sqlite: expose backup api

[geeksilva97]

Closes #55413

This PR exposes the SQLite Online Backup API, which allows database backup.

The API is inspired by better-sqlite3 https://github.com/WiseLibs/better-sqlite3/blob/master/docs/api.md#backupdestination-options---promise.

Multithreading caveats

As long as writes come from the same process and handle (sqlite*), the backup will continue progressing as expected. Other than that, it can cause the backup process to restart. From docs:

...If the source database is not an in-memory database, and the write is performed from within the same process as the backup operation and uses the same database handle (pDb), then the destination database (the one opened using connection pFile) is automatically updated along with the source.

Writes to an in-memory source database, or writes to a file-based source database by an external process or thread using a database connection other than pDb are significantly more expensive than writes made to a file-based source database using pDb (as the entire backup operation must be restarted...)

[geeksilva97]

This comment mentions that DatabaseSync needs to have only sync operations (makes sense).

The backup can be performed synchronously but I don't think it should be like that.

I wonder if indeed this PR would be more suitable for async API.

Any thoughts?

Thanks in advance

[codecov]

Codecov Report

Attention: Patch coverage is 81.42857% with 39 lines in your changes missing coverage. Please review.

Project coverage is 89.20%. Comparing base (808e6b3) to head (7b15cae).
Report is 88 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_sqlite.cc	81.42%	16 Missing and 23 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #56253      +/-   ##
==========================================
+ Coverage   89.18%   89.20%   +0.02%     
==========================================
  Files         662      662              
  Lines      191759   192178     +419     
  Branches    36911    36992      +81     
==========================================
+ Hits       171017   171439     +422     
+ Misses      13613    13562      -51     
- Partials     7129     7177      +48     

Files with missing lines	Coverage Δ
src/node_sqlite.h	70.00% <ø> (ø)
src/node_sqlite.cc	79.92% <81.42%> (+0.27%)	⬆️

... and 79 files with indirect coverage changes

[geeksilva97]

Failing test seems unrelated

[geeksilva97]

@jasnell @cjihrig do you think I need to check any memory leak using valgrind here? If so, is there a command in node that would allow me to do so? I saw some make test-valgrind but I don't know how it should be used.

Thanks in advance

[cjihrig]

do you think I need to check any memory leak using valgrind here?

That is not a requirement.

[jasnell]

If this is assumed to be a filesystem path, then handling it the same as our other fs APIs would be ideal. Paths can be expressed as either strings, Buffer, or file:// scheme URLs. If you're not familiar, there are internal utilities for normalizing these into a usable path.

[geeksilva97]

Makes sense. I will search for examples to see how to do that.

[geeksilva97]

Maybe that? https://github.com/nodejs/node/blob/main/lib/internal/fs/utils.js#L700-L720

[geeksilva97]

This makes sense but I'd like to see this in another PR. DB locations are all defined as strings in other parts of sqlite module - e.g. location in DatabaseSync.

We can have a PR dedicated to allowBuffer and URLs all at once.

Do you think it makes sense?