1、设置min_parallel_table_scan_size='500MB'; 则:Workers Planned: 2 2、设置min_parallel_table_scan_size=‘'200MB'; 则:Workers Planned: 3 3、设置min_parallel_table_scan_size=‘‘100MB'; 则:Workers Planned: 4 · 改变max_parallel_workers_per_gather进程分配规则 改变workers分配规则: 实际上,...
min_parallel_index_scan_size,索引扫描数据量的最小阈值,超过该值才会考虑使用并行 force_parallel_mode,强制使用并行模式 parallel_leader_participation,并行的 leader 是否参与并行,默认为 on 生成并行执行计划的相关函数: 以Parallel Seq Scan 为例,介绍生成并行表扫描计划所涉及的一些重要函数。 (1)compute_paralle...
(8 rows) 备注:执行多次,执行时间大概都在4秒多点,从执行计划中看到走了并行顺序扫描“Parallel Seq Scan on test_big1”,再细看“Workers Launched: 4”,表示开启了四个并行进程。 --查看并行顺序扫描进程 备注:图中可看到出现了四个 parallel worker 进程。 三PostgreSQL9.5 测试 测试之前先把 PostgreSQL 9.6...
-> Parallel Seq Scan on prt2_p1 t2 --prt2_p1 与prt1_p1 两个分区连接 Filter: ((b >= 0) AND (b <= 10000)) -> Parallel Hash -> Parallel Seq Scan on prt1_p1 t1 Filter: (b = 0) (17 rows)
Workers Planned:2Workers Launched:2->Parallel Seq Scanonperson (cost=0.00..256165.33rows=42778width=126) (actualtime=0.045..1213.880rows=33594loops=3)Filter: (age=20)RowsRemovedbyFilter:3299739PlanningTime:0.771ms ExecutionTime:1290.852ms (8rows) ...
-> Parallel Seq Scan on test_outer o (cost=0.00..177447.41 rows=12 width=8) Filter: ((o_w_id = 29) AND (o_c_id = 1831)) (9 rows) 1 2 3 4 5 6 7 8 9 10 11 12 13 从上面的执行计划看,针对表的过滤条件比较好,筛选后只有29条记录,因此针对这张表的条件建立了一个物化视图,用...
-> Parallel Seq Scan on people (cost=0.00..96382.26 rows=2917 width=0) (actual time=378.831..379.341 rows=3333 loops=3) Filter: (atpgconn2018 = 'Y'::bpchar) Rows Removed by Filter: 3330000 Planning Time: 0.063 ms Execution Time: 386.532 ms ...
-> Parallel Seq Scan on test (cost=0.00..99608.60 rows=3600060 width=15) (actual time=0.019..356.146 rows=288000 7 loops=3) Planning Time: 0.134 ms Execution Time: 1635.238 ms (18 rows) Time: 1636.838 ms (00:01.637) 1. 2.
由于PostgreSQL的其他部分使用进程,而不是线程,因此创建三个工作进程的查询可能比传统的执行速度快4倍。 -> Parallel Seq Scan on prt2_p2 t2_1 --prt2_p2 与…
Finalize Aggregate (cost=397.10..397.11 rows=1 width=32) -> Gather (cost=397.08..397.09 rows=2 width=32) Workers Planned: 3 -> Partial Aggregate (cost=397.08..397.09 rows=1 width=32) -> Parallel Seq Scan on tenk1 (cost=0.00..386.67 rows=4167 width...