Question

java.sql.SQLException: database is locked
    at org.sqlite.DB.throwex(DB.java:288)
    at org.sqlite.NestedDB.prepare(NestedDB.java:115)
    at org.sqlite.DB.prepare(DB.java:114)
    at org.sqlite.Stmt.executeQuery(Stmt.java:89)

When I make a query I get this exception. I read up on it on SA and Google, and the most common conclusion is that someone started making another query which never finished. The problem I’m having is that I’ve never made a query on this DB on this machine before. I downloaded the db file from where I hosted it (I created it earlier) and haven’t done anything with it, so I don’t know why it would be locked. When I do a query using a program called SQLite Database Browser, it works just fine. Thanks for the help, I’ll provide more info if need be, just let me know.

adapter = new DbAdapter();
ResultSet info;
ResultSet attributes;
for (int i = 1; i < 668; i++) {
    if (i%50 == 0) {
        System.out.print('.');
    }
    info = adapter.makeQuery("SELECT * FROM vehicles WHERE id = '" + i + "'");
    attributes = adapter.makeQuery("SELECT * FROM vehicle_moves WHERE vehicle_id = '" + i + "'");
    if(info.next()) {
        base = new (info, attributes);
    }

    vehicleArray[i] = base;
}
System.out.println("Done.");
info.close();
attributes.close();
adapter.close();

Above is the code where this is occurring. I did some homework throughout my code and sure enough the problem is in this code, other DB queries work just fine. Anything jump out at you guys?

Answer 1

SQLite itself can most certainly handle doing a query while the results of another query are being processed. It’d be terribly useless if that couldn’t be done! What’s more likely to cause problems is if you’ve got two connections to the database open at once. I don’t know that DbAdapter class at all – not what package it is in, or what module provides it – but if it is assuming that it can open many connections (or if it isn’t maintaining proper connection hygiene) then that most certainly would be a cause of the sort of problems you’re seeing. Look there first.