Interaction with Other MarkLogic Features
For existing features that will work as expected with MarkLogic 9, a rolling upgrade will not have any impact. Some existing features may not work as expected until the rolling upgrade is complete and the cluster has been committed to the newer version.
One possible example of this would be semantic triples, where the triple count may be increased after inserting same data twice in during a rolling upgrade in mixed mode. During a rolling upgrade, the MarkLogic 9 triple index is not able to return triples in the correct order for MarkLogic 8 semantics. A user would need to have multiple triples that are identical, except for the types of the values for this situation to occur.
Features introduced in MarkLogic 9 may or may not work in a mixed cluster (a cluster that has not been completely upgraded to MarkLogic 9, and has an effective version of 8.0-x).
This section describes the features that may need to be monitored while performing a rolling upgrade.