Truncating all tables in a Postgres database

Question

I regularly need to delete all the data from my PostgreSQL database before a rebuild  How would I do this directly in SQL   At the moment I ve managed to come up with a SQL statement that returns all the commands I need to execute    SELECT  TRUNCATE TABLE       tablename        FROM pg tables WHERE tableowner  MYUSER     But I can t see a way to execute them programmatically once I have them

User · Answer

Guys the better and clean way is to    1  Create Schema dump of database  --schema-only  pg dump mydb -s   schema sql  2  Drop database drop database mydb   3  Create Database create database mydb   4  Import Schema psql mydb  lt  schema sql  It  s work for me   Have a nice day  Hiram Walker

User · Answer

FrustratedWithFormsDesigner is correct  PL pgSQL can do this  Here s the script   CREATE OR REPLACE FUNCTION truncate tables username IN VARCHAR  RETURNS void AS    DECLARE     statements CURSOR FOR         SELECT tablename FROM pg tables         WHERE tableowner   username AND schemaname    public   BEGIN     FOR stmt IN statements LOOP         EXECUTE  TRUNCATE TABLE      quote ident stmt tablename       CASCADE        END LOOP  END     LANGUAGE plpgsql    This creates a stored function  you need to do this just once  which you can afterwards use like this   SELECT truncate tables  MYUSER

User · Answer

Could you use dynamic SQL to execute each statement in turn  You would probably have to write a PL pgSQL script to do this   http   www postgresql org docs 8 3 static plpgsql-statements html  section 38 5 4  Executing Dynamic Commands

User · Answer

Explicit cursors are rarely needed in plpgsql  Use the simpler and faster implicit cursor of a FOR loop  Note  Since table names are not unique per database  you have to schema-qualify table names to be sure  Also  I limit the function to the default schema  public   Adapt to your needs  but be sure to exclude the system schemas pg   and information schema  Be very careful with these functions  They nuke your database  I added a child safety device  Comment the RAISE NOTICE line and uncomment EXECUTE to prime the bomb     CREATE OR REPLACE FUNCTION f truncate tables  username text    RETURNS void AS  func  DECLARE     tbl text      sch text  BEGIN    FOR  sch   tbl IN        SELECT schemaname  tablename       FROM   pg tables       WHERE  tableowner    username       AND         -- dangerous  test before you execute        RAISE NOTICE       -- once confident  comment this line           -- EXECUTE         --     and uncomment this one          format  TRUNCATE TABLE  I  I CASCADE    sch   tbl      END LOOP  END  func  LANGUAGE plpgsql   format   requires Postgres 9 1 or later  In older versions concatenate the query string like this   TRUNCATE TABLE      quote ident  sch            quote ident  tbl        CASCADE    Single command  no loop Since we can TRUNCATE multiple tables at once we don t need any cursor or loop at all   Passing table names in an array  Aggregate all table names and execute a single statement  Simpler  faster  CREATE OR REPLACE FUNCTION f truncate tables  username text    RETURNS void AS  func  BEGIN    -- dangerous  test before you execute     RAISE NOTICE       -- once confident  comment this line        -- EXECUTE         --     and uncomment this one    SELECT  TRUNCATE TABLE             string agg format   I  I   schemaname  tablename                     CASCADE     FROM   pg tables    WHERE  tableowner    username    AND    schemaname    public        END  func  LANGUAGE plpgsql   Call  SELECT truncate tables  postgres     Refined query You don t even need a function  In Postgres 9 0  you can execute dynamic commands in a DO statement  And in Postgres 9 5  the syntax can be even simpler  DO  func  BEGIN    -- dangerous  test before you execute     RAISE NOTICE       -- once confident  comment this line        -- EXECUTE         --     and uncomment this one     SELECT  TRUNCATE TABLE      string agg oid  regclass  text             CASCADE      FROM   pg class     WHERE  relkind    r   -- only tables     AND    relnamespace    public   regnamespace       END  func    About the difference between pg class  pg tables and information schema tables   How to check if a table exists in a given schema  About regclass and quoted table names   Table name as a PostgreSQL function parameter  For repeated use Create a  quot template quot  database  let s name it my template  with your vanilla structure and all empty tables  Then go through a DROP   CREATE DATABASE cycle  DROP DATABASE mydb  CREATE DATABASE mydb TEMPLATE my template  This is extremely fast  because Postgres copies the whole structure on the file level  No concurrency issues or other overhead slowing you down  If concurrent connections keep you from dropping the DB  consider   Force drop db while others may be connected

User · Answer

Just execute the query bellow  DO    DECLARE     r RECORD  BEGIN     FOR r IN  SELECT tablename FROM pg tables WHERE schemaname   current schema    LOOP         EXECUTE  TRUNCATE TABLE      quote ident r tablename             END LOOP  END

User · Answer

You can do this with bash also      bin bash PGPASSWORD    psql -h 127 0 0 1 -Upostgres sng --tuples-only --command  SELECT  TRUNCATE TABLE      schemaname            tablename        FROM pg tables WHERE schemaname in   cms test    ids test    logs test    sps test        tr    n         xargs -I   psql -h 127 0 0 1 -Upostgres sng --command        You will need to adjust schema names  passwords and usernames to match your schemas

User · Answer

In this case it would probably be better to just have an empty database that you use as a template and when you need to refresh  drop the existing database and create a new one from the template

User · Answer

If I have to do this  I will simply create a schema sql of current db  then drop  amp  create db  then load db with schema sql   Below are the steps involved   1  Create Schema dump of database  --schema-only   pg dump mydb -s  gt  schema sql  2  Drop database  drop database mydb   3  Create Database  create database mydb   4  Import Schema   psql mydb  lt  schema sql

User · Answer

Cleaning AUTO INCREMENT version   CREATE OR REPLACE FUNCTION truncate tables username IN VARCHAR  RETURNS void AS    DECLARE     statements CURSOR FOR         SELECT tablename FROM pg tables         WHERE tableowner   username AND schemaname    public   BEGIN     FOR stmt IN statements LOOP         EXECUTE  TRUNCATE TABLE      quote ident stmt tablename       CASCADE             IF EXISTS               SELECT column name              FROM information schema columns              WHERE table name quote ident stmt tablename  and column name  id            THEN            EXECUTE  ALTER SEQUENCE      quote ident stmt tablename       id seq RESTART WITH 1           END IF       END LOOP  END     LANGUAGE plpgsql

User · Answer

For removing the data and preserving the table-structures in pgAdmin you can do    Right-click database -  backup  select  Schema only  Drop the database Create a new database and name it like the former Right-click the new database -  restore -  select the backup  select  Schema only

User · Answer

If you can use psql you can use  gexec meta command to execute query output   SELECT     format  TRUNCATE TABLE  I  I   ns nspname  c relname    FROM pg namespace ns    JOIN pg class c ON ns oid   c relnamespace   JOIN pg roles r ON r oid   c relowner   WHERE     ns nspname    table schema  AND                               -- add table schema criteria      r rolname    table owner  AND                                 -- add table owner criteria     ns nspname NOT IN   pg catalog    information schema   AND    -- exclude system schemas     c relkind    r  AND                                           -- tables only     has table privilege c oid   TRUNCATE                          -- check current user has truncate privilege    gexec    Note that  gexec is introduced into the version 9 6

[postgresql] Truncating all tables in a Postgres database

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