Anne Rosset wrote:
> Thanks Steve.
> I found this:
> "
> Fix performance problems with autovacuum truncation in busy workloads (Jan 
> Wieck)
> Truncation of empty pages at the end of a table requires exclusive lock, but 
> autovacuum was coded to fail (and release the table lock) when there are 
> conflicting lock requests. Under load, it is easily possible that truncation 
> would never occur, resulting in table bloat. Fix by performing a partial 
> truncation, releasing the lock, then attempting to re-acquire the lock and 
> continue. This fix also greatly reduces the average time before autovacuum 
> releases the lock after a conflicting request arrives."
> So that is not the fix? 
> (Sorry to ask a second time but I really need to make sure).

That's the commit that created the bug, AFAIU.  It's a fix for a serious
problem, but we overlooked that it introduced some other problems which
is what you're now seeing.

Álvaro Herrera      
PostgreSQL Development, 24x7 Support, Training & Services

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