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Reason for Different Explain Plans between Command Center and User Session

Environment 

 Product  Version
 Pivotal Greenplum  4.3.x
 OS  RHEL 6.x

Overview

Command center provides an option to check the query explain plan. Command Center executes the EXPLAIN <query> command in the background and provides the plan. If a user sets the parameter on the session for example, (GUC) optimizer=on within a session, but the actual execution plan might be completely different than what the command center is showing.

Cause

Command Center presents the plan based on the assumption that the users use the same database GUCs. Command Center is unable to access a user session information, so it is unable to acquire information about a session level parameters that may have been set by the user. 

Resolution

If most of the users use the same custom GUC (like optimizer = on) add it to the database configuration to get the right explain plan from Command Center.

 

 

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