folks,
Does postgres make an effort to create a file with physically continuous
blocks?
Thanks!
hi, folks!
I see that shared cache is implemented by system v shared memory. I wonder
whether data in this area can be swapped out to disk.
Isn't it bad that we read data from disk, put data in shared cache, and
finally data in shared cache is swapped to disk again!
Why not use shmctl(..SHM_LOCK.
Hi, folks,
I trace the running postgres, and I found that there are some randoms writes
in xlog files!
To my impression, log file writing is always sequential, how come random
writes happen?
Thanks in advance!
Hi, folks,
in src/template/darwin:
# Select appropriate semaphore support. Darwin 6.0 (Mac OS X 10.2) and up
# support System V semaphores; before that we have to use POSIX semaphores,
# which are less good for our purposes because they eat a file descriptor
# per backend per max_connection slot.
I found that postgres uses different semaphore system call on some different
operating systems.
For example, I found that on linux, System V semaphore (semop etc.) is used
to implement locking, while on Darwin, POSIX semaphore (sem_wait, sem_post
etc.) is used.
linux and Darwin support both System
Hi, folks,
I'm a newbie to postgres. I'm confused with xlog and clog.
To my initial understanding, xlog is the periodic checkpoint log for data,
while clog is for commit log (very unclear for me ...)
Thanks!
Thanks for your reply.
Yes, i mean disk may lie to os.
On Fri, Dec 3, 2010 at 12:14 PM, Stefan Kaltenbrunner
wrote:
> On 12/03/2010 06:43 PM, Heikki Linnakangas wrote:
>
>> On 03.12.2010 13:49, flyusa2010 fly wrote:
>>
>>> When writing log, dbms should synchrono
When writing log, dbms should synchronously flush log to disk. I'm
wondering, if it is possible that the logs are in disk cache, while the
control is returned to dbms again, so dbms thinks logs are persistent on
disk. In this case, if the disk fails, then there's incorrectness for dbms
log writing,
