Viewing the Execution Plan and Costs¶
The execution plan shows how the table referenced by the SQL statement will be scanned (sequential scan or index scan).
The SQL statement execution cost indicates the duration for executing a statement (measured in cost units that are arbitrary, but conventionally mean disk page fetches).
Follow the steps below to view the plan and cost for a required SQL query:
Enter the query or use an existing query in the SQL Terminal and click
on the SQL Terminal toolbar to view explain plan.To view explain plan with analyze, click the drop-down from
, select Include Analyze, and click .The Execution Plan opens in tree view format as a new tab at the bottom by default. The display mode has a tree shape and text style.
Note
The data shown in tree explain plan and visual explain may vary, since the execution parameters considered by both are not the same.
Following are the parameters selected for explain plan with/without analyze and the columns displayed:
Table 1 Explain plan options¶ Explain Plan Type
Parameter
Column
Include Analyze deselected (default setting)
Verbose, Costs
Node type, startup cost, total cost, rows, width, additional Info
Include Analyze selected
Analyze, Verbose, Costs, Buffers, Timing
Node type, startup cost, total cost, rows, width, Actual startup time, Actual total time, Actual Rows, Actual loops, Additional Info
The Additional Info column contains predicate information (filter predicate and hash condition), distribution key, output information, and node type.
In Tree Format, nodes are categorized into 16 types. Each node is indicated with an icon of the corresponding type. The following table lists the node types and icons.
Table 2 Node types and icons¶ Node Category
Icon
Aggregate
Group Aggregate
Function
Hash
Hash Join
Nested Loop
Nested Loop Join
Modify Table
Partition Iterator
Row Adapter
Seq Scan on
Set Operator
Sort
Stream
Union
Unknown
You can hover over highlighted cells to identify the heaviest, costliest, and slowest nodes. Cells can only be highlighted in Tree Format.
If multiple queries are selected, the explain plan with/without Include Analyze selected is displayed only for the last query.
Each execution plan generated from executing a query is opened on a new tab page.
If the connection is lost during execution but the database remains connected in Object Browser, the Connection Error dialog box is displayed with the following options:
OK: Connects to the database again to obtain the execution plan and cost.
Cancel: Disconnects the database from Object Browser.
Toolbar menu in the Execution Plan window:
Toolbar Name
Icon
Description
Tree Format
This icon is used view explain plan in tree format.
Text Format
This icon is used to display explain plan in text format.
Copy
This icon is used to copy selected data from the Result tab to clipboard. The shortcut key is Ctrl+C.
Commit
This icon is used to save the explain plan in text format.
For information about refresh, SQL preview, and search bar, see Execute SQL Queries.
After you click Refresh, the EXPLAIN ANALYZE query is executed again, and the execution plan is updated.
The result is displayed on the Messages tab.