On a whole fleet of load-balanced replicas, we saw an incident where one particular query started backing up on MultiXactMemberControlLock and multixact_member. There was no sign of this backup on the primary. Under what conditions would there be enough multixact members on a replica (where you can't do UPDATE / SELECT FOR UPDATE / FOR SHARE) to start spilling to disk?
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-- Christophe Pettus
xof(at)thebuild(dot)com