Example Codes for Restoring PostgreSQL Databases

This message arises when you attempt to use the pg_restore command to restore a database backup file that's in plain text format. pg_restore is designed to handle archive-format backups, which are compressed and optimized for efficient restoration.

Why Text Format Needs psql:

• psql: This is the interactive PostgreSQL command-line tool. It allows you to execute SQL statements directly against the database server.
• Text Format: When you create a database backup using pg_dump by default (without the -F or --format option), it generates a plain text file containing all the SQL commands necessary to recreate the database schema and data.

Restoring a Text Format Dump:

To restore a text format dump, you need to use psql to feed these SQL statements line by line into the PostgreSQL server:

psql -h <host> -U <username> -d <database_name> < backup_file.sql

• Replace <host> with the hostname or IP address of your PostgreSQL server (usually localhost if running locally).
• Replace <username> with your PostgreSQL username with appropriate permissions.
• Replace <database_name> with the name of the database you want to restore.
• Replace <backup_file.sql> with the actual path to your text format dump file.

Alternative: Creating Archive Format Backups:

If you want to use pg_restore for faster and more robust restorations, you can create archive format backups using pg_dump with the -Fc or --format=custom option:

pg_dump -h <host> -U <username> -d <database_name> -Fc > backup.tar

Then, to restore from the archive format backup:

pg_restore -h <host> -U <username> -d <database_name> backup.tar

Choosing the Right Method:

• Use psql for restoring simple text format backups.
• Use pg_dump with -Fc and pg_restore for archive format backups that offer better performance and features like incremental backups.

Example Codes for Restoring PostgreSQL Databases

Restoring from Text Format Dump using psql:

# Assuming your text format dump is named "mydatabase.sql" and you want to restore it to a database named "mydatabase_restored":

psql -h localhost -U postgres -d mydatabase_restored < mydatabase.sql

Explanation:

• psql: Invokes the PostgreSQL command-line tool.
• -h localhost: Specifies the hostname of the PostgreSQL server (replace with your actual hostname if needed).
• -U postgres: Connects as the user "postgres" (change username if different).
• -d mydatabase_restored: Connects to the target database "mydatabase_restored".
• < mydatabase.sql: Redirects the input from the "mydatabase.sql" file, feeding its contents (SQL statements) to the database.

Restoring from Archive Format Backup using pg_dump and pg_restore:

a) Creating the Archive Format Backup:

# Assuming your database is named "mydatabase":

pg_dump -h localhost -U postgres -d mydatabase -Fc > mydatabase_backup.tar

• pg_dump: Invokes the PostgreSQL dump utility.
• -d mydatabase: Specifies the database to back up.
• -Fc: Creates an archive format backup (compressed and optimized).
• > mydatabase_backup.tar: Redirects the output to a file named "mydatabase_backup.tar".

b) Restoring the Database from the Archive Format Backup:

# Assuming you want to restore the backup into a new database named "mydatabase_restored":

pg_restore -h localhost -U postgres -d mydatabase_restored mydatabase_backup.tar

• -d mydatabase_restored: Specifies the target database for restoration.
• mydatabase_backup.tar: Specifies the archive format backup file.

• This advanced feature allows you to restore your database to a specific point in time, even if you don't have a full backup. However, it requires setting up continuous archiving (WAL archiving) beforehand. You can then use the pg_archivecleanup and pg_basebackup commands to create a consistent recovery point and restore your database to that point.

Third-Party Backup and Recovery Tools:

• Several third-party tools offer backup and recovery functionalities for PostgreSQL. These tools often provide additional features like scheduling, automated backups, and user-friendly interfaces. Some popular options include:
  • pgAdmin: A web-based administration tool with backup and restore capabilities.
  • Barman: A command-line tool for automated PostgreSQL backups and recovery.
  • Patroni: A high availability solution for PostgreSQL that includes features like automated failover and backups.

Logical Replication:

• This technique allows you to replicate data changes from one PostgreSQL server (source) to another (replica) in real-time. If your primary database encounters an issue, you can quickly failover to the replica for minimal downtime. While not strictly a restoration method, it provides a continuous copy of your database for disaster recovery.

• For basic restores from text format backups, psql is a simple and effective solution.
• For archive format backups with better performance, use pg_restore.
• If you need point-in-time recovery or advanced backup management features, consider PITR or third-party tools.
• Logical replication offers a different approach for disaster recovery by maintaining a real-time copy of your database.