Hi While reading the IndexConfig section in the Solr ref guide, I noticed that mergeFactor is exposed as its own <mergeFactor> element, and not a merge policy parameter, e.g. <int name="mergeFactor">10</int>. I think that's wrong because:
1) The merge factor only applies to our existing merge policies. I.e. if someone registers a custom merge policy which looks at other parameters but does not care about segment sizes at the same level, this parameter is useless. 2) SolrIndexConfig has redundant code if the default MP is used (TieredMP), it sets segsPerTier to mergeFactor. 3) And if the user defines both mergeFactor and segsPerTier, then the second one wins (by current code). But I think this should just be a merge policy setting, and if you are using TieredMP, you should use the settings that come with it, i.e segsPerTier and not have a weird mapping from mergeFactor to it. In terms of backwards compatibility, we can declare the standalone element deprecated, continue to respect it in 4.x and remove it in 5.0. Before I open an issue to address it, I wanted to make sure though that there isn't a good reason for why it is like that today.. Shai
