SQL/MP Query Guide

Analyzing Query Performance
HP NonStop SQL/MP Query Guide—524488-003
6-52
Nested Inner Join
Example 6-33. EXPLAIN Plan for Nested Inner Join (page 1 of 2)
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Query plan 1 : Will utilize parallel execution
SQL request : Select
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Plan step 1
Each operation is performed in parallel for this step
Each ESP will read one of the following partitions:
\SQL1.$DATA3 \SQL1.$DATA4 \SQL1.$DATA2
The ESP's will be started in the cpu's numbered
0 2 3
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Operation 1.0 : Scan
Table : \SQL1.$DATA2.WISCREG.TENKTUP1
with correlation name A
Access type : Record locks, stable access
Lock mode : Chosen by the system
Column processing : Requires retrieval of 16 out of 16 columns
Access path 1 : Primary, partitioned
SBB for reads : Virtual
Begin key pred. : None
End key pred. : A.UNIQUE2 < 10
Index selectivity : Expect to examine 0.0133% of rows from table
Index pred. : None
Base table pred. : None
Executor pred. : None
Table selectivity : Expect to select 0.0133% of rows from table
Expected row count: 10 rows after the scan
Operation cost : 152
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Plan step 2 : Perform an Inner Join
Join strategy : Nested Join
Each operation is performed in parallel for this step
Each ESP from previous step will join one of the following partitions:
\SQL1.$DATA2
Each ESP will perform a Nested Join (parallel access)
Characteristic : Joins a row resulting from plan step 1