Intra-query Parallelism

Synonyms

Query parallelism

Definition

Intra-query parallelism is a form of parallelism in the evaluation of database queries, in which a single query is decomposed into smaller tasks that execute concurrently on multiple processors.

Key Points

Intra-query parallelism is achieved when several processors cooperate in the execution of a single query to improve the query’;s response time. Intra-query parallelism is orthogonal to inter-query parallelism, in which multiple independent requests execute concurrently on several processors to improve the overall system throughput.

There exist two forms of intra-query parallelism: operator-level parallelism and intra-operator parallelism. Operator-level parallelism is obtained by executing concurrently several operators of the same query. For example, consider a simple query that consists of a scan operator and an aggregation. The scan operator uses a selection condition to filter tuples. The aggregation calculates some statistics over all...