On 06 Apr 2017 at 11:28, Clemens Ladisch <clem...@ladisch.de> wrote:
> dave boland wrote: >> Being a little paranoid, I like to insure that the db file exists > > SQLite automatically creates an empty DB if you try to open > a nonexistent file, so you do not actually need to do anything. > >> and what state it is in (unconfigured, so needs to be made >> ready; or ready to accept data (or be read)). How do I do that? > > Store a DB version number somewhere. (You can do it like Android and use > PRAGMA user_version, or use an entry in some table.) If the version > number is not high enough, you have to create or update the database. > Do everything in a transaction to prevent a partially-created/updated > database: When my app starts, I check that the file in question actually *is* a database by doing some simple steps like open, selects from important tables, and a read/write to a globals table in the database that contains, for instance, the version number. I'm using PHP for this and it is a good use for try/catch at each step. If the step succeeds, I pass to the next. Since the database (one of many, in fact) belongs to the user, I can't hide it away somewhere. It also allows the user to add possibly older versions of the database file there, or completely other files such as READMEs. Files such as the latter will fail at an early step (usually with: file is not an SQLITE database) but I don't care why; they either pass or fail, and if they fail, the app then ignores them. Older versions of the db can be spotted by the version number in the globals table (as Clemens say above); they can then be silently upgraded to the current version. This will happen if I have, for instance, added a column or two to support some new feature. I don't user PRAGMA user_version because I keep reading that the continued existence of any particular PRAGMA is completely un-guaranteed. -- Cheers -- Tim _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
