Display plan types

You can use EXPLAIN, HTML (also known as bubble), and text plans to analyze how a query is performed.

To obtain these plans, do the following tasks:

To obtain an EXPLAIN plan, add the EXPLAIN VERBOSE keyword before the SQL statement. The system displays the output to stdout unless you redirect it to a file.
```
 EXPLAIN VERBOSE SELECT * FROM foo;
```
To obtain an HTML plan, use either the EXPLAIN or SET command.
- The following is an example that uses EXPLAIN PLANGRAPH.
```
EXPLAIN PLANGRAPH SELECT * FROM foo;
```
  With EXPLAIN PLANGRAPH, the system displays the output to the nzsql terminal. You can copy and paste the output into a file that you can open in your browser.
- The following is an example that uses SET.
```
SET enable_print_plan_html=1;
SELECT * FROM FOO;
```
  The SET command saves the output to a file on the host. You can specify the location for the file. For example:
```
SET print_plan_path = ’/tmp’;
```
  In this case, the output would be saved to /tmp/plan#.html (The system begins with the number 1 and names subsequent output sequentially.)
- Whether you use EXPLAIN PLANGRAPH or SET, the output displays the query plan pictorially as a tree of nodes (ovals), representing how joins are processed. Use the following characteristics to interpret the representations.
  - Ovals with unbroken single lines and clear backgrounds (not shaded) are nodes that ran on the SPUs.
  - Shaded ovals represent nodes that the host (DBOS) executed.
  - Ovals with dashed lines represent virtual nodes (typically subquery scans).
  - Ovals with double lines represent fabric joins, which are streaming nodes that are either broadcast or distributed.
To obtain a text plan, use either the EXPLAIN or SET command. The system displays the output to the nzsql terminal unless you redirect it to a file.
```
EXPLAIN PLANTEXT SELECT * FROM foo;
OR
SET enable_print_plan_text=1;
SELECT * FROM foo;
```