文件名称：SQL查询处理机制-Greenplum 数据库基础培训V1.2
文件大小：7.92MB
文件格式：PPT
更新时间：2024-05-15 15:14:47
Greenplum 中文
SQL查询处理机制 * Instructor Notes (animated slide) Greenplum creates a number of database processes (postgres processes) to handle the work of a query. (click) On the master, the query worker process is called the query dispatcher (QD). The QD is responsible for creating and dispatching the query plan, and for accumulating and presenting the final results. (click) On the segments, a query worker process is called a query executor (QE). A QE is responsible for completing its portion of work and communicating its intermediate results to the other worker processes. For each slice of the query plan there is at least one worker process assigned. A worker process works on its assigned portion of the query plan independently. During query execution, each segment will have a number of processes working on the query in parallel. (click) Related processes that are working on the same portion of the query plan are referred to as gangs. (click) As a portion of work is completed, tuples flow up the query plan from one gang of processes to the next. This inter-process communication between the segments is what is referred to as the interconnect component of Greenplum Database.