Re: [PATCH 3/3] prserv/db: Use DELETE instead of WAL journal mode

[Leonardo Sandoval <leonardo.sandoval.gonzalez@linux.intel.com>]

On 09/18/2015 11:42 AM, Leonardo Sandoval wrote:
>
>
> On 09/17/2015 03:01 PM, Burton, Ross wrote:
>> On 15 September 2015 at 15:59,
>> <leonardo.sandoval.gonzalez@linux.intel.com>
>> wrote:
>>
>>> -        self.connection.execute("PRAGMA journal_mode = WAL;")
>>> +        self.connection.execute("PRAGMA journal_mode = DELETE;")
>>>
>>
>> Richard probably has a better memory than me but I seem to recall that
>> WAL
>> was a pretty serious speed improvement for the local host case.  Did you
>> benchmark the impact this change has?
>
> Unfortunately, I didn't do any benchmark.
>
> The problem with WAL is the following "All processes using a database
> must be on the same host computer; WAL does not work over a network
> filesystem." Using WAL, all PR values get lost after a PR server reboot,
> so we need a rollback journal. According to the documentation, the
> fastest of the these is "MEMORY" but it has its pros/cons:
>
> "The MEMORY journaling mode stores the rollback journal in volatile RAM.
> This saves disk I/O but at the expense of database safety and integrity.
> If the application using SQLite crashes in the middle of a transaction
> when the MEMORY journaling mode is set, then the database file will very
> likely go corrupt."
>

Ross: ignore my comment. The limitation "all process using a database 
must be on the same host" is not a limitation for us, because the 
PRserver is the only one talking to the database and this daemon/process 
is at the same place as the DB. So the root reason why WAL is not 
working is still unknown. Sending a V2 soon.

>>
>> Ross
>>