[gears-users] making offline SQLite database from online source

[Wiolowan]

I'm tryping to populate offline SQLite database from online source
using AJAX library,
The main loop in the callback function is:

function dbLoad(ofs, limit) {
.....
    req.onreadystatechange = function() {
        if (req.readyState == 4) {
                    res=req.responseJS.entry;
                        offset+=1000
                        dbLoad(offset,1000)
                        db.execute('begin');
                        for(var i=0; i<res.length; i++){
                                db.execute('insert into dbtable values 
('+res[i]+')');
                        }
                        db.execute('commit');
...
}

The database has 240,000 rows, 22Mb.
If the loading is uninterrupted (240x recursive calling of dbLoad),
the import of the table is OK.

If I interrupt loading, the offline SQLite database file  is created,
and the following SQL query:

offset = db.execute('SELECT count(*) as count FROM dbtable').field(0)
--yields the number of rows (say, 3000).

However when I try to launch further importing, the above BEGIN-COMMIT
block is unstable - sometimes it works alright, and sometimes it gives
the error caught by Firebug:

Database operation failed. ERROR: SQL logic error or missing database
DETAILS: SQL logic error or missing database
db.execute('commit');
Database operation failed. ERROR: SQL logic error or missing database
DETAILS: SQL logic error or missing database
db.execute('begin');

The error may (and may not) arise both during stepwise debugging and
during uninterrupted running.
The database is not missing: when I add db.open('...') - db.close()
pair an error "Database is already open" pop up on first db.open().

What's the catch?

Thank you.