Hi, This is Dharma from Azure Cosmos DB team. We are super excited to make the service available today.We published the first of the series of technical blog posts here -> https://azure.microsoft.com/en-us/blog/a-technical-overview-.... Would love to answer any Cosmos DB questions.
Are graph ops/queries atomic? i.e. if you run a tree query on a tree-graph, at the same time you're re-parenting a treenode, is there a chance that the node could end up in the result tree twice or zero times?
Also, if they're atomic, are they optimistic or pessimistic transactions? Also if they're atomic, does that mean queries done on the write server? (My understanding is that readonly transactions on read-replicas are not supported, or at least they weren't under DocDB).
Any lay-programmer insight into what's going on under the hood, or at least performance/atomicity implications, without giving up too much proprietary info, would be appreciated.
Read only transactions existed in DocumentDB too. DocumentDB was a strict subset of the capabilities that Cosmos DB provides/existed underneath. Hence, read only transactions exist in Cosmos DB too. The first technical overview blog post attempted to provide you a high level overview. We are hoping to cover specific areas in either future blog posts, conference publications.
There are many significant differences in capabilities, and design approaches between other systems and Cosmos DB. At a very high level. differences are at two levels - the design of the database engine and the larger distributed system. The database engine design is inspired on LLAMA http://db.disi.unitn.eu/pages/VLDBProgram/pdf/research/p853-..., Bwtree - > https://pdfs.semanticscholar.org/7655/9c6cc259c6ab5baf7bd19d... and schema-agnostic indexing techniques -> http://www.vldb.org/pvldb/vol8/p1668-shukla.pdf. Please note that these papers are significantly behind the current state of the implementation. The most crucial aspect that these papers dont cover is the integration of the database engine with the larger distributed system components of Cosmos DB including the resource governance, partition management, and the implementation of replication protocol /consistency models etc. Our goal is to publish all of the design specifications including TLA+ specs over time.
