How to Import and Export PostgreSQL Database

Introduction

PostgreSQL is the modern and most popular database management system now a day. Backing up PostgreSQL data is one of the most important tasks for any database administrator. It is an essential component of a data storage plan. Backups will help you to recover your system in the event of database corruption. PostgreSQL provides pg_dump and a pg_dumpall command-line utility to effectively backup your important information.

When working on a different project in different environments, you often need to export a database dump from one server and import it into another server. So it is essential to implement a backup strategy to protect against data loss.

In this post, we will show you how to import and export a PostgreSQL database using pg_dump, pg_dumpall, psql, and pg_restore utility.

Export a PostgreSQL Database with pg_dump Command

The pg_dump is a command-line tool that allows you to dump the content of a specified database into a single file. The pg_dump command provides several options that help you to specify tables or schemas to back up.

The basic syntax of the pg_dump command is shown below:

• -h Specify database server host

• -p Specify database server port

• -U Specify the user which is used to connect to the PostgreSQL database server

• -W Used to prompt for a password before connecting to the PostgreSQL server

• -d Specify the database to dump

• -F Specify one of the following output format files:

• p plain-text format

• c custom format

• d directory format

• t tar format

Examples:

To export a database named testdb into a plain-text format, run the following command:

pg_dump -U username -W -F p -d testdb > testdb.sql

To export a database named testdb into a tar format, run the following command:

pg_dump -U username -W -F t -d testdb > testdb.tar

To export a database named testdb into custom format, run the following command:

pg_dump -U username -W -F c -d testdb > testdb.dump

To export a database named testdb into a directory format, run the following command:

pg_dump -U username -W -F d -d testdb -f testdb-dir

If you want to export a large database and generate a smaller dump file, you can use the gzip tool with the pg_dump command to compress the dump file.

pg_dump -U username -W -F t -d testdb | gzip > testdb.tar.gz

Export All PostgreSQL Databases with pg_dumpall Command

The pg_dumpall is a command-line utility that allows you to export all PostgreSQL databases into a single file. This file contains several SQL commands that can be used as input to psql to restore the databases. The pg_dumpall reads tables from all databases, so you will have to connect to PostgreSQL as a superuser to produce a complete dump.

The basic syntax of the pgdump_all command is shown below:

pg_dumpall [option] > dump.sql

A brief explanation of each option is shown below:

• -h Specify database server host

• -p Specify database server port

• -c Clean databases before recreating

• -g Dump only global objects, no databases

• -r Dump only roles, no databases or tablespaces -s Dump only the schema, no data -S Specify superuser user name to use in the dump -t Dump only tablespaces definition.

To export all PostgreSQL databases, run the following command:

pg_dumpall > dump.sql

To back up objects in all databases, including roles, tablespaces, databases, schemas, tables, indexes, triggers, functions, constraints, views, ownerships, and privileges, you use the following command:

pg_dumpall -s > dump.sql

If you want to back up role definition only, use the following command:

pg_dumpall -r > dump.sql

If you want to back up the tablespaces definition, use the following command:

pg_dumpall -t > dump.sql

Import a PostgreSQL Database with pg_restore Command

The pg_restore is a command-line utility used to import or restore a PostgreSQL database from an archive created by pg_dump. Generally, it is used if you choose custom, directory, or tar format when creating a dump file.

The pg_restore command provides a -j option to specify the number of threads for restoration. This will allow you to perform parallel restores and dramatically speed up the process. Currently, the pg_restore support this option for the only custom file format.

The basic syntax of the pg_restore command is shown below:

pg_restore -c -U db_user -W -F t -d db_name dump_file.tar

A brief explanation of each option is shown below:

• -U Specify the user who is used for connecting to the PostgreSQL database server.

• -d Specify the database on which you want to import or restore a database.

• -W Used to prompt for a password before connecting to the PostgreSQL server.

• -F format Specify the format of the archive.

• -j Specify the number of parallel jobs to restore.

• -c Clean a database before restoring them.

• -C Create a new database before restoring it.

• -e Exit the process if an error has been encountered.

For example, to import a single database named testdb from the dump file named dump.tar, run the following command:

pg_restore -c -U username -W -F t -d testdb dump.tar

If you want to import all databases from the alldump.tar file, run the following command:

pg_restore -c -U username -W -F t alldump.tar

Import a PostgreSQL Database with psql Command

The psql is a command-line tool that allows you to import the SQL dump file generated by the pg_dump or pg_dumpall.

The basic syntax to import a single database using the psql tool is shown below:

psql -U user_name -W -d db_name -f dump.sql

The basic syntax to import all databases using the psql tool is shown below:

psql -U user_name -W -f dump.sql

To import a single database from the dump file named dump.sql into the database named testdb, run the following command:

psql -U username -W -d testdb -f dump.sql

If you want to stop importing a database in case of errors, you add the --set ON_ERROR_STOP=on option:

psql -U username -W -d testdb --set ON_ERROR_STOP=on -f dump.sql

To import all PostgreSQL databases from the dump file named alldb_dump.sql, run the following command:

psql -U username -W -f alldb_dump.sql

Conclusion

In this guide, we explained how to export a PostgreSQL database using the pg_dump and pg_dumpall utility. We also explained how to import a dump file using the pg_restore and psql utility. I hope this will help you to perform your day-to-day backup jobs.