Hi, Sorry for the late reply.
On Fri, Nov 19, 2021 at 7:24 AM Melanie Plageman <melanieplage...@gmail.com> wrote: > > On Sun, Aug 22, 2021 at 9:47 PM Masahiko Sawada <sawada.m...@gmail.com> wrote: > > > > On Thu, Aug 19, 2021 at 10:52 PM Ranier Vilela <ranier...@gmail.com> wrote: > > > > > > Em qui., 19 de ago. de 2021 às 09:21, Masahiko Sawada > > > <sawada.m...@gmail.com> escreveu: > > > > > The presentation seems a little confusing, wouldn't it be better? > > > > > > I/O Timings: shared/local read=xxxx write=xxx temp read=0.487 write=2.073 > > > > Yeah, it looks better to add "shared/local". > > Using the patch, I do feel like the EXPLAIN format of > > shared/local xxx, temp xxx > > is a bit confusing. If temp is going to be its own EXPLAIN IO timing > category (as opposed to being summed with relation data block IO from > local and shared buffers), then it seems like local and shared should > be separated as well. > > shared xxx, local xxx, temp xxx I think the I/O timing shown as shared/local is the time spent on disk I/O so it doesn't matter if these disk I/O are for shared buffers or local buffers. > > With your patch applied, below is the top of the EXPLAIN output for a > query joining a temporary table (so using local buffers) to a regular > table (using shared buffers) and spilling the hash join (temp files). > > Aggregate (actual rows=1 loops=1) > Buffers: shared read=4425, local read=4425 dirtied=4425 > written=4423, temp read=5963 written=5963 > I/O Timings: shared/local read=23.546, temp read=13.309 write=74.198 > > I found that using the same terminology as the "EXPLAIN BUFFERS" output > but not using the same categories was kind of confusing. > > If it is only meaningful to distinguish between relation data IO and > query temp file IO, then maybe the words used in I/O Timings in EXPLAIN > should be "rel data" and "temp" or something like that. But if we do that, we end up using different terminology in "I/O Timing" and "Buffers". I think it's better to use consistent words used in them. Regards, -- Masahiko Sawada EDB: https://www.enterprisedb.com/