I have a question regarding the _ts field within the documentdb. How is it determined? My understanding is that when a document is added/altered it gets a new _ts. Are there any chance that two documents have the same _ts? If so, does it happen only if those documents are added at the exact time (in terms of milli second).
Answer
_ts is a system property denoting when a document was last updated (e.g. create or replace).
_ts is represented as a POSIX or epoch time value. In other words, its the number of seconds (not milliseconds) that have elapsed since 00:00:00 (UTC), 1 January 1970.
It is possible to have the same _ts value across multiple documents when there are multiple documents written/updated during the same second.