There is a bug in EquivSet.tryMergeGroups, which could cause an invariant (that equiv groups are non-intersecting) to be violated. This would potentially cause re-ordered joins to have redundant equality filters, and prevent join filter push-down in rare cases. The issue (called out by @mgartner here) is that the method removes an item from the slice by replacing it with the last item while iterating forward. This results in the swapped item not being encountered by the loop.

Jira issue: CRDB-45545