Hi,
On 2016-11-22 15:49:27 -0500, Robert Haas wrote:
> I think you are almost right. When the server is running, there are
> files in pg_stat_tmp but not pg_stat; when it is shut down, there are
> files in pg_stat but not pg_stat_tmp. Of course the data can never be
> ONLY in the collector's backend-local memory because then nobody else
> could read it.
> I don't actually really understand the reason for this distinction.
pg_stat_tmp commonly is placed on tmpfs/a ramdisk.
But I'm a bit confused too - does this make any sort of difference?
Because the startup path for crash recovery is like this:
void
StartupXLOG(void)
{
...
/* REDO */
if (InRecovery)
{
...
/*
* Reset pgstat data, because it may be invalid after recovery.
*/
pgstat_reset_all();
so it seems quite inconsequential whether we write out pgstat, because
we're going to nuke it either way after an immediate shutdown?
Greetings,
Andres Freund
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