Bug 161086 [Viewers] performance problem in AbstractTreeViewer.internalExpandToLevel
If you expand to ALL_LEVELS, internalExpandToLevel will call createChildren even if the element has no children, i.e. it does not check if the element is expandable. Found this while experimenting with the Quick Access feature (enter "con", then delete all three characters one at a time).
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
if (comparator == null) {
			return size;
		}
		int min = lastInsertion, max = size - 1;
		while (min <= max) {
			int mid = (min + max) / 2;
			Object data = items[mid].getData();
			int compare = internalCompare(comparator, parentPath, data, element);
			if (compare == 0) {
				return mid;
			}
			if (compare < 0) {
				min = mid + 1;
			} else {
				max = mid - 1;
			}
		}
		return min;
	}
	/**
	 * Returns the index where the item should be inserted. It uses sorter to
	 * determine the correct position, if sorter is not assigned, returns the
	 * index of the element after the last.
	 * 
	 * @param parent
	 *            The parent widget
	 * @param sorter
	 *            The sorter to use.
	 * @param startIndex
	 *            the start index to start search for position from this allows