Another performance improvement could be accomplished in the latest devel-branch: The handling of large IN-lists. Those become much faster than in the previous releases. Large IN-lists are normally used when comparing attribute or index values against some big array of lookup values or keys provided by the application.
Read on how this improvement reduces query execution time.
What’s the algorithm in particular that enabled this performance increase?
Are there known limitations, like quadratic runtime again if you use two IN-list criteria in a FILTER statement, or combine one with another condition?