Sorry to reply to myself but here's a bit more info. That strace shows
a crash. The node that was denying logins is now complaining about
checkpoint file 000...000. It appears to be the case that a few
attempts to start converts a db that rejects logins to one that
crashes on startup. (When I first started examining the damage, I was
able to start all four dbs but not login.)
Morris
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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
