Retry entire update (including find) excluding success docs when concurrent update detected

[alechenninger]

This would establish a true happens before relationship for concurrent update operations which are resequenced.

The effect is that for given requests A and B which interleave[1], the effects of the one that is successful are entirely visible to a retry of B. This means the operations are exactly equivalent to if A and B did not interleave, and one finished completely before the other.

[1] Where interleaved is defined as, when multiple update requests against an overlapping set of documents make finds before at least one among them has made its updates

[alechenninger]

@bserdar What if we retried the query, excluding docs with the doc version? If they have the doc version, that means it was successful, and we don't need to work with the unbounded set of _ids.

Have to be careful the doc version hasn't expired yet, and may want to index doc version by default in that case?

[bserdar]

It could be possible to implement this using an exclusion on docid. An index on docid won't be helpful for this case.