Hi,

I have encountered a strange behavior when using in-memory databases with shared cache. If I open the database like this from multiple threads, everything works:

sqlite3_open_v2("file:foobar", &db, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_URI | SQLITE_OPEN_MEMORY | SQLITE_OPEN_SHAREDCACHE, NULL);

If I remove either the SQLITE_OPEN_URI flag OR the file: prefix, the shared cache does not work anymore. The reason for this seems to be that:

1. The flag is removed in sqlite3ParseUri for both cases (see https://github.com/sqlite/sqlite/blob/d63c76fb31a0e262fb12a93b171e95a4e30c1a2e/src/main.c#L3020).
2. The shared cache is only enabled if SQLITE_OPEN_URI is set in sqlite3BtreeOpen (see https://github.com/sqlite/sqlite/blob/d63c76fb31a0e262fb12a93b171e95a4e30c1a2e/src/btree.c#L2393).

Best regards, Michael Kuhn