, but the relevancy is equal in this case, right? So then, what's the scheme?

Answer 1

When two documents have the same score, Lucene sorts them by index order (the first which has been indexed first) so that running a query twice returns documents in the same order.

Since MatchAllDocsQuery gives a constant score to all documents, it returns them in index order.