Query report error in Greenplum: not supported in DXL

Products

• VMware Tanzu Greenplum

Issue/Introduction

Symptoms:
Logging may report the following error, but the query still completes.

GPDB Expression type: {PARAM :paramkind 0 :paramid 1 :paramtype 16 :paramtypmod -1} not supported in DXL""

Environment

Cause

This error occurs because GP ORCA Optimzier doesn't support a few features yet.

Here are the current feature limitations:
https://docs.vmware.com/en/VMware-Greenplum/6/greenplum-database/admin_guide-query-topics-query-piv-opt-changed.html

Note: This liist is subject to change.

These are unsupported features when GPORCA is enabled (the default):
Indexed expressions (an index defined as expression based on one or more columns of the table)
PERCENTILE window function
External parameters
These types of partitioned tables:
Non-uniform partitioned tables.
Partitioned tables that have been altered to use an external table as a leaf child partition.
SortMergeJoin (SMJ)
Ordered aggregations
These analytics extensions:
CUBE
Multiple grouping sets
These scalar operators:
ROW
ROWCOMPARE
FIELDSELECT
Multiple DISTINCT qualified aggregate functions
Inverse distribution functions

Resolution

When GPDB encounters this use case, it will automatically switch to the legacy optimizer. The query can still complete and the message is information only.