Re: [PERFORM] Help with tuning this query (with
Tom Lane <[email protected]>
| Newsgroups | gmane.comp.db.postgresql.devel.win32,gmane.comp.db.postgresql.performance |
|---|---|
| Message-ID | <[email protected]> |
"Steinar H. Gunderson" <[email protected]> writes: > RDTSC is a bad source of information for this kind of thing, as the CPU > frequency might vary. One thought that was bothering me was that if the CPU goes idle while waiting for disk I/O, its clock might stop or slow down dramatically. If we believed such a counter for EXPLAIN, we'd severely understate the cost of disk I/O. I dunno if that is the case on any Windows hardware or not, but none of this thread is making me feel confident that we know what QueryPerformanceCounter does measure. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match