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Greenplum - Architecture and SQL by Leona Coffing, Tom Coffing

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Chapter 25 – Greenplum Explain

"Lucy, you got some 'splainin' to do!"

- Ricky Ricardo

How to See an EXPLAIN Plan

SELECT * FROM Employee_Table ;

image

Gather Motion 2:1 (slice1; segments: 2) (cost=0.00..2.09 rows=9 width=43)-> Seq Scan on emp_table (cost=0.00..2.09 rows=5 width=43)

To get an EXPLAIN you can either type the word EXPLAIN in front of any Greenplum SQL or click on the magnifying glass of Nexus.

The Eight Rules to Reading an EXPLAIN Plan

Gather Motion 2:1 (slice1; segments: 2) (cost=0.00..2.09 rows=9 width=43)-> Seq Scan on emp_table (cost=0.00..2.09 rows=5 width=43)

1.Always read an EXPLAIN plan from the bottom to the top.

2.A query ...

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