Re: seg fault crashed the postmaster

I tried to replicate the problem here without success, which suggests to
me that maybe it's plan-dependent.  Can you show what EXPLAIN gives you
for the troublesome query?

Another point here is that your logs suggest that the query blocked
behind the previous updater of the row for a very long time --- 90 sec
in one case, 30 sec in another.  Is that the typical runtime for one of
these updates?  If not, can you identify what the blocking query was?
If it's something different from another instance of the identical
update, it'd be useful to know what.