On Jul 9, 2013, at 8:50 AM, Robert Newson <[email protected]> wrote:
> It's not true. Passing replication through a filter is a linear > slowdown (the cost of passing the document to spidermonkey for > evaluation), nothing more. Filtered replication is as > incremental/resumable as non-filtered replication. I’ve heard from mobile-app developers for whom this has become a scaling problem. It’s a linear slowdown, yes, but the CPU time to run the JS function is multiplied by the number of clients squared times the number of doc updates each client produces, since every client sees the updates from every other client. (That’s assuming the clients are always online and replicating. If not, multiple updates to the same doc in between replications will get coalesced, lowering the workload.) >From the n^2 factor in the number of clients, I’d guess that this is less of >an issue for a server-to-server setup where the number of database instances >isn’t too big, but gets bad when you get to thousands or hundreds of thousands >of clients. —Jens
