Evaluate usage of up to date optimizations for SQLITE in line with current status of the project

[evilaliv3]

Proposal

I think that considering the current project status, the typical middle size deployment and the good stability over the years we could consider to revise the configuration of SQLITE.

In particular i propose we test the following changes, possibly scheduling for applying them into 5.1.0:

• journal_mode=WAL: while sqlite for compatibility reasons with old application still defaults to ROLLBACK mode, WAL is now widely used everywhere (e.g. in Android, IOS, Chrome, Whatsapp, etc.) with not known drawbacks
• synchronous=FULL: it is the default configuration; i opt for keeping it as is but making it explicit to unsure to verify the setting is as expeted; NORMAL mode would be faster and is definitely adopted very widely but i support FULL is best for us since it guarantees ACID behavior;
• cache_size=-32000: the default is 2MB since sqlite should work also on very small devices but probably globaleaks in mid size single tenant / multi tenant setups would definitely benefit of a larger cache of 32MB

[evilaliv3]

@rglauco @mspasiano: which are you evaluations? would you be in favor? do you have any recommendation?

Thank you!

[rglauco]

@evilaliv3 your chosen settings are the same i'd setup for me.