Plan Graph

The Plan graph dialog displays a graphic representation of all the operations that are run by the system during a query execution.

Each operation is shown as an ellipse with a particular color that identifies the type of operation. The plan graph is often called an HTML plan or a bubble plan. The graph shows the following types of operations:

• Green indicates that the operation is a join or nested loop operation.
• Silver is a scan operation.
• Yellow is a SPU operation, for example, GROUP or APPEND.
• Blue is a SPU/Host operation, for example, SORT or LIMIT.
• White represents all other operations such as a materialize and others.

To view a plan graph of a SQL query, you can right-click a query in the System folder Active Queries or Finished Queries view, you can right-click a query in the Query History results, or in the SQL Queries folder views. When you create a SQL query to run on the system, you can also select More options > Plan graph to display the graph. A sample plan graph is shown in the following figure.

Figure 1. Sample plan graph

The dialog shows the EXPLAIN SQL query at the top, and offers a zoom control which you can use to increase or decrease the size of the graphics in the window. The color of the border of the ellipses also indicates normal or warning conditions. A black border is the default and represents a normal condition. If an ellipse has a red border, the operation inside the ellipse could impact the query execution time because it might be a bottleneck that could negatively affect the query performance. This can help users to identify areas where query changes could improve query performance. When you review a plan graph, keep in mind that the execution order is from right to left, from bottom to top. The following figure shows a typical plan with two branches, a right and a left.

Figure 2. Plan graph reading order

For the plan in the figure, the actions the right branch (if one exists) are executed first, in order from the bottom right node to the top of the branch. Then, the system executes the nodes in the left branch from bottom right to left back to the top of the branch, then the system executes the nodes back through to the top of the plan tree. In this sample plan diagram, the nodes are executed in the following order: I, H, E, K, J, G, F, D, C, B, A.