Re: Switching XLog source from archive to streaming when primary available

The following review has been posted through the commitfest application:
make installcheck-world:  tested, passed
Implements feature:       tested, passed
Spec compliant:           not tested
Documentation:            not tested

Hello

I tested this patch in a setup where the standby is in the middle of replicating and REDOing primary's WAL files during
avery large data insertion. During this time, I keep killing the walreceiver process to cause a stream failure and
forcestandby to read from archive. The system will restore from archive for "wal_retrieve_retry_interval" seconds
beforeit attempts to steam again. Without this patch, once the streaming is interrupted, it keeps reading from archive
untilstandby reaches the same consistent state of primary and then it will switch back to streaming again. So it seems
thatthe patch does the job as described and does bring some benefit during a very large REDO job where it will try to
re-streamafter restoring some WALs from archive to speed up this "catch up" process. But if the recovery job is not a
largeone, PG is already switching back to streaming once it hits consistent state.
 

thank you

Cary Huang
HighGo Software Canada