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PostgreSQL replication delay/lag

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I think the best one would be 2 combined with a check if the wal receiver process is running before running that
query with something like:

$ ps aux | egrep 'wal\sreceiver'
postgres  3858  0.0  0.0 2100112 3312 ?        Ss   19:35   0:01 postgres:
wal receiver process   streaming 36/900A738
This solution would only be run on the slave and it is pretty easy to setup.

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