Group AMP Operations
Sometimes less parallelism is best. Tactical queries, for example, are more efficient when they engage fewer resources. On the other hand, short queries often require more than one AMP and cannot be accommodated with single‑AMP processing alone. The Optimizer looks for opportunities to transform what would otherwise be all-AMP query plan into a few-AMP plan. This few‑AMPs approach is called Group AMP.
The Group AMP approach not only reduces the number of AMPs active in supporting a query, it also reduces the locking level from a table‑level lock to one or more rowkey (specifically, partition and rowhash) locks in each AMP in the group. Removing the need for table-level locks eliminates two all-AMP steps from the query plan: