Should I always use transactions in android sqlite?

Question

Here is a simple example:

public boolean containsId(Long userid) {
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.rawQuery("select * from " + getTableName() + " where id = " + userid, null);
    boolean rows = cursor.getCount() > 0;
    db.close();
    return rows;
}

I thought sqlite automatically starts a transaction. My colleague said I must always start a transaction.

So what is the right pattern? Should I start a transaction if I read data from database? I am sure that no other thread will write at this time in this table.

Answer 1

No changes can be made to the database except within a transaction. Any command that changes the database (basically, any SQL command other than SELECT) will automatically start a transaction if one is not already in effect. Automatically started transactions are committed when the last query finishes.

Transactions can be started manually using the BEGIN command. Such transactions usually persist until the next COMMIT or ROLLBACK command. But a transaction will also ROLLBACK if the database is closed or if an error occurs and the ROLLBACK conflict resolution algorithm is specified.

SQLite Query Language.

So yes, a transaction starts automatically. However, if you execute multiple queries without starting the transaction manually, multiple transactions are started and finished, which impacts performance negatively.
Furthermore, the automatic rollback mechanism only rolls back the single query when it fails.