A "rescue" version of Box.removeAll() for DBs that reached their size limit.

removeAllMultiTx.java

    /**
     * A "rescue" version of Box.removeAll() for DBs that reached their size limit.
     * Removes data in multiple transactions of increasing size to minimize required additional disk space.
     * <p>
     * Note that this method is not transactional, so it might fail in between, with any number of objects removed.
     * Thus, you should persistently track the state yourself, e.g. by setting a SharedPreferences flag to indicate
     * that removal is in progress. If this methods fails, you can check this flag to retry at a later point.
     * Only once this method succeeds, this flag should be cleared.
     * <p>
     * It's recommended to increase the max. DB size to ensure addition capacity is available for this method.
     */
    private void removeAllMultiTx(Box box) {
        int removeCount = 1;
        Query query = box.query().build();

        int opsForRemoveCount = 0;
        Log.i("ObjectBox", "Starting clean...");
        Log.i("ObjectBox", "Initial count: " + box.count());
        long removedSum = 0;
        while (true) {
            List toRemove = query.find(0, removeCount);
            if (toRemove.isEmpty()) {
                Log.i("ObjectBox", "Done, count: " + box.count());
                break;
            }
            // Log.i("ObjectBox", "Before remove:\n" + CallAppApplication.boxStore.diagnose());
            Collections.reverse(toRemove);
            box.remove(toRemove);
            removedSum += toRemove.size();
            // Log.i("ObjectBox", "After remove:\n" + CallAppApplication.boxStore.diagnose());

            opsForRemoveCount++;
            if (opsForRemoveCount == 4) {
                // Delete 4 * removeCount entities, before doubling removeCount:
                // 1) minimize required additional space (starting with removeCount = 1)
                // 2) increase likeliness that enough free pages are available as removeCount grows
                removeCount = Math.min(10000, removeCount * 2);
                opsForRemoveCount = 0;
                Log.i("ObjectBox", "Removed: " + removedSum);
            }
        }
    }