Working with Query Plans

Accessing Query Plans

There are three ways to see the query plans in the Web UI:

1. In the SQL Editor of the Web UI, the query plan can be accessed by clicking on the Show Query Plan icon:
   

   

   
   The query plan will be displayed for the query that currently contains the cursor.
2. It is also possible to investigate the query plan for the selected SQL if its text is marked before clicking “Show Query Plan”.
3. Query plans are also visible in the “Show Query Plan” Tab of DV Studio by selecting a query and clicking “Show Query Plan”. Please note that the query plans are archived along with the queries, so even if you change a view, it will not affect the plans of former queries.

Reading Query Plans

A query plan is read from bottom to top. In most cases, the source access will happen first, along the path processing on the CData Virtuality side and enriching data, with a final query node on top of the plan, indicating the result is returned to the user.

Example:

One issue can be seen here: in the join nodes, type conversion is happening for the IDs. CData Virtuality automatically casts to the bigger data type to be able to perform a join on different data types. Depending on the situation, it might make sense to perform this cast manually in the query to make it more efficient.