查看PostgreSQL数据库中SQL语句的执行计划

[postgres@rhel73 ~]$ psql psql (9.6.0) Type "help" for help. postgres=# create table t(k serial primary key, v integer); CREATE TABLE postgres=# insert into t(v) select trunc(random()*10) from generate_series(1,100000); INSERT 0 100000 postgres=# explain analyze select count(*) from t; QUERY PLAN --------------------------------------------------------------------------------------------------------------- Aggregate (cost=1694.48..1694.49 rows=1 width=8) (actual time=17.810..17.811 rows=1 loops=1) -> Seq Scan on t (cost=0.00..1444.18 rows=100118 width=0) (actual time=0.025..10.825 rows=100000 loops=1) Planning time: 1.269 ms Execution time: 17.914 ms (4 rows) postgres=# explain analyze select * from t where k=1000; QUERY PLAN ---------------------------------------------------------------------------------------------------------- Index Scan using t_pkey on t (cost=0.29..8.31 rows=1 width=8) (actual time=0.011..0.011 rows=1 loops=1) Index Cond: (k = 1000)----->>>此处是走索引的标志,类似于Oracle 执行计划中的"access"部分. Planning time: 0.368 ms Execution time: 0.042 ms (4 rows) postgres=# 注意: (cost=0.29..8.31 rows=1 width=8) ------->>>这是PG优化器预估的数据 (actual time=0.011..0.011 rows=1 loops=1) ------->>>这是PG实际执行之后的数据.