Drop Down MenusCSS Drop Down MenuPure CSS Dropdown Menu

Terminate Postgresql Sessions

-
This blog post is based on a PostgreSQL 9.1 version.
problems:-
Sometimes you need to terminate connections initiated by badly behaving client application, or just make sure nobody is querying database during a major update.
The solution is to use pg_stat_activity view to identify and filter active database sessions and then use pg_terminate_backend function to terminate them.
To prevent access during an update process or any other important activity you can simply revoke connect permission for selected database users or alter pg_database system table.

Who is permitted terminate connections:-
Every database role with superuser rights is permitted to terminate database connections.

How to display database sessions
pg_stat_activity system view provides detailed information about server processes.
SELECT datname as database,
      procpid as pid,
      usename as username,
      application_name as application,
      client_addr as client_address,
      current_query
 FROM pg_stat_activity

Sample output that will be used in the following examples.
database | pid  | username | application | client_address |                                                                           current_query
----------+------+----------+-------------+----------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------
blog     | 8603 | blog     | blog_app    | 192.168.3.11   | select * from posts order by pub_date
postgres | 8979 | postgres | psql        |                | select datname as database,procpid as pid,usename as username,application_name as application, client_addr as client_address, current_query from pg_stat_activity
wiki     | 8706 | wiki     | wiki_app    | 192.168.3.8    |
(3 rows)


How to terminate all connections to the specified database
Use the following query to terminate all connections to the specified database.
SELECT pg_terminate_backend(procpid)
 FROM pg_stat_activity
WHERE datname = 'wiki'

Comments

Post a Comment

Popular posts from this blog

AWS Account Creation

-
Image
Amazon provides a fully functional free account for one year for users to use and learn the different components of AWS. You get access to AWS services like EC2, S3, DynamoDB, etc. for free. However, there are certain limitations based on the resources consumed. Step 1  − To create an AWS account, open this link  https://aws.amazon.com  and sign-up for new account and enter the required details. If we already have an account, then we can sign-in using the existing AWS password. Step 2  − After providing an email-address, complete this form. Amazon uses this information for billing, invoicing and identifying the account. After creating the account, sign-up for the services needed. Step 3  − To sign-up for the services, enter the payment information. Amazon executes a minimal (exactly 2 rupees indian cost) amount transaction against the card on the file to check that it is valid. This charge varies with the region. Step 4  − Next, is the identity verification. Amazon does
Read more

postgreSQL Upgradation combination server

-
combination of these two resources: https://gist.github.com/tamoyal/2ea1fcdf99c819b4e07d and http://www.gab.lc/articles/migration_postgresql_9-3_to_9-4 The  second  one  helped more  then the first one. Also to not, don't follow the steps as is as some are not necessary. Also, if you are not being able to backup the data via postgres console, you can use alternative approach, and backup it with pgAdmin 3 or some other program, like I did in my case. Also, the link:  https://help.ubuntu.com/stable/serverguide/postgresql.html  Helped to set the encrypted password and set md5 for authenticating the postgres user. After all is done, to check the postgres  server  version run in terminal: sudo - u postgres psql postgres After entering the password run in postgres terminal: SHOW SERVER_VERSION ; It will output something like: server_version ---------------- 9.4.5 For setting and starting postgres I have used command: > sudo bash # root > su postgres #
Read more

How to find the server is whether standby (slave) or primary(master) in Postgresql replication ?

-
Method 1 You can check the mode of the server using "pg_controldata". [pgsql@test~]$ pg_controldata /usr/local/pgsql/data84/ Database cluster state: in archive recovery --> This is Standby Database Database cluster state: in production --> This is Production Database [Master] Method 2 You can use pg_is_in_recovery() which returns True if recovery is still in progress(so the server is running in standby mode or slave) postgres=# select pg_is_in_recovery(); pg_is_in_recovery ------------------- t (1 row) If Return    false   so the server is running in primary mode or master postgres=# select pg_is_in_recovery(); pg_is_in_recovery ------------------- f (1 row)
Read more

How to Return a Result Set from a PostgreSQL Stored Procedure

-
Image
Both stored procedures and user-defined functions are created with CREATE FUNCTION statement in PostgreSQL. To return one or more result sets (cursors in terms of PostgreSQL), you have to use  refcursor  return type. Quick Example : -- Procedure that returns a single result set (cursor) CREATE OR REPLACE FUNCTION show_cities ( ) RETURNS refcursor AS $$ DECLARE ref refcursor; -- Declare a cursor variable BEGIN OPEN ref FOR SELECT city , state FROM cities; -- Open a cursor RETURN ref; -- Return the cursor to the caller END ; $$ LANGUAGE plpgsql; Overview : Return Multiple Result Sets Cursor Lifetime Until the  end  of transaction Auto-commit Must be  off Transaction must be active so the caller can see a result set Important Note : The cursor remains open until the end of transaction, and since PostgreSQL works
Read more

How to Get Table Size, Database Size, Indexes Size, schema Size, Tablespace Size, column Size in PostgreSQL Database

-
In this post, I am sharing few important function for finding the size of database, table and index in PostgreSQL. Finding object size in postgresql database is very important and common. Is it very useful to know the exact size occupied by the object at the tablespace. The object size in the following scripts is in GB. The scripts have been formatted to work very easily with PUTTY SQL Editor. 1. Checking table size excluding table dependency: SELECT pg_size_pretty(pg_relation_size('mhrordhu_shk.mut_kharedi_audit')); pg_size_pretty ---------------- 238 MB (1 row) 2. Checking table size including table dependency: SELECT pg_size_pretty(pg_total_relation_size('mhrordhu_shk.mut_kharedi_audit')); pg_size_pretty ---------------- 268 MB (1 row) 3. Finding individual postgresql database size SELECT pg_size_pretty(pg_database_size('db_name')); 4. Finding individual table size for postgresql database -including dependency index: SELECT pg_size_pretty(pg_total_rel
Read more