On 10/22/15 5:11 PM, Robert Haas wrote:
It's true that if the standby didn't have the master's FPIs, it could generate its own in some side location that behaves like a separate WAL stream or a double-write buffer. But that would be a heck of a lot of work to implement for an uncertain benefit.
If the receiver didn't write the WAL before processing it then it can just stick the page image into the WAL it's writing for itself. Probably not good for syncrep, but I don't think you'd want this on for syncrep anyway.
But yes, this is all very hand-wavy without any actual data on what percentage of the WAL stream is FPIs. Looks like pageinspect doesn't work for WAL... does anyone have a script/tool that breaks out what percentage of a WAL file is FPIs?
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