On Tue, Feb 5, 2019 at 12:14 PM Haribabu Kommi <kommi.haribabu@gmail.com> wrote: > > > On Fri, Feb 1, 2019 at 8:19 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote: >> >> >> The passing stats = NULL to amvacuumcleanup and ambulkdelete means the >> first time execution. For example, btvacuumcleanup skips cleanup if >> it's not NULL.In the normal vacuum we pass NULL to ambulkdelete or >> amvacuumcleanup when the first time calling. And they store the result >> stats to the memory allocated int the local memory. Therefore in the >> parallel vacuum I think that both worker and leader need to move it to >> the shared memory and mark it as updated as different worker could >> vacuum different indexes at the next time. > > > OK, understood the point. But for btbulkdelete whenever the stats are NULL, > it allocates the memory. So I don't see a problem with it. > > The only problem is with btvacuumcleanup, when there are no dead tuples > present in the table, the btbulkdelete is not called and directly the btvacuumcleanup > is called at the end of vacuum, in that scenario, there is code flow difference > based on the stats. so why can't we use the deadtuples number to differentiate > instead of adding another flag?
I don't understand your suggestion. What do we compare deadtuples number to? Could you elaborate on that please?
The scenario where the stats should pass NULL to btvacuumcleanup function is
when there no dead tuples, I just think that we may use that deadtuples structure
to find out whether stats should pass NULL or not while avoiding the extra
memcpy.
> And also this scenario is not very often, so avoiding > memcpy for normal operations would be better. It may be a small gain, just > thought of it. >
This scenario could happen periodically on an insert-only table. Additional memcpy is executed once per indexes in a vacuuming but I agree that the avoiding memcpy would be good.
Yes, understood. If possible removing the need of memcpy would be good.
The latest patch doesn't apply anymore. Needs a rebase.