As I am reaching the end of successful summer, with Apache Derby and Google, I like to share with you a prototype that I've done using the tool, PlanExporter, which I've developed to Apache Derby.
You can visit this page to see the prototype.
This tool provides a high level view of the execution plans of complex queries you have executed. You can see the steps followed by the "Query Optimizer" of Derby, in order to execute the particular query. In this case Optimizer had followed a query plan with four "plan nodes", namely PROJECTION, HASH JOIN, TABLE SCAN and HASH SCAN. Intermediate results flow from the bottom of the tree to the top. In this case the filtered results of TABLE SCAN and HASH SCAN was given as the input for HASH JOIN. After performing the HASH JOIN the filtered result set given as a input to the PROJECTION node.
You can move the mouse point over an any node of the query plan to view set of available details about the execution at that step.
It is just the output that shown there. To convert to this output I had done lot of coding :).
Thanks for reading!