PostgreSQL pg_restore
PostgreSQL's `pg_restore` is a utility for restoring a PostgreSQL database from an archive created by `pg_dump`. It is used to reconstruct the database to its original state from a backup file.
Usage
The `pg_restore` tool is employed when you need to restore data from a backup file into a PostgreSQL database. It supports various archive formats (e.g., custom, directory, tar) and options to control what is restored.
bash
pg_restore [options] backup_file
In this syntax, `backup_file` specifies the archive file to restore from, and `[options]` includes various flags to fine-tune the restoration process.
Examples
1. Basic Restore
bash
pg_restore -d mydatabase mybackup.dump
This restores the entire content of `mybackup.dump` into the `mydatabase` database.
2. Restore with Specific Schema
bash
pg_restore -d mydatabase --schema=public mybackup.dump
This command restores only the `public` schema from `mybackup.dump` into `mydatabase`, allowing for selective restoration.
3. Restore with Parallel Jobs
bash
pg_restore -d mydatabase -j 4 mybackup.dump
Here, the `-j 4` option enables parallel processing with four jobs, which speeds up the restoration of large databases.
4. Restore with Specific Table
bash
pg_restore -d mydatabase --table=mytable mybackup.dump
This command restores only the `mytable` table from `mybackup.dump` into `mydatabase`.
5. Data-Only Restore
bash
pg_restore -d mydatabase --data-only mybackup.dump
This option restores only the data, without creating any database schema objects.
6. Schema-Only Restore
bash
pg_restore -d mydatabase --schema-only mybackup.dump
This option restores only the schema objects, excluding the data.
Tips and Best Practices
- Use the correct format. Ensure that the archive format of the backup file matches the capabilities of `pg_restore`.
- Test restores regularly. Perform test restores to verify that your backups are valid and can be restored as expected.
- Leverage parallel jobs. Use the `-j` option to speed up restoration, especially for large databases.
- Selective restoration. Use options like `--table`, `--schema`, `--data-only`, or `--schema-only` to restore specific parts of the database when full restoration isn't necessary.
- Check dependencies. Be aware of object dependencies when restoring specific tables or schemas to avoid missing references. Consider using the `--disable-triggers` option to manage dependencies effectively during data-only restores.
- Error Handling. Common errors during restoration include missing tablespaces or roles. Ensure that the target database environment matches the original setup. Use log files to diagnose and troubleshoot errors.