Class that represents a query graph.
A parsed query is converted into a graph with each node in the graph corresponding to a filter.
| Property | Description | 
|---|---|
| empty | Returns true if the graph is empty. | 
| root | Root node of the graph. Can be null. | 
| Constructor | Description | 
|---|---|
| QueryGraph | Constructor. Creates a new query graph. | 
| Method | Description | 
|---|---|
| Optimize | Optimize the graph. |