Greenplum Stream Server (GPSS) merge operation reports "error: cannot parallelize an UPDATE statement that updates the distribution columns"

Products

• VMware Tanzu Greenplum

Issue/Introduction

Greenplum Stream Server (GPSS) versions 1.3.5 to 1.4.0 (inclusive) sets the planner to be the legacy planner (optimizer=off). This will not allow updates to columns that are part of the distribution key of the table.

Only the ORCA planner allows updated to columns that are part of the distribution key as it will cause the tuple to be moved/stored on another segment.

Environment

Product Version: 5.24

Resolution

Fix

This issue is fixed in Greenplum Stream Server (GPSS) 1.4.1.

In GPSS 1.4.1 and above, optimizer is set to on and allows updates to columns that are part of the distribution key.

Workaround

Alter the table to be distributed randomly.