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How do you read an execution plan?
Execution Plan Order Each icon in the graphical execution plan is known as an operator, and the most common way to read a plan is by starting with the top right most operator and following the arrows to the left.
What is an execution plan in SQL?
An execution plan in SQL Server is a simple graphical representation of the operations that the query optimizer generates to calculate the most efficient way to return a set of results.
How do I view a query plan in Toad?
TOAD allows you to easily see the explain plan for the currently executed SQL statement. This is visualized on the Explain Plan tab in the results panel. Figure 3.41 illustrates a rather simple explain plan. Ctrl+E also runs and displays an explain plan.
How to read an execution plan for a two table join?
Here is the execution plan for a two-table join: Each line in the plan is a separate operation. These operations are linked via a parent/child relationship. The plan is a tree. The SELECT statement at the top is the root, the tables are the leaves at the bottom, and in between you’ll find a whole host of possible operations.
How to read an execution plan in Oracle?
Pass the rows from the tables at steps 7, 8, and 9 up to the UNION-ALL in step 6. This step combines the rows into one dataset. Work back up the tree to the HASH JOIN in step 3. Join the rows from steps 4 and 6, passing the surviving rows up to the HASH GROUP BY in step 2.
What does the PX coordinator row in Oracle mean?
The PX COORDINATOR row source represents the QC or Query Coordinator which controls and schedules the parallel plan appearing below it in the plan tree. Index row sources using bitmap indexes appear in the EXPLAIN PLAN output with the word BITMAP indicating the type of the index.
Which is the EXPLAIN PLAN statement in Oracle?
19.1 Understanding EXPLAIN PLAN The EXPLAIN PLAN statement displays execution plans chosen by the Oracle optimizer for SELECT, UPDATE, INSERT, and DELETE statements. A statement’s execution plan is the sequence of operations Oracle performs to run the statement. The row source tree is the core of the execution plan.