In Greenplum Database, the default GPORCA optmizer co-exists with the Postgres Planner.
These sections describe GPORCA functionality and usage:
Overview of GPORCA
GPORCA extends the planning and optimization capabilities of the Postgres Planner.
Enabling and Disabling GPORCA
By default, Greenplum Database uses GPORCA instead of the Postgres Planner. Server configuration parameters enable or disable GPORCA.
Collecting Root Partition Statistics
For a partitioned table, GPORCA uses statistics of the table root partition to generate query plans. These statistics are used for determining the join order, for splitting and joining aggregate nodes, and for costing the query steps. In contrast, the Postgres Planner uses the statistics of each leaf partition.
Changed Behavior with the GPORCA
There are changes to Greenplum Database behavior with the GPORCA optimizer enabled (the default) as compared to the Postgres Planner.
There are limitations in Greenplum Database when using the default GPORCA optimizer. GPORCA and the Postgres Planner currently coexist in Greenplum Database because GPORCA does not support all Greenplum Database features.