Projection/Stream questions

EventStoreDB
1

Hi all.

Recently I have moved the data from a single ES 2.0 instance to a ES 3.9.3 cluster. I did this using the hot swap method. The data is replicated to each node and they all reach the same checkpoint in the cluster status page, however, I believe due to a previously failed recovery (in the 2.0 instance) the $streams projections faults with the “an event emitted in recovery differs from the originally emitted event” error.

To get around it I reset the $streams projection. It is currently processing and appears to be recovering nicely, but I have some questions.

  1. Could resetting this projection have bad implications on the other system projections ($by_category, $by_event_type, $stream_by_category)?
  2. Should I also reset the other system projections? What seems unusual to me is that they are all 100% done, but they only say 1 for “Processed”. Since I have 15m events, I expected them to have a much larger number in this column. Am I mistaken? Perhaps a reset would fix that as well?

Any refs to documentation or conversations on the system projections and on the implications of resets would be much appreciated!

Thanks ahead!

Corey

2
  1. The projections you are referring to are independent of each other. Resetting one, does not effect the other.
  2. “Processed” is actually named incorrectly and the actual definition of the indicator is “EventsProcessedAfterRestart” which means that you will only see the number of events processed after Event Store has started from the most recent checkpoint.
3

Great explanations! Thanks Pieter!