Re: [HACKERS] EXPLAIN (ANALYZE, BUFFERS) reports bogus temporary buffer reads

2017-10-31 Thread Robert Haas
On Tue, Oct 17, 2017 at 2:29 AM, Thomas Munro wrote: > Vik Fearing asked off-list why hash joins appear to read slightly more > temporary data than they write. The reason is that we notch up a > phantom block read when we hit the end of each file. Harmless but it

[HACKERS] EXPLAIN (ANALYZE, BUFFERS) reports bogus temporary buffer reads

2017-10-16 Thread Thomas Munro
Hi hackers, Vik Fearing asked off-list why hash joins appear to read slightly more temporary data than they write. The reason is that we notch up a phantom block read when we hit the end of each file. Harmless but it looks a bit weird and it's easily fixed. Unpatched, a 16 batch hash join