The following bug has been logged online:

Bug reference: 2257
Logged by: Evgeny Gridasov
Email address: eugrid (AT) fpm (DOT) kubsu.ru
PostgreSQL version: 8.1.2 CVS
Operating system: Linux Debian
Description: Can' stop server while autovacuum is running
Details:

I needed to shutdown my server urgently, but I was unable to stop server by
pg_ctl -m fast.
Examining process list I found out that an autovacuum process is still
active.

autovacuum process (when active) did not respond to kill (TERM). Only kill
-9 helped to stop autovacuum process.

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TIP 2: Don't 'kill -9' the postmaster

"Evgeny Gridasov" <eugrid (AT) fpm (DOT) kubsu.ru> writes:
autovacuum does respond to shutdown requests, but in poking at this I
found that btree index vacuuming may fail to notice a pending interrupt
for long periods, if you've got large indexes. I've committed a fix
for that.

regards, tom lane

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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match

Tom Lane wrote:
Good catch. I have heard index creation doesn't cancel easily, but
never investigated.

--
Bruce Momjian http://candle.pha.pa.us
SRA OSS, Inc. http://www.sraoss.com

+ If your life is a hard drive, Christ can be your backup. +

---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match