Considerations when Using GPORCA

To execute queries optimally with GPORCA, consider certain criteria for the query.

Ensure the following criteria are met:

• The table does not contain multi-column partition keys.
• The table does not contain multi-level partitioning.
• The query does not run against master only tables such as the system table pg_attribute.
• Statistics have been collected on the root partition of a partitioned table.

If the partitioned table contains more than 20,000 partitions, consider a redesign of the table schema.

GPORCA generates minidumps to describe the optimization context for a given query. Use the minidump files to analyze HAWQ issues. The minidump file is located under the master data directory and uses the following naming format:

Minidump_date_time.mdp

For information about the minidump file, see the server configuration parameter optimizer_minidump.

When the EXPLAIN ANALYZE command uses GPORCA, the EXPLAIN plan shows only the number of partitions that are being eliminated. The scanned partitions are not shown. To show name of the scanned partitions in the segment logs set the server configuration parameter gp_log_dynamic_partition_pruning to on. This example SET command enables the parameter.

SET gp_log_dynamic_partition_pruning = on;