Transformation of directed acyclic graph query plans to linear query plans

摘要

Methods, computer-readable storage media and computer systems are provided for transforming a directed acyclic graph (“DAG”) query plan into a linear plan. A DAG query plan may include a first operator and a second operator that are scheduled to be executed in parallel. The DAG query plan may be modified so that the first and second operators are executed in series as an upstream operator and a downstream operator. A data unit output from the upstream operator may be marked to indicate that the data unit has been processed by the upstream operator. The data unit received as input at the downstream operator may be inspected to determine whether the data unit has been marked. Once in linear form, the query plan may be optimized to conserve computing resources.