sqflite database getting locked flutter - Warning database has been locked - flutter

Question

I am using SQLite in my flutter project and trying to figure out DB locked issue, in my scenario user is trying to download new data one time in day, and if that record exist it will update or it will insert a new record. My problem is even though I am using transaction and batch I am getting DB locked error, the only issue I can think of is getSongList() call as it calls DB out of that transaction or batch multiple times but that's read call and my code seems to fail during batch commit.
buildDB1(List<MusicData> _list, int version) async {
await openDb();
try {
_database.transaction((txn) async {
Batch batch = txn.batch();
for (var i = 0; i < _list.length; i++) {
// buildBatch(_list[i]);
MusicData musicData = _list[i];
int id = musicData.id;
if (musicData.pdfpage == 0 || musicData.pdfpage == null) {
PDFPAGE = "0";
} else {
PDFPAGE = (musicData.pdfpage).toString();
}
if (musicData.linkid == 0 || musicData.linkid == null) {
LINKID = "0";
} else {
LINKID = (musicData.linkid).toString();
}
// PDFPAGE = musicData.pdfpage as String;
// LINKID = musicData.linkid as String;
TITLE = musicData.title;
ALBUM = musicData.album;
SONGURL = musicData.songURL;
HINDINAME = musicData.hindiName;
MNAME = musicData.mname;
MSIGN = musicData.msign;
OTHER1 = musicData.other1;
OTHER2 = musicData.other2;
ENAME = musicData.ename;
ESIGN = musicData.esign;
LANGUAGE = musicData.language;
SONGTEXT = musicData.songtext;
Future<List<MusicData>> list1 =
getSongList("select * from songs where id=$id");
List<MusicData> list = await list1;
if (list.length != 0) {
String updateSQL =
"UPDATE SONGS SET pdfpage = $PDFPAGE, linkid = $LINKID, title = '$TITLE', album = '$ALBUM', songURL = '$SONGURL', hindiName = '$HINDINAME', mname = '$MNAME', msign = '$MSIGN', other1 = '$OTHER1', other2 = '$OTHER2', ename = '$ENAME', esign = '$ESIGN', language = '$LANGUAGE',songtext = '$SONGTEXT' WHERE id = $ID";
batch.rawUpdate(updateSQL);
// _database.rawUpdate(
// "UPDATE SONGS SET pdfpage = ?, linkid = ?, title = ?, album = ?, songURL = ?, hindiName = ?, mname = ?, msign = ?, other1 = ?, other2 = ?, ename = ?, esign = ?, language = ?,songtext = ? WHERE id = ?",
// [
// musicData.id,
// musicData.pdfpage,
// musicData.linkid,
// musicData.title,
// musicData.album,
// musicData.songURL,
// musicData.hindiName,
// musicData.mname,
// musicData.msign,
// musicData.other1,
// musicData.other2,
// musicData.ename,
// musicData.esign,
// musicData.language,
// musicData.songtext
// ]);
print("Record updated in db $id");
// _database.close();
} else {
String insertSQL =
"INSERT INTO SONGS (pdfpage, linkid, title,album,songURL,hindiName,mname,msign,other1,other2,ename,esign,language,songtext,isfav) VALUES ($PDFPAGE,$LINKID,'$TITLE','$ALBUM','$SONGURL','$HINDINAME','$MNAME','$MSIGN', '$OTHER1','$OTHER2','$ENAME','$ESIGN','$LANGUAGE','$SONGTEXT',0)";
batch.rawInsert(insertSQL);
// _database.insert('SONGS', musicData.toMap());
print("Record inserted in db $id");
}
}
Future<List> result = batch.commit();
});
SharedPreferences prefs = await SharedPreferences.getInstance();
await prefs.setInt('dbversion', version);
} catch (e) {
print(e);
}
}

Answer 1

getSongList should take a transaction argument. Basically use txn instead of _database in any db calls during a transaction. Otherwise it will hang and the warning is correct.
Also you might be hitting some race condition since you are not awaiting for batch.commit before the end of the transaction. You can try to replace:
Future<List> result = batch.commit();
by
await batch.commit();
Using pedantic could warn you about a missing await here.