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

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

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

PostgreSQL Pgbadger Installation On Linux

-
Image
PgBadger is a tool that analyzes PostgreSQL log files and generates reports on execution of SQL and server operation. Statistical reports analyzed from a number of perspectives can be useful not only for grasping the usual database operation but also as a hint for performance improvement. The report output by pgBadger has the following features. Graph output in HTML format Many statistical objects Daily, Weekly unit creation possible 1.Graph output in HTML format Many of the analysis results can be displayed in graph form by outputting the report in HTML format (output in text format or JSON format is also possible). By analyzing the log information graphed, it is much more prospective for people to see than the raw log data. So, if you do not need to handle it with another tool separately, we recommend report output in HTML format. 2.Many statistical objects A lot of data useful for database performance analysis is output in the report as shown below. Qu
Read more

7 Steps to configure BDR replication in postgresql

-
Image
 The  BDR  (Bi-Directional Replication) project adds multi-master replication to PostgreSQL 9.4.  Postgres-BDR has a lower impact on the masters(s) than trigger-based replication solutions. There is no write-amplification, as it does not require triggers to write to queue tables in order to replicate writes.   Here We are using  postgres version 9.4.12 and bdr version 1.0.2. for configuring  multi master replication . Simply Following 7 steps you can configure the multi master replication in postgresql. To download the bdr in below link. .   https://github.com/2ndQuadrant/bdr/archive/bdr-pg/REL9_4_12-1.tar.gz $ tar -xzvf REL9_4_12-1.tar.gz $ wget https://github.com/2ndQuadrant/bdr/archive/bdr-plugin/1.0.2.tar.gz $ tar -xzvf 1.0.2.tar.gz 1. To install BDR. $ cd ~/bdr-bdr-pg-REL9_4_12-1 $ ./configure --prefix=/usr/lib/postgresql/9.4 --enable-debug --with-openssl $ make -j4 -s install-world $ cd ~/bdr-bdr-plugin-1.0.2 $ PATH=/usr/lib/postgresql/9.4/bin:"$PATH" ./c
Read more

How To Schedule PostgreSQL Jobs using pgAgent on Linux plateform

-
Image
Taking regular SQL database backup is one of the most important responsibilities of a database administrator. By setting up automatic database backup we can get rid of the additional overhead of doing it manually, every day, week or month. When it comes to PostgreSQL running in any Unix distributions or in Windows, there are at least two ways to do it. Using the built in CronJobs/ CronTabs in case of  Linux, and Windows scheduled tasks in Windows . Using PostgreSQL’s own scheduling agent,  pgAgent . Often DBAs tends to rely on CronTabs or Scheduled tasked because of the ease of use it offers. But there are several advantages if you use pgAgent instead. Though it takes a little effort to install pgAgent, it is much better than Cron jobs or Scheduled tasks. Why use pgAgent over CronJob: Compared to CronTab, PgAgent has the following advantages:  You can have multiple steps for a job without having to resort to a batch script. You can have multiple schedules for a job
Read more