There are limitations in HAWQ when GPORCA is enabled. GPORCA and the legacy query optimizer currently coexist in HAWQ because GPORCA does not support all HAWQ features.
These HAWQ features are unsupported when GPORCA is enabled:
- Indexed expressions
- External parameters
- SortMergeJoin (SMJ)
- Ordered aggregations
- These analytics extensions:
- Multiple grouping sets
- These scalar operators:
DISTINCTqualified aggregate functions
- Inverse distribution functions
When GPORCA is enabled in HAWQ, the following features are known performance regressions:
- Short running queries - For GPORCA, short running queries might encounter additional overhead due to GPORCA enhancements for determining an optimal query execution plan.
ANALYZE- For GPORCA, the
ANALYZEcommand generates root partition statistics for partitioned tables. For the legacy optimizer, these statistics are not generated.
- DML operations - For GPORCA, DML enhancements including the support of updates on partition and distribution keys might require additional overhead.
Also, enhanced functionality of the features from previous versions could result in additional time required when GPORCA executes SQL statements with the features.