ubuntu=>explain(analysetrue, verbosetrue, bufferstrue)select*fromexplain_table; QUERY PLAN---Seq Scanonpg_temp.explain_table (cost=0.00..18.10rows=810width=72) (actualtime=0.012..0.014rows=2loops=1) Output: id, name, salary Buffers:localhit=1PlanningTime:0.070ms ExecutionTime:0.031ms (5rows...
AI代码解释 db_test=#explain(analyze,verbose,buffers)select*from db_test.t_ms_aj;QUERYPLAN---Seq Scan on db_test.t_ms_aj(cost=0.00..22.32rows=1032width=56)(actual time=0.060..1.167rows=1032loops=1)Output:c_bh,n_dm,c_ahBuffers:shared hit=12Planning Time:0.283ms Execution Time:1.730ms...
QUERY PLAN---Seq Scanontest (cost=0.00..676994.40rows=39571047width=6) (actualtime=0.011..7852.896rows=39500000loops=1)Filter: (a>500000)RowsRemovedbyFilter:500000PlanningTime:0.115ms ExecutionTime:9318.773ms (5rows) 总结 PostgreSQL 规划器的内部机制较为复杂,但通过本文解析,您应已掌握其核心运行逻辑...
https://www.sqlservercentral.com/articles/getting-a-query-execution-plan-in-postgresql
Execution Time: 5110.030 ms (8 rows) 如果规划器选择顺序扫描主路径且没有任何子路径,查询计划将如下所示: postgres=# explain analyze select * from test where a > 500000; QUERY PLAN --- Seq Scan on test (cost=0.00..676994.40 rows=39571047 width=6) (actual time=0.011.....
在执行任何 SQL 语句之前,PostgreSQL 优化器都会为它创建一个执行计划(Query Plan)。执行计划描述了 SQL 语句的具体实现步骤,例如使用全表扫描还是索引查找的方式获取表中的数据,连接查询使用 Nested Loop Join、Hash Join 还是 Sort Merge Join 算法,以及连接的顺序等等。
Execution Time: 5110.030 ms (8 rows) 如果规划器选择顺序扫描主路径且没有任何子路径,查询计划将如下所示: postgres=# explain analyze select * from test where a > 500000; QUERY PLAN --- Seq Scan on test (cost=0.00..676994.40 rows=39571047 width=6) (actual time=0.011.....
Execution Time: 0.102 ms 总的执行时间 (8 rows)EXPLAIN 输出举例说明 3 - union postgres=# explain (analyze, verbose, costs, buffers, timing) select 2 union select 2; -- union去重复 QUERY PLAN ---Unique (cost=0.06..0.07 rows=2 width=4) (actual time=0.010..0.013 rows=1 loops=1) ...
Execution Time,#执行执行计划的时间 常见扫描方式[5] PostgreSQL中数据扫描方式很多,常见有如下几种 Seq Scan 全表顺序扫描 db_test=# explain (analyze,verbose,buffers) select * from db_test.t_ms_aj; QUERY PLAN --- Seq Scan on db_test.t_ms_aj (cost=0.00..22.32 rows=1032 width=56) (actual...
Execution time: 0.160 ms 表明了实际的SQL 执行时间,其中不包括查询计划的生成时间 Index Scan:索引扫描加回表,相当于sqlserver index seek + key lookup postgres=> explain(ANALYZE,VERBOSE,BUFFERS) select * from class where st_no=2; QUERY PLAN