Thanks for the feedback. > Fragmentation would depend on cache behaviour. Would be worth testing > representative load.
I don't know what a representative load could be. Some users may want to delete tiles by zoom level, others by tiles range or others delete/update single tiles. > Strictly speaking MBTiles is only web-mercator:> > https://github.com/mapbox/mbtiles-spec/blob/master/1.2/spec.md#content-1> ; > That may not be a big issue, but we should be cautious about how we refer to > it. You are correct. > Shared store is almost certainly a bad idea. Yes SQLitle based specifications should not be used with shared stores. Le jeudi 19 mai 2016 à 20:36 +1000, Brad Hards a écrit : > > SQLite files cannot be managed as simple files. When connections to an > > SQLite > > database are open we should not delete, move or switch the associated file. > > Databases files can be filled with "empty space" after deleting an huge > > amount > > of data or can become fragmented after frequent inserts, updates or delete > > operations. > Fragmentation would depend on cache behaviour. Would be worth testing > representative load. > > > To remove the fragmented space (or the empty space), the VACUUM command > > needs to be executed. Although, performing a VACUUM command as a few > > drawbacks: > > > > - During a VACUUM twice the size of the original database file is > > required in > > disk. > > - During the VACUUM operation no access to the database is allowed. > > - The VACUUM operation copies the whole database which can take minutes. > There is also auto_vacuum, which works quite differently but may be useful: > https://www.sqlite.org/pragma.html#pragma_auto_vacuum > > Without that, or VACUUM, the cache will probably continue to grow. > > > MBTiles force us to have at least a file per layer and format. If we want to > > support more CRSs we will also need a file for each CRSs. By configuration > > it > > will be possible to configure the granularity of the database files. By > > default > > we will have a granularity per layer, crs, format and zoom level. > Strictly speaking MBTiles is only web-mercator: > https://github.com/mapbox/mbtiles-spec/blob/master/1.2/spec.md#content-1 > > That may not be a big issue, but we should be cautious about how we refer to > it. > > > SQLite allow multiple readers but only allow one writer at the time which > > will > > block the entire database. At most only one connection should be open to > > each > > SQLite database, the total number of open connections is limited by the > > number of open files allowed by the OS (in linux this is controlled by the > > ulimit). A connection pool that will control the number of open connections > > and that will be responsible to manage the connections will be implemented. > Shared store is almost certainly a bad idea. > > Brad > -- == GeoServer Professional Services from the experts! 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