-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 02/28/2011 11:59 AM, Robert Hairgrove wrote: > I'm only beginning to delve into the possibilities offered by the VFS > API in SQLite. However, from what I have seen so far, it seems like a > very complete abstraction to me.
For one thing a SQLite database at runtime is actually multiple related files which makes things complicated. Things like their names matter. The existing VFS implementation assumes you will be working with names while the Chromium folk want a child process to not have permissions to open files and instead have a supervisor process do so as appropriate. The VFS API never anticipated this split process model passing handles rather than file/pathnames. > Why is it not possible to create a custom VFS for the intended purpose > and register it for the connections that need it? Because that custom VFS would be an almost duplicate of the existing VFS but with a few key places changed. If the changes were at the granularity of the VFS methods then it would be no problem to "inherit" as needed. Unfortunately they are within - for example wanting to use the xOpen method but changing only the open() call within. unixOpen() is 235 lines of code plus several helper functions. Having to copy all that code just to change one call on one line is not sustainable in the long term. It would be possible to remote the VFS instead - ie have a an implementation in the child process that just forwards all calls to the supervisor parent. If parent and child are using the same version of SQLite then this should work well at the expense of adding latency. It would however require the parent to implement security and resource limiting. The operating system does that for "free" for child processes appropriately initialized. Roger -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk1sB70ACgkQmOOfHg372QTFkwCgioqwaibI+6WrMedG4L0KOPKJ E5UAoLXUimQ3sLncdOiJL2Gbb+Nouvzb =NonM -----END PGP SIGNATURE----- _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
