SQlite3: issue a PRAGMA optimise before closing each database connection

[solracsf]

What would you like to be added:

To achieve the best long-term query performance without the need to do a detailed engineering analysis of the application schema and SQL, it is recommended that applications run "PRAGMA optimize" (with no arguments) just before closing each database connection.

This pragma is usually a no-op or nearly so and is very fast.

Why is this needed:

https://www.sqlite.org/pragma.html#pragma_optimize

[davies]

It's better to do this outside of juicefs, for example, before mount or after umount.

[solracsf]

How can this be done on mount/umount and not application (juicefs) side as it is recommended to be performed

"just before closing each database connection"

?

[davies]

It's used to optimize the database in disk, can be issued by sqlite cli.