Thread: Side effect of synchronous_commit = off
I was wondering whether setting synchronous_commit = off will have the following side effect. (1) Process A issues UPDATE command on row x, from false to true. (2) After that, Process B READ from row x. Is it possible that when Process B start to read row x, the "true" value is not being "flushed" to the table. Hence, processB will read the row x as false? If this situation will happen, is it possible that Process B may issues a command, use to "flush all" pending data to bewritten to disk? Thanks and Regards Yan Cheng CHEOK
Le 25/03/2010 08:49, Yan Cheng CHEOK a écrit : > I was wondering whether setting synchronous_commit = off will have the following side effect. > > (1) Process A issues UPDATE command on row x, from false to true. > (2) After that, Process B READ from row x. > > Is it possible that when Process B start to read row x, the "true" value is not being "flushed" to the table. Hence, processB will read the row x as false? > No, it's not possible. -- Guillaume. http://www.postgresqlfr.org http://dalibo.com
Being asynchronous, means that write-to-disk will be queued in kernel for later execution, ie, postgresql won't wait for its write confirmation, but they will occurr in a serial manner.
On Thu, Mar 25, 2010 at 4:49 AM, Yan Cheng CHEOK <yccheok@yahoo.com> wrote:
I was wondering whether setting synchronous_commit = off will have the following side effect.
(1) Process A issues UPDATE command on row x, from false to true.
(2) After that, Process B READ from row x.
Is it possible that when Process B start to read row x, the "true" value is not being "flushed" to the table. Hence, process B will read the row x as false?
If this situation will happen, is it possible that Process B may issues a command, use to "flush all" pending data to be written to disk?
Thanks and Regards
Yan Cheng CHEOK
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