SQL/MP Query Guide

Analyzing Query Performance
HP NonStop SQL/MP Query Guide—524488-003
6-72
EXPLAIN Plan for Cursor UPDATE
EXPLAIN Plan for Cursor UPDATE
This EXPLAIN plan shows an UPDATE operation using a cursor.
The query updates the EMPLOYEE table (primary key EMPNUM) according to data in
the TABLES catalog table (primary key TABLENAME). The query follows:
EXPLAIN
UPDATE EMPLOYEE
SET JOBCODE = 105
WHERE EXISTS ( SELECT TABLENAME
FROM TABLES
WHERE TABLETYPE = 'VI' );
The total cost of the query is 54.
Example 6-43. EXPLAIN Plan for Cursor UPDATE (page 1 of 2)
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
Query plan 1 : Will utilize parallel execution
SQL request : Update
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
---------------------------------------------------------------------------
Plan step 1
Each operation is performed in parallel for this step
Each ESP will read one of the following partitions:
\SQL1.$DATA8
The ESP's will be started in the cpu's numbered
2
---------------------------------------------------------------------------
Operation 1.0 : Scan
Table : \SQL1.$DATA8.PERSNL.EMPLOYEE
with correlation name EMPLOYEE
Access type : Record locks, stable access
Lock mode : Chosen by the system
Column processing : Requires retrieval of 0 out of 6 columns
Access path 1 : Primary
SBB for reads : Virtual
Begin key pred. : None
End key pred. : None
Index selectivity : Expect to examine 100% of rows from table
Index pred. : None
Base table pred. : None
Type of Update : Cursor
SBB for Update : Requested by the optimizer