"David G. Johnston" <david.g.johnston@xxxxxxxxx> writes: > On Monday, December 20, 2021, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: >> It would help if somebody had labeled the units of I/O Time >> ... but I'm guessing those are microsec vs. the millisec >> of the other times, because otherwise it's completely wrong. > Related to my preceding observation, from the explain (buffers) docs: > “…and the time spent reading and writing data file blocks (in milliseconds) > if track_io_timing > <https://www.postgresql.org/docs/current/runtime-config-statistics.html#GUC-TRACK-IO-TIMING> > is enabled.“ Hmm ... the code sure looks like it's supposed to be millisec: appendStringInfoString(es->str, "I/O Timings:"); if (!INSTR_TIME_IS_ZERO(usage->blk_read_time)) appendStringInfo(es->str, " read=%0.3f", INSTR_TIME_GET_MILLISEC(usage->blk_read_time)); if (!INSTR_TIME_IS_ZERO(usage->blk_write_time)) appendStringInfo(es->str, " write=%0.3f", INSTR_TIME_GET_MILLISEC(usage->blk_write_time)); And when I try some cases here, I get I/O timing numbers that are consistent with the overall time reported by EXPLAIN, for example Seq Scan on foo (cost=0.00..843334.10 rows=11000010 width=508) (actual time=0. 015..1897.492 rows=11000000 loops=1) Buffers: shared hit=15874 read=717460 I/O Timings: read=1184.638 Planning: Buffers: shared hit=5 read=2 I/O Timings: read=0.025 Planning Time: 0.229 ms Execution Time: 2151.529 ms So now we have a real mystery about what is happening on Lars' system. Those numbers can't be right. regards, tom lane
