On Tue, Jul 10, 2018 at 8:33 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Asim R P <aprav...@pivotal.io> writes: > >> One can find several PageInit() calls with no content lock held. See, >> for example: > >> fill_seq_with_data() > > That would be for a relation that no one else can even see yet, no?
Yes, when the sequence is being created. No, when the sequence is being reset, in ResetSequence(). > >> vm_readbuf() >> fsm_readbuf() > > In these cases I'd imagine that the I/O completion interlock is what > is preventing other backends from accessing the buffer. > What is I/O completion interlock? I see no difference in initializing a visimap/fsm page and initializing a standard heap page. For standard heap pages, the code currently acquires the buffer pin as well as content lock for initialization. >> Moreover, fsm_vacuum_page() performs >> "PageGetContents(page))->fp_next_slot = 0;" without content lock. > > That field is just a hint, IIRC, and the possibility of a torn read > is explicitly not worried about. Yes, that's a hint. And ignoring torn page possibility doesn't result in checksum failures because fsm_read() passes RMB_ZERO_ON_ERROR to buffer manager. The page will be zeroed out in the event of checksum failure. Asim