一．安装过程如下：进入postgreSQL安装包的contrib/pg_stat_statements目录，执行编译和安装动作：用root用户
make && make install
二．安装成功后，在data/postgresql.conf中，进行配置：
shared_preload_libraries = 'pg_stat_statements'
pg_stat_statements.max = 1000
pg_stat_statements.track = all
三．重新启动 postgresql，创建sql语句：
create extension pg_stat_statements;
四.查询哪些sql语句执行效率慢：
select query ,calls,total_time,(total_time/calls) as average,rows,100.0 * shared_blks_hit /nullif(shared_blks_hit + shared_blks_read,0) as hit_precent
from pg_stat_statements
order by average desc limit 10;
五．统计结果一直都在，重启也不会清零，那么统计结果如何清零重新统计呢？执行下面SQL即可：
select pg_stat_statements_reset() ;