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?

Arcuation

The relevancy is 1.0 for all documents; the result from a *:* query on my solr instance starts with words containing Ek... It's definitely not ordering on my id or uid fields, nor any other of the fields; perhaps on some sorted list of n-grams? – Samantha

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.

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