Patch hashfile pragmas for ideal sqlite3 behaviour

[bbappserver]

• 10x sqlite cache.
• synchronous = 1 , just syncing normally much safer than not at all, perfectly fine as long you don't need to sync too often.
• WAL mode is just better in a number of ways.
• Not syncing WAL aggressively since we turned synchronous back on.

[t184256]

+1 for wal by default, I find it very useful

[lorddoskias]

Has any measurements been performed to see if those options indeed help? Because I run a basic test and at least in the hashing phase none of these options make a difference to performance.

[JackSlateur]

Hello,

WAL mode is enabled (https://github.com/markfasheh/duperemove/commit/1332ed48dc5522631047f06850c6bb37d6eea6b0) to path the way for further improvements

I have checked the other pragmas (most important is the "synchronous" one) and, while it does improve the safety of the database, the performance cost is high As our database is somehow volatile, I do not think this is a good tradeoff: in the worst case, it can be recreated from scratch

Thank you for your contribution!