Storage backend migration script

[felixjogris]

Hi,

I started a storage backend migration script (https://github.com/felixjogris/PrivateBin/blob/migrate/migrate.php). It copies pastes, attachments, and comments from one backend (e.g. file system) to another one (e.g. a database). Both backends may be of same type, e.g. from database to database.
Before submitting a pull request, I'd like to discuss a few points:

• Is this command line script welcome?
• Better add a member function for listing all paste ids to AbstractData and derived classes, or better stick with reflection to gain access to private properties like migrate.php currently does?
• Better change all static properties (e.g. $_db or $_path) in data backend classes to non-static ones, or let migrate.php first read all pastes and comments to memory, and then write to the new storage backend?

Best,
Felix

[elrido]

Very nice work and a creative use of reflection! It parses flags and has a help message. It is certainly an enhancement that has been requested, see #359, so it would make sense to add it.

I would recommend to:

• reg. point 2: I'd recommend adding a new (public) member function - the _getExpiredPastes is already close to that, but has extra steps filtering the result and limits itself to a batch size, so it would be a simplified version of that
• reg. point 3: those static properties would be shared when we'd have two backends of the same type in play - since PrivateBin in normal operation will try and share the backend object via DI, making these properties non-static shouldn't impact memory usage, so I'd recommend changing it to non-static.
• assuming this script is used with larger instances that have hundreds or thousands of pastes and comments, it would probably be a bit slower, but more memory conserving, if the pastes and comments get converted one at a time (folding lines 53-58 into the loop starting at 44) instead of compiling an in-memory representation of all pastes and comments before storing them all
• it would be nice to have a unit test for this, at least a simple one that converts a paste with comment from file storage to sqlite in memory and back, validating the data is complete at each stage - I'm willing to write one
• create a new directory called bin and place it there
• update the INSTALL.md to mention that bin should also live outside the document root
• update the CREDITS.md and CHANGELOG.md, attributing your effort
• (on our side) also move the two other scripts into bin

[elrido]

Having merged your script in #1012, @felixjogris, I've now raised #1014 with the move of the other two scripts and the unit test. It does indeed work nicely and just as advertised! :-D Could you have a look at the PR, please?

I did discover that the third argument in getopt requires PHP >= 7.1, so I added a version check to the script. Also made it executable (it still works when called with php explicitly).