Would add one more 4. Write throughput degradation - For non unique property index which make use of ContentMirrorStoreStrategy we have seen a loss in throughput due to contention which arise due to conflicts while entries are made in index. (OAK-2673, OAK-3380)
Chetan Mehrotra On Fri, Aug 5, 2016 at 10:34 PM, Michael Marth <[email protected]> wrote: > Hi, > > I have noticed OAK-4638 and OAK-4412 – which both deal with particular > problematic aspects of property indexes. I realise that both issues deal with > slightly different problems and hence come to different suggested solutions. > But still I felt it would be good to take a holistic view on the different > problems with property indexes. Maybe there is a unified approach we can take. > > To my knowledge there are 3 areas where property indexes are problematic or > not ideal: > > 1. Number of nodes: Property indexes can create a large number of nodes. For > properties that are very common the number of index nodes can be almost as > large as the number of the content nodes. A large number of nodes is not > necessarily a problem in itself, but if the underlying persistence is e.g. > MongoDB then those index nodes (i.e. MongoDB documents) cause pressure on > MongoDB’s mmap architecture which in turn affects reading content nodes. > > 2. Write performance: when the persistence (i.e. MongoDB) and Oak are “far > away from each other” (i.e. high network latency or low throughput) then > synchronous property indexes affect the write throughput as they may cause > the payload to double in size. > > 3. I have no data on this one – but think it might be a topic: property index > updates usually cause commits to have / as the commit root. This results on > pressure on the root document. > > Please correct me if I got anything wrong or inaccurate in the above. > > My point is, however, that at the very least we should have clarity which one > go the items above we intend to tackle with Oak improvements. Ideally we > would have a unified approach. > (I realize that property indexes come in various flavours like unique index > or not, which makes the discussion more complex) > > my2c > Michael
