On Wed, May 14, 2014 at 12:02 AM, Gilles Dubuc gilles@wikimedia.org wrote:
Ops can add indexes to the EventLogging tables for us, SQL queries grouping by that column should pose no challenge.
As far as I can see, this can't be done with a simple GROUP BY: you would need logic like "from all records with the same sequence id which have an authorship_change field set, select the one with the latest timestamp". In SQL dialects supporting windowed/analytical expressions this is not bad, but in MySQL it would require some sort of self-join, I think.