On Mon, Sep 16, 2019 at 9:30 AM Robert Haas <robertmh...@gmail.com> wrote: > > Isn't some operations where at the end we directly call heap_sync > > without writing WAL will have a similar problem as well? > > Maybe. Can you give an example?
Looking through the code, I found two cases where we do this. One is a bulk insert operation with wal_level = minimal, and the other is CLUSTER or VACUUM FULL with wal_level = minimal. In both of these cases we are generating new blocks whose LSNs will be 0/0. So, I think we need a rule that if the server is asked to back up all blocks in a file with LSNs > some threshold LSN, it must also include any blocks whose LSN is 0/0. Those blocks are either uninitialized or are populated without WAL logging, so they always need to be copied. Outside of unlogged and temporary tables, I don't know of any case where make a critical modification to an already-existing block without bumping the LSN. I hope there is no such case. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
