As autonomus transactions are not avaliable in postgres we are using dblink as a workaroud but there is a scenerio which is as
linked from Does Postgres support nested or autonomous transactions?
select * from dblink_connect('TEST1','host=localhost port=5432 dbname=tyguy user=postgres password=postgres') as t1(text);
Then when we use the method
SELECT dblink_get_connections();
then only one connection is visible that is absolutely correct named as 'TEST1'
but when i open a new pg admin window or a new session then the same is not avaliable as
SELECT dblink_get_connections();
returns empty. No connection of name 'TEST1'
I am confused is DBlink is at database level ? or session level .
if it is at session level then how many dblink named connections can be opened in a database.
Related
I have a AWS RDS PostgreSQL 13 server with some databases. I have to create an empty copy of one database (empty means schema (tables, views, functions) + security (users, roles)).
Is pg_dump -s what I am looking for?
Thanks!
pg_dump -d db_name -s. You will also need to do pg_dumpall -g to get the global data e.g. roles. This will get all global data for the Postgres cluster, so you may have more then you need for the particular database.
Postgres allows the use of any existing database on the server as a template when creating a new database. I'm not sure whether pgAdmin gives you the option on the create database dialog but you should be able to execute the following in a query window if it doesn't:
CREATE DATABASE newdb WITH TEMPLATE originaldb OWNER dbuser;
Still, you may get:
ERROR: source database "originaldb" is being accessed by other users
To disconnect all other users from the database, you can use this query:
SELECT pg_terminate_backend(pg_stat_activity.pid) FROM pg_stat_activity WHERE pg_stat_activity.datname = 'originaldb' AND pid <> pg_backend_pid();
I'm a bit confused about why I can't drop my database, so after connecting to my rds postgres instance with
psql --host=mu_user.amazonaws.com --port=5432 --username=my_user --password --dbname=postgres
I've REVOKED new connection to the db I want to drop with
REVOKE CONNECT ON DATABASE mydb FROM public;
then I have terminated all connection with
SELECT pid, pg_terminate_backend(pid)
FROM pg_stat_activity
WHERE datname = 'mydb' AND pid <> pg_backend_pid();
after that when I want to drop the db I still can't because It will say
ERROR: database "mydb" is being accessed by other users
DETAIL: There are 10 other sessions using the database.
If I inspect live connections with
SELECT
pid
,datname
,usename
,application_name
,client_hostname
,client_port
,backend_start
,query_start
,query
,state
FROM pg_stat_activity
WHERE state = 'active';
there will be none, but if I change active to idle I can see a bunch, and after trying to kill them with pg_terminate_backend(pid) I again can't drop the db and I again have the same ERROR, so can someone please help me understand what I'm I doing wrong here?
Those connections which are idle and always appearing are by my_user, who is also a superuser.
The problem is that those other connections are by a superuser, and superusers are exempt from permission checks, so revoking the CONNECT privilege on the database won't keep these guys out.
You could either block the connections via pg_hba.conf, or you can run both statements immediately after each other:
SELECT pg_terminate_backend(pid) FROM pg_stat_activity; DROP DATABASE mydb;
in the hope that the users won't have time to reconnect before the DROP DATABASE hits.
I'm trying to drop the database I'm currently connected to like so, but I'm getting this error:
pq: cannot drop the currently open database
I don't really understand how I'm expected to drop the database if I have to close my connection, because then I don't think I will be able to use dbConn.Exec to execute my DROP DATABASE statement?
dbConn *sql.DB
func stuff() error {
_, err := dbConn.Exec(fmt.Sprintf(`DROP DATABASE %s;`, dbName))
if err != nil {
return err
}
return dbConn.Close()
}
I guess I could connect to a different database and then execute it on that connection, but I'm not even sure if that'd work, and it seems really weird to have to connect to a new database just to drop a different database. Any ideas? Thanks.
Because, you are trying to execute dropDb command on database, to which you have open connection.
According to postgres documentation:
You cannot be connected to the database you are about to remove. Instead, connect to template1 or any other database and run this command again.
This makes sense, because when you drop the entire database, all the open connection referencing to that database becomes invalid, So the recommended approach is to connect to different database, and execute this command again.
If you are facing a situation, where a different client is connected to the database, and you really want to drop the database, you can forcibly disconnect all the client from that particular database.
For example, to forcibly disconnect all clients from database mydb:
If PostgreSQL < 9.2
SELECT pg_terminate_backend(procpid) FROM pg_stat_activity WHERE datname = 'mydb';
Else
SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE datname = 'mydb';
Note: This command requires superuser privileges.
Then, you can connect to different database, and run dropDb command again.
If you encounter this problem in IntelliJ, change the schema with the following dropdown to postgres.
After that, I was able to drop a db.
I am using PostgreSQL 12 and pgAdmin-4 in Windows 10. I had to use a combination of the above answers to drop a database, which I could not drop in pgAdmin because I was unable to close all open connections in pgAdmin.
Close pgAdmin-4.
In Windows command line, assuming my server's name is postgres and my database is mydb:
C:\> psql -U postgres
I logged in with my server password.
I then closed all open connections to mydb:
postgres-# SELECT * FROM pg_stat_activity WHERE pg_stat_activity.datname='mydb';
postgres-# SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE datname = 'mydb';
Finally, I successfully dropped mydb:
postgres-# DROP DATABASE mydb;
Now if I go back into pgAdmin-4 it is gone.
To drop the database:
\c postgres
Then
DROP DATABASE your_database works
It's simple, just connect to another database \c database2. Once connected execute the drop database command while connected to the other database.
Just Connect to a different database using \c db_name;
and then drop the required database using drop database db_name;
If you are using DBeaver make sure you are not connected to the database you are trying to drop. Go to edit connections and look at the database name.
Switch the connection to a different database and then drop the database you wish.
None of this worked for me since I tried to do it through pgAdmin which kept database connections open as soon as I delete them.
Solution:
C:\Program Files\PostgreSQL\11\scripts\runpsql.bat
after you supply correct information you will be able to get pg command prompt, here you can just type:
dbdrop yourdatabase
After that you might still see database in pgAdmin but now you can just simply delete it with right click and DELETE/DROP option.
you can force to drop database with: DROP DATABASE mydb WITH (FORCE)
We got a Postgres database credentials (with SSL on) from our contractor, which allow us to connect to the DB using pdAdmin 3. The DB is read-only (can't do pg_dump) to us and basically the contractor will not grant us more privileges.
We need to fetch some data from this remote DB to our local DB. So I wanted to use dblink to perform this task.
I run this on psql:
insert into shifts select * from dblink('hostaddr=remote_addr port=9000 dbname=production user=user password=passwd', 'select user_id, location_id from shifts') as t1(user_id integer, location_id integer);
Then I got:
ERROR: password is required DETAIL: Non-superuser cannot connect if
the server does not request a password. HINT: Target server's
authentication method must be changed.
Since I am new to Postgres and dblink, I have no idea why it is complaining there is no password. And I wonder, to do a dblink connection, does the remote database needs to grant any more privileges?
If the pdAdmin 3 is able to connect to the remote DB with the credentials, what should I do to make dblink work?
Thanks!
Yes only superuser can provide you to the facility to connect through DBLINK
just run this command below whether you are able to connect to database
SELECT dblink_connect('myconn', 'dbname=postgres');
SELECT dblink_connect('myconn', 'hostaddr=remote_addr port=9000 dbname=production user=user password=passwd');
just give the name of database u want to connect after dbname
You can connect
dblink_connect_u
dblink_connect_u() is identical to dblink_connect(), except that it
will allow non-superusers to connect using any authentication method.
Link on postgres site is
dblink
For Superuser ask them to create extension
CREATE EXTENSION dblink;
for your database or schema .
I'm trying to rename a database in my Redshift cluster.
You cannot rename the database when you're connected to it so I've created a temporary database, reconnected with SQL Workbench to the temporary db and issued:
ALTER DATABASE olddb RENAME to newdb;
I get an error stating ERROR: database "olddb" is being accessed by other users [SQL State=55006]
I've checked who is connected and there appear to be some connections from user rdsdb to the database. I assume this is a service account that AWS Redshift use to perform maintenance tasks etc.
How can I rename the database when this superuser is connected?
Many thanks.
You cannot alter the name of (or delete!) the database that is created during the initial cluster creation. I don't believe this is mentioned in the docs but I've confirmed it with them.
We can change the database name which is already created.
Detailed steps on how to do
Connect to the old database and create a new database if you do not have another one already.
create database databasebasename
In this example, I will call the databasename as 'newdb'.
Connect to newdb using connecting string as, jdbc:redshift://.us-east-1.redshift.amazonaws.com:8192/newdb, with the same password and username of your superuser (or the other eligible users as mentioned above).
Now you can alter the database name. Substitute 'database_name_new' with the desired databasename.
alter database old-db-name rename to database_name_new;
If there are any active sessions, you'll have to kill them. To find the pid of active sessions:
select * from STV_SESSIONS where user_name='rdsdb';
Then to kill a session:
SELECT
pg_terminate_backend(<pid>)
FROM
pg_stat_activity
WHERE
-- don't kill my own connection!
procpid <> pg_backend_pid()
-- don't kill the connections to other databases
AND datname = '<old-db-name>';
Once complete, you can connect back to that new database using the new name in the connection string as
jdbc:redshift://<cluser-id>.us-east-1.redshift.amazonaws.com:8192/database_name_new
You can delete the temporary 'newdb'.
drop database databasebasename
That's possible now -- I just renamed the database that was created during the initial cluster creation.
We had a similar situation.
Step 1: Connect to the database which is not the one you are trying to rename. Check the same by executing SELECT CURRENT_DATABASE();.
Step 2: Execute the query below -
SELECT
ss.*, 'select pg_terminate_backend('||process||');'
FROM
stv_sessions ss
ORDER BY
db_name;
The output of the query will have a column at the end with the select statements. Execute those to kill the sessions.
Step 3(Optional): If you are not the owner of the database try to modify the ownership of the database -
ALTER DATABASE <database to be renamed>
OWNER TO <user which is going to do the rename>;
Step 4: Rename the database