Hello! I'm wondering what information you may be able to provide on performance implications of implicit routing VS composite ID routing. In particular, I'm curious what the horizontal scaling behavior may be of implicit routing or composite ID routing with and without the "/<bits>" param appended on.
I've been following this documentation <https://lucene.apache.org/solr/guide/6_6/shards-and-indexing-data-in-solrcloud.html>, and a few other blogs/articles I've seen around the web (including on lucid works). Many of these discuss what the techniques and general philosophy are of different document routing techniques, but I haven't been able to find a "Big O" assessment so far by searching online. I'm aware than any particular workload really needs a Sizing Exercise <https://lucidworks.com/blog/2012/07/23/sizing-hardware-in-the-abstract-why-we-dont-have-a-definitive-answer/> to fully understand its implications, but I'm hoping to plan high level architecture beyond what I can currently forsee in scale. A relatively simple assessment I've done belowleads me to believe the following is likely the case: if we have S shards and B as our "/bits" param, then resource usage would Big O scale as follows (note: Previously I've received the advice that any shard should be capped at a max of 120M documents, which is where the cap on docs/shard-key comes from) - Implicit routing - One Read: O(S) - hits horizontal scaling limit eventually as S grows - No cap on docs per shard key (no shard key) - Composite ID routing, no bits param: - One Read: O(1) - no horizontal scaling limit as S grows - Docs on a shard key capped at 120 million - Composite ID routing with bits param: - One Read: O(2^B) - no horizontal scaling limit as S grows for fixed B - Docs on a shard key capped at 120 million * 2^B So my questions: Is this "big O" analysis about correct? Does SOLR have an ability to scale horizontally on implicit routing despite what my simple analysis would suggest? Are there other considerations here you can enlighten me on? I would guess the answer to the second question is "no" because otherwise it wouldn't seem to me that composite ID routing would add much concrete value. But perhaps there are some other factors I've yet to consider. Thanks for your time and help! Looking forward to hearing back :) Cheers, Stephen