Re: pg_last_xact_insert_timestamp

Thanks for all the feedback guys.  Just to throw another monkey wrench in here - I've been playing with Simon's proposed solution of returning 0 when the WAL positions match, and I've come to the realizatiion that even if using pg_last_xact_insert_timestamp, although it would help, we still wouldn't be able to get a 100% accurate "how far behind?" counter....not that this is a big deal, but I know my ops team is going to bitch to me about it :).....take this situation: there's a lull of 30 seconds where there are no transactions committed on the server....the slave is totally caught up, WAL positions match, I'm reporting 0, everything is happy.  Then a transaction is committed on the master....before the slave gets it my query hits it and sees that we're 30 seconds behind (when in reality we're <1sec behind).....Because of this affect my graph is a little spikey...I mean it's not a huge deal or anything - I can put some sanity checking in my number reporting ("if 1 second ago you were 0 seconds behind, you can't be more than 1 second behind now" sorta thing).  But if we wanted to go for super-ideal solution there would be a way to get the timestamp of pg_stat_replication.replay_location+1 (the first transaction that the slave does not have).