On Tue, Jan 23, 2018 at 08:49:53PM +0100, Laurenz Albe wrote: > When a primary with replication slots gets reset with pg_rewind, > it keeps the replication slots. > > This does no harm per se, but when it gets promoted again, > the replication slots are still there and are in the way. > Won't they also hold back the xmin horizon? > > I think that pg_rewind should delete all replication slots.
Definitely agreed, but replications slots are not the only thing to worry about. There has been a recent discussion on the matter: https://www.postgresql.org/message-id/20180122201258.gt2...@tamriel.snowman.net And the conclusion leads to the fact that we want the list of directories and files that should be excluded from a base backup to extracted into a header that pg_rewind could use for its own purpose as it shares a lot in its logic with basebackup.c, and because using a logic based on an exclusion list is more portable in the long run. (I do remove pg_replslot's contents after running pg_rewind in my own failover scripts by the way.) -- Michael
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