Due to the database connection inherent to the SQLContainer, some of the methods from the container interfaces of Vaadin can not (or would not make sense to) be implemented. These methods are listed below, and they will throw an UnsupportedOperationException on invocation.
public boolean addContainerProperty(Object propertyId, Class<?> type, Object defaultValue) public boolean removeContainerProperty(Object propertyId) public Item addItem(Object itemId) public Object addItemAt(int index) public Item addItemAt(int index, Object newItemId) public Object addItemAfter(Object previousItemId) public Item addItemAfter(Object previousItemId, Object newItemId)
Additionally, the following methods of the Item interface are not supported in the RowItem class:
public boolean addItemProperty(Object id, Property property) public boolean removeItemProperty(Object id)
To properly implement the Vaadin Container interface, a getItemIds() method has been implented in the SQLContainer. By definition, this method returns a collection of all the item IDs present in the container. What this means in the SQLContainer case is that the container has to query the database for the primary key columns of all the rows present in the connected database table.
It is obvious that this could potentially lead to fetching tens or even hundreds of thousands of rows in an effort to satisfy the method caller. This will effectively kill the lazy loading properties of SQLContainer and therefore the following warning is expressed here:
It is highly recommended not to call the getitemIds() method, unless it is known that in the use case in question the item ID set will always be of reasonable size.