pg_stat_activity存储postgresql当前连接个数

postgres=# \d pg_stat_activity
视观表 "pg_catalog.pg_stat_activity"
栏位 | 型别 | 修饰词
------------------+--------------------------+--------
datid | oid |
datname | name |
pid | integer |
usesysid | oid |
usename | name |
application_name | text |
client_addr | inet |
client_hostname | text |
client_port | integer |
backend_start | timestamp with time zone |
xact_start | timestamp with time zone |
query_start | timestamp with time zone |
state_change | timestamp with time zone |
waiting | boolean |
state | text |
query | text |