How to Delete a PostgreSQL Database

In PostgreSQL, version upgrading is performed in different ways: Installing packages with a new version of PostgreSQL. It is suitable only for minor updates. Before performing the update, study the release notes; Using the standard pg_dumpall program. It is a reliable method, but there may be a long downtime. Using the standard pg_upgrade program. Another quick way to upgrade, but errors may occur. Updating via logical replication. This option has minimal downtime but is only suitable for PostgreSQL versions greater than 10.0. Earlier versions require extensions. The choice depends on which release is used on the server and which version you want to upgrade to. In this article, we will look at all the above upgrade methods. If you have some troubles while using PostgreSQL, check our instruction on how to set up your database. Important notes before upgrading The main thing is to understand the peculiarities of updates between different versions. The numbers consist of two digits, for example, 10.1. The first digit is the major version number (10). The second digit is the minor release number (1). Before PostgreSQL 10, the version numbers consisted of three digits. For example, in 9.6.3, 9.6 is the major release number and 3 is the minor version number. You must understand this difference to choose the right upgrade method. In minor versions, the data storage format does not change, so there are no compatibility problems. Therefore, the transition from PostgreSQL 10.1 to 10.6 can be carried very easily. To upgrade, turn off the server, replace the executable files, and start the server again. However, the documentation notes that some releases may require manual changes. Therefore, always read the release notes before upgrading. In major versions, the data format may change. This makes updating more difficult. You need to either unload the data and upload it again, use the pg_upgrade program, or use logical replication. We'll talk about all these methods below. Upgrading within one major version Let's look at how to update Postgresql Version 14.1 to PostgreSQL 14.3 on an Ubuntu server. PostgreSQL is available on Ubuntu by default. Start with the command: sudo apt-get upgrade Debian and Ubuntu only release one version of PostgreSQL per OS release. For example, Debian Squeeze/6.0 only has PostgreSQL 8.4. If you need a different version of PostgreSQL, use packages from PGDG. If you want the latest version of PostgreSQL, you must first install the Postgres repository. Add a repository: sudo sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt $(lsb_release -cs)-pgdg main" > /etc/apt/sources.list.d/pgdg.list' Import the signing key: wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add - Update the list of packages in the system: sudo apt-get update Install the required Postgres version: sudo apt-get -y install postgresql-14.3 To view the list of installed DBMSs, run: dpkg --get-selections | grep postgres Also see the list of clusters: pg_lsclusters Stop PostgreSQL before making changes: sudo service postgresql stop When Postgres packages are installed, they create a default cluster for you. You should rename the new Postgres cluster so there are no conflicts with the old cluster name when upgrading. sudo pg_renamecluster 14.3 main main_pristine Upgrade the old cluster: sudo pg_upgradecluster 14.1 main Start the service: sudo service postgresql start Check the list of clusters again and make sure the new one is working: pg_lsclusters Get rid of the old cluster: sudo pg_dropcluster 14.1 main Upgrading via pg_dumpall If you need to change the major version, use the pg_dumpall program. The essence of this method is to unload data from one main version and then load it into another. Before unloading data, make sure that no changes are being made to the database right now. Otherwise, some of the changes may not be included in the final dump. Get the dump and write it to a file: pg_dumpall > output_file Stop the server: pg_ctl stop Change the name of the old directory to eliminate name conflicts: mv /usr/local/pgsql /usr/local/pgsql.old The old directory can simply be deleted. But it would be wiser to rename it to leave room for restoring data. Instead of /usr/local/pgsql, specify the path to your directory. Install the new version from source. There is a detailed guide in the documentation.  Form a new cluster: /usr/local/pgsql/bin/initdb -D /usr/local/pgsql/data Transfer all changes to the pg_hba.conf and postgresql.conf files. Start the database server: /usr/local/pgsql/bin/postgres -D /usr/local/pgsql/data Restore data from backup: /usr/local/pgsql/bin/psql -d postgres -f output_file The disadvantage of this method is that the server will be turned off for a long time. To reduce downtime, you can install the new server in a different directory and then run the old and new servers on different ports. To transfer data, use the command: pg_dumpall -p 5432 | psql -d postgres -p 5433 Instead of 5432 and 5433, specify the port numbers on which you ran the servers. Upgrading via pg_upgrade To avoid unloading and uploading data, use the pg_upgrade program. It helps you update faster. The pg_upgrade program creates system tables anew, taking into account changes in the PostgreSQL latest versions. In this case, the old data files are retained. In addition, pg_upgrade verifies that the clusters are compatible. The pg_upgrade program helps you upgrade from PostgreSQL 8.4.X to the current DBMS release. Let's look at a general upgrade plan using pg_upgrade. Move the old cluster. This must be done if the directory was not linked to the old release. For example, it is located at /usr/local/pgsql. If you do not rename it, a conflict will occur during the update. Renaming is performed when the server is turned off with the command: mv /usr/local/pgsql /usr/local/pgsql.old Build a new version from source. Adjust configure so that the flags are compatible with the old cluster configuration. Before starting the upgrade, pg_upgrade will check the compatibility of the flags. Install new executable files. To place the server in a non-standard directory, use prefix: make prefix=/usr/local/pgsql.new install Use initdb to initialize a new cluster. Check that the flags are compatible with the flags of the old cluster. Install extension shared object files. If updates are available, pg_upgrade will automatically create a script for their subsequent installation. Transfer full text search files. Configure peer authentication in pg_hba.conf. This needs to be done because pg_upgrade will connect to the old and new hosts multiple times. Check that the old and new servers are stopped: pg_ctl -D /opt/PostgreSQL/9.6 stoppg_ctl -D /opt/PostgreSQL/14 stop Run pg_upgrade from the new server. First, call the program in check mode by adding the flag: pg_upgrade --check In response, you will receive a list of adjustments that need to be made manually after the upgrade. If you made changes to the pg_hba.conf file, restore it to its previou state. Sometimes, other configurations on the new cluster need to be changed to match the settings of the old cluster. Start the server. If you are satisfied with the result, delete the old cluster. For details and features of using pg_upgrade, see the documentation. Using Logical Replication Starting from the 10th version of PostgreSQL, we have a method for logical replication of data objects and changes in them. It is based on the use of replication identifiers; usually, they are primary keys. Logical replication uses the publish-subscribe model. The user creates a snapshot of the published database and copies it to the subscriber. In the PostgreSQL documentation, one of the typical scenarios for using logical replication is precisely the replication between different major versions of PostgreSQL. The backup server can be located on the same or different host. After synchronization is complete, various options are available. For example, you can make the new server the main one and turn off the old one. The main advantage of logical replication is minimal downtime. Server interruption, in some cases, is limited to a few seconds. Conclusion We looked at universal methods for upgrading PostgreSQL to a new major version and updating within one major version. Using this guide, you can select the method that works best for your particular case and update your current version of PostgreSQL. Hostman provides pre-configured and ready-to-use cloud databases, including cloud PostgreSQL. Frequently Asked Questions How to check PostgreSQL version on my server? You can run psql --version in the terminal or connect to your DB and run SELECT version();. How do I upgrade PostgreSQL to a new version? Use pg_dumpall to back up, install the new version, and restore your data. What is the difference between pg_upgrade and pg_dump? pg_upgrade is quicker and keeps configs. pg_dump is better if you want full control. Do I need to uninstall the old PostgreSQL version? Nope, you can keep both temporarily to ease migration.

When working with PostgreSQL, you might eventually need to transfer a database from one server to another. Despite seeming complex, PostgreSQL migration can be accomplished using PostgreSQL's built-in tools. This article outlines various methods to transfer a PostgreSQL database from one server to another on Ubuntu 22.04. Prerequisites To migrate a Postgres database, you will need: A current server running Ubuntu 22.04 with PostgreSQL installed. The database to be transferred should already exist in PostgreSQL. A new cloud server or virtual machine with Ubuntu 22.04 and affordable cloud PostgreSQL pre-installed. This article uses PostgreSQL version 15. On Hostman, you can easily deploy such a server by choosing the PostgreSQL image when creating a server. Optionally, the pgAdmin client application for connecting and managing PostgreSQL databases. PgAdmin can be installed on any OS, including Windows, Linux, and macOS. Preparation Before Database Transfer Before starting the Postgres migration, ensure that both servers have: A network connection between them. Use tools like ping and telnet to verify this (with telnet, check ports 22 and 5432). Ports 22 (SSH) and 5432 (PostgreSQL) open. Enough free disk space. Configuring PostgreSQL for Remote Connections Ensure PostgreSQL can accept remote connections on both servers: Edit the postgresql.conf file. If using a different version, replace 15 with your version number: nano /etc/postgresql/15/main/postgresql.conf Find the listen_addresses parameter. By default, it is commented out and accepts only local connections (localhost). Allow remote connections from specific addresses or all addresses (for testing purposes, use *): listen_addresses = '*' In production environments, specify only the required addresses.  Save and exit the file. Edit the pg_hba.conf file: nano /etc/postgresql/15/main/pg_hba.conf Find the line for IPv4 local connections (# IPv4 local connections) and update it to allow connections from specific addresses or all addresses for testing: host all all 0.0.0.0/0 md5 Save and exit the file. Restart the PostgreSQL server: systemctl restart postgresql Set a strong password for the PostgreSQL user on both servers: sudo -i -u postgres psql In the psql console run: ALTER USER postgres WITH PASSWORD 'nsH7z*0kl>&7?7'; Where postgres is the username and nsH7z*0kl>&7?7 is the password. Transferring the Database Using pg_dump and psql Typically, transferring a database involves three steps: Creating a backup of the database. Transferring the backup to the target server. Restoring the database on the new server. These steps can be performed using PostgreSQL's pg_dump and psql tools. Transferring a Database For instance, let's look at transferring a database named e_commerce from a server with IP 166.1.227.252 to a server with IP 91.206.179.207. Create the target database beforehand: CREATE DATABASE e_commerce; Then run: pg_dump -h localhost -U postgres e_commerce | psql -h 91.206.179.207 -U postgres e_commerce Explanation: pg_dump creates a backup of the database. -h localhost specifies the database server address. -U postgres specifies the username. e_commerce is the database name on the current and new server.  psql connects to the remote PostgreSQL server and loads the database. -h 91.206.179.207 specifies the target server address. Transferring Without Remote Access If remote access is unavailable, save the database to a file, transfer it using scp, and restore it on the target server: pg_dump -h localhost -U postgres e_commerce > e_commerce.sql && scp e_commerce.sql db-admin@91.206.179.207:/var/lib/postgresql When executing the command, the password for the postgres system user will be requested, not the password for the postgres user defined within the database. Where: pg_dump creates a database backup; -h localhost is the address of the server (IP address or domain name) where the database is located. In this example, the database server address matches the server address itself. If the database is on another server and network access is available, you can specify the address of the remote database; -U postgres is the username used to connect to the database; e_commerce is the name of the database to be transferred; e_commerce.sql is the name of the file in .sql format where the database will be saved; scp is a utility for secure file copying between hosts. It uses the SSH protocol for data transfer and protection; db-admin@91.206.179.207:/var/lib/postgresql means username_on_remote_server@address_of_remote_server:full_path where the backup file will be saved. After entering the command, you first need to enter the password for the database user account (in this example, it is the postgres user), and then enter the password for the remote server user (in this example, it is the db-admin user). Now you need to upload the file to the database. Run these commands on the target server. Create a database in psql: CREATE DATABASE e_commerce; Then, exit psql and run in the terminal: psql e_commerce < e_commerce.sql Creating a Compressed Archive For larger databases, create a compressed archive: pg_dump -h localhost -U postgres e_commerce > e_commerce.tar.gzip && scp e_commerce.tar.gzip db-admin@91.206.179.207:/var/lib/postgresql Restore from the archive: psql e_commerce < e_commerce.tar.gzip Adding a Timestamp to the Archive Name If you need to know the exact date and time that the database was backed up, you can include it in the name of the file being created.  To do this, use the date command and the date format. The example below will use the day-month-year date format: pg_dump -h localhost -U postgres e_commerce > e_commerce_$(date +%d-%m-%y).sql Transferring the Database Using pgAdmin Alternatively, you can use pgAdmin's graphical interface for the Postgres database migration. Backup Database Launch pgAdmin: Open pgAdmin and connect to your PostgreSQL server. Register Server: Right-click on Object Explorer, select Register, then Server. Configure Connection: Name: In the General tab, enter a name for the connection (e.g., my_db). Next, go to the Connection tab and specify: Host name/address: Specify the IP address or domain name of the PostgreSQL server. Port: Default is 5432; change if needed. Maintenance database: Name of the database for backup. Username and Password: Enter credentials for database access. Connect: Click Save to connect. If successful, the database appears on the left sidebar. Backup Database: Right-click on the database name and select Backup.   Set a Filename for the backup file. Choose a Format and Encoding (UTF8 recommended). Select specific Objects to include. Click Backup to start. Restore Database Prepare New Database: Open psql shell. Execute: CREATE DATABASE e_commerce; Connect to PostgreSQL Server: In pgAdmin, connect to the new PostgreSQL server, selecting e_commerce as the database. Restore Database: Right-click on the database name and choose Restore. Set the Format (ensure it matches the backup file). Specify the Filename of the backup file. Click Restore to begin. Wait for the Process completed confirmation. Conclusion PostgreSQL offers several methods to migrate databases between servers, including using built-in tools for flexible and robust database backups and transfers. If you've ran into some troubles, check our instruction on how to create server on Ubuntu.

PostgreSQL is an advanced open-source relational database management system (DBMS). There are two ways to install it on Debian 11: from the operating system repository or the official PostgreSQL repository. In this article, you will learn both methods, as well as how to perform common operations like creating roles and databases. Don't forget to check how to configure static IP address on Debian. Installation from the Debian 11 repository On Debian, you can install PostgreSQL directly from the system repository. First, update your package list. Launch the terminal and run: sudo apt update && sudo apt upgrade The PostgreSQL package is available in the Debian repository, so you can install it using the apt utility. To do this, run: sudo apt install postgresql postgresql-contrib Once the installation is complete, check the status of the service using the command: sudo systemctl status postgresql If the service does not start automatically, you can start it manually. To do this, run: sudo systemctl start postgresql To stop a running service, run: sudo systemctl stop postgresql Before configuring PostgreSQL on Debian, make sure the service is running. Installation from the official PostgreSQL repository If you want to use only the latest versions of Postgres, we recommend using the official PostgreSQL repository for installation and subsequent updates. First of all, you need to add the GPG signing key. This is a security requirement to verify the authenticity of the PostgreSQL repository. To do this, launch a terminal and run: curl -fsSL https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo gpg --dearmor -o /usr/share/keyrings/postgresql-keyring.gpg Now you are ready to add the Postgres repository. Use the following command: echo "deb [signed-by=/usr/share/keyrings/postgresql-keyring.gpg] http://apt.postgresql.org/pub/repos/apt/bulseye-pgdg main" | sudo tee /etc/apt/sources.list.d/postgresql.list After successfully integrating the PostgreSQL library, you can install the DBMS. But before you do that, update the system repository using the command: sudo apt update After updating, run the following command to install PostgreSQL on Debian: sudo apt install postgresql Installation is completed. Now you can proceed to the basic configuration of PostgreSQL. Basic setup When installing Postgres, the postgres user is automatically created. You can use this account for your first connection. Switch to the postgres user: sudo su - postgres Run the psql utility which is a shell for managing PostgreSQL: psql You can now interact with the PostgreSQL server. To exit the shell, enter: \q You can use the following command to access the Postgres command line without switching users: sudo -u postgres psql However, the postgres user is usually only used from localhost. If, for example, you use cloud databases, it is better to create a new role for the connection. Creating a role and a database The createuser command allows you to create new roles from the command line. Only superusers and roles with CREATEROLE privileges can create new roles. In the following example, we will create a new role named hostman and a database named hostman_db, and then grant the new role privileges to manage the database. First create a new role: sudo su - postgres -c "createuser hostman" Then create a new database: sudo su - postgres -c "createdb hostman_db" To grant the user permissions to the database, connect to the shell: sudo -u postgres psql Run the following query to grant the hostman user privileges to manage the hostman_db database: GRANT ALL PRIVILEGES ON DATABASE hostman_db TO hostman; You can create new roles and databases in the PostgreSQL shell. In this case, the syntax will be slightly different. To create a new role with a password, run: create user cloud with password 'hostmancloud'; To create a new database, run: create database cloud_db; Then you must also grant all privileges with the GRANT ALL PRIVILEGES ON DATABASE … TO … command. Setting up remote access By default, the Postgres server only listens on the local interface 127.0.0.1. This may be inconvenient. Let's say you have a server on Hostman with PostgreSQL installed. It will be much more convenient to connect to it remotely. To do this, you need to configure the server to listen to other network interfaces. To change the configuration, open the postgresql.conf file using any editor. This example uses the nano editor: sudo nano /etc/postgresql/12/main/postgresql.conf Find the CONNECTIONS AND AUTHENTICATION section and the line #listen_addresses = 'localhost' in the configuration file. Change the line value to listen_addresses = '*'. If you want the server to listen not to all network interfaces, but only to the selected one, specify it instead of an asterisk. Save the file and restart the Postgres service for the changes to take effect: sudo service postgresql restart The last step is to allow connections from the network. To install it, you need to edit the pg_hba.conf file. Open it in the editor: sudo nano /etc/postgresql/12/main/pg_hba.conf Find the IPv4 local connections line. Specify the desired network. For example, like this: TYPE DATABASE     USER ADDRESS                  METHOD host all hostman 38.62.228.244  md5 You can use other authentication methods. For a complete list, see the PostgreSQL documentation. Conclusion There are two ways to install managed PostgreSQL on Debian. The first option is to use the system repository. Its main advantage is speed. There is no need to install anything additional, just run one command. The downside is that the system repository does not always contain the latest version of the software. The second installation option is to use the official PostgreSQL repository. This method ensures that you are using the latest version of the DBMS. But you will have to perform a few more steps: first, add the official repository itself and only then install Postgres from it.