How to show current schema of running queries in postgresql 13

[陈锡汉]

Hello,I use multi-schemas in one database in Postgres,such as

```
Postgres(instance)
 MyDB
   public
   MySchema1
     table1
     table2
   MySchema2
     table1
     table2
   MySchema3
     table1
     table2
```

And It's open to my users,my users will run queries,
such as
User1:
```
set search_path=MySchema1;
select * from table1,table2;
```

User2:
```
set search_path=MySchema2;
select * from table1,table2;
```

User3:
```
set search_path=MySchema3;
insert into table3 select * from MySchema1.table1,MySchema2.table2;
select * from table3;
```

I want to show current schema of running queries,But pg_stat_activity can only 
show database name, not schema name.

I want current schema (search_path ) as

| datname  | username | schema   | query   |
| -------- | -------- | -------- | -------- |
| MyDB     | User1    | MySchema1  | select * from table1,table2;  |
| MyDB     | User2    | MySchema2  | select * from table1,table2;  |
| MyDB     | User3    | MySchema3  | insert into table3 select * from 
MySchema1.table1,MySchema2.table2;  |

Is there any sys views can do it?

Thank you!
Best regards,
CavonChen