sqlite in-memory db and multithreading

Question

My application creates a in-memory database (:memory:) using sqlite as a back end.

I want my master thread to create a connection to a in-memory database and this connection to be shared by multiple threads. Is this possible? SQLite 3.7.8 is available for download right now.

Is the shared cached a possible way to go?

I don't think so since every connection to :memory: creates an independent DB in memory... see sqlite.org/inmemorydb.html — Yahia
– Yahia, Commented Oct 30, 2011 at 14:45
Maybe a duplicate of [this question][1] [1]: stackoverflow.com/questions/3267077/… — Nicolas Modrzyk
– Nicolas Modrzyk, Commented Oct 30, 2011 at 14:49
@NicolasModrzyk there is no answer to your link. However it is the same question, indeed. — cateof
– cateof, Commented Oct 30, 2011 at 14:53
@Yahia, yes, multiple open calls will make multiple in-memory databases; so, just do one open and share the connection among the threads. — Doug Currie
– Doug Currie, Commented Oct 30, 2011 at 16:06

Nisse Engström · Accepted Answer · 2014-11-20 13:41:10Z

3

If you open the connection to your in-memory database using serialized mode, then the connection may be shared among multiple threads.

For this to work, your SQLite must be compiled threadsafe -- this is the default.

Depending on your application, you may get better performance with a large shared cache to an on-disk database, or with WAL mode if you have many reader threads.

Example:

sqlite3 *pDb

if (sqlite3_open_v2(":memory:", &pDb, SQLITE_OPEN_FULLMUTEX, NULL) == SQLITE_OK) {

    start_thread1_with_db_handle(pDb);

    start_thread2_with_db_handle(pDb);

    // etc.
}

edited Nov 20, 2014 at 13:41

Nisse Engström

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answered Oct 30, 2011 at 16:00

Doug Currie

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1 Comment

Doug Currie Over a year ago

Not sure what you need; an example added to answer.

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