[OE-core] [PATCH 3/3] prserv/db: Use DELETE instead of WAL journal mode

[Leonardo Sandoval]

On 09/17/2015 03:01 PM, Burton, Ross wrote:
> On 15 September 2015 at 15:59, <leonardo.sandoval.gonzalez at 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
>