Describe the process of implementing advanced backup and recovery strategies in PostgreSQL, such as incremental backups, parallel backups, and synthetic backups.?

Implementing advanced backup and recovery strategies in PostgreSQL involves taking advantage of several features available within the database system. The following are some of the advanced backup and recovery strategies that can be implemented in PostgreSQL:

1. Incremental Backups: PostgreSQL supports incremental backups that help reduce the backup time and the amount of data that needs to be backed up. In incremental backups, only the changes made since the last backup are backed up, rather than the entire database. This is achieved by setting a flag called ‘–xid‘ in the ‘pg_basebackup‘ command. It only copies WAL files that contain changes made since the last backup. A sample code block to perform an incremental backup using ‘pg_basebackup‘ is given below:

pg_basebackup --checkpoint=fast --xlog --incremental --pgdata=/path/to/datadir --label=INCREMENTAL-BACKUP-1 /path/to/backupdir

2. Parallel Backups: PostgreSQL provides the ability to perform parallel backups to take advantage of multi-core CPUs. This feature helps to reduce the backup time and speed up the recovery time in case of a disaster. Parallel backups can be performed using the pg_dump utility, which divides the backup into multiple parts that can be run simultaneously. Code snippet to illustrate performing parallel backups using pg_dump is shown below:

pg_dump -Fd -j 4 -f /path/to/backupdir dbname

Here, ‘-j‘ option specifies the number of parallel processes, and ‘-Fd‘ specifies the output format.

3. Synthetic Backups: A synthetic backup is a full backup that is created by merging an initial full backup with subsequent incremental backups. Synthetic backups help reduce the recovery time by providing a single backup that contains all the changes since the last full backup. Synthetic backups can be created using tools like pgBackRest and Barman. An example code snippet to illustrate performing synthetic backups using pgBackRest is shown below:

pgbackrest --stanza=db backup --type=synthetic

The above command creates a synthetic backup of the ‘db‘ cluster using pgBackRest.

In summary, implementing advanced backup and recovery strategies in PostgreSQL requires taking advantage of features such as incremental backups, parallel backups, and synthetic backups. The use of the appropriate backup strategy depends on the backup size, business needs and the database environment infrastructure.