PostgreSQL 9.6 beta 2 发布了，与9.5版本相比，新版本在配置文件中引入了新的参数 ：
max_parallel_workers_per_gather: the number of workers that can assist a sequential scan of a table;
min_parallel_relation_size: the minimum size that a relation must have for the planner to consider the use of additional workers;
parallel_setup_cost: the planner parameter that estimates the cost of instantiate a worker;
parallel_tuple_cost: the planner parameter that estimates the cost of transferring a tuple from one worker to another;
force_parallel_mode: parameter useful for testing, strong parallelism and also a query in which the planner would operate in other ways.