Introduction to PostgreSQL Incremental backup
PostgreSQL provides the incremental backup functionality to the user, in which that PostgreSQL server saves all user modified data or we can say different transactions such as update, insert and delete and at the same time it performs the write operation into a WAL log file. The WAL means to write ahead a log file that is used to store the whole history of the database. Incremental database backup is also called point in time recovery, online backup, or archive backup. We can backup all data within zero down time by using an incremental backup process and it is also helpful to save the storage space of memory.
Syntax:
pg_start_backup()
Explanation
There are different ways to take the backup of the database. In the above syntax, we use a simple command or we can say function that is start_backup (). By using this command we easily create the backup of the database and log into the log file by using a label.
select pg_start_backup();
Explanation
This is another way to back up the database, here we use the select statement with start_backup() command to backup the database as shown in the above syntax. The above-mentioned first syntax is optional as per our requirement we can use any method to backup the database into the log file.
How to Perform Incremental backup in PostgreSQL?
Now let’s see how we can perform the incremental backup in PostgreSQL as follows. First, let’s see what the WAL file is as follows.
WAL represents Write Ahead Log. WALs are utilized in virtually all cutting edges of the RDBMS frameworks to give atomic operation or durable transactions. Changes to the information contained in a PostgreSQL data set group overseen by a solitary PostgreSQL Server perform all the process only by using the transactions. The alterations made to the information by operation are recorded as an arranged grouping of WAL files. These records are composed into fixed-length documents called WAL segment files, or basically WAL documents. WAL records live in $PGDATA/pg_wal, where $PGDATA is the information catalog for the data set group.
WAL documents are produced steadily, in grouping, beginning from cluster creation. They continue to get produced however long adjustments happen to the cluster. The WAL document mechanism is crucial for the working of PostgreSQL, and can’t be killed.
After the progressions are first set up as WAL accounts, they must be applied to the on-plate portrayal of the actual information. This cycle is called checkpointing and occurs behind the scenes naturally (it can likewise be constrained physically). The point until which checkpointing was done is known as the REDO point. Checkpointing is likewise a fundamental piece of Postgres engineering and can’t be killed.
WAL File Retention:
Basically, WAL file retention is a very important part of the PostgreSQL database because in some cases we need to perform the crash recovery at that time PostgreSQL server restart and apply some modification from the WAL file. After the transaction, it gives us assurance all data from the database is in its consistent state with the last completed transaction. We have another way that replication, with help of replication we can back up all the records from the database. To perform replication operations we required standby servers. For example, we have as 50 records into the WAL file and standby backup first 30 WAL records and most recently 20 WAL records we also required so at that time we can again apply the standby server and it receives the next 20 from 31 onwards.
Now let’s see how we can archival WAL file as follows:
In the PostgreSQL server, WAL file records each and every replica of transactions. So PostgreSQL provides the functionality to archive the WAL file after a transaction.
Now let’s see incremental backup or Point in Time Recovery:
PITR provides the functionality to backup and restores the database; we can fetch the records from the database up to a specified timestamp. For that operation, we need to create the file that we call as recovery.cnf file, in this file we can store the target timestamp of records. As per requirement, we can fetch the records by using the restore_command that is specified by PostgreSQL.
At the point when a PostgreSQL server measure fires up and finds recovery.conf document in the information registry, it startup in an uncommon mode called “recovery mode”. When the client connections are denied in recovery mode, Postgres gets WAL documents and applies them until the recovery target (for this situation, switches around to the predefined timestamp) is accomplished. At the point when the objective is accomplished, the server as a matter of course stops WAL replay (different activities are conceivable). Now, you should analyze the condition of the reestablishment and if everything looks alright, start to leave recovery mode and proceed with the ordinary activity.
Examples
Now let’s see different examples of incremental backup in PostgreSQL as follows. Now let’s see the process to perform the incremental backup as follows.
First, we need to create the new table name as sample_incre from another two tables as follows.
select * from pg_class;
When we execute the above statement it shows the records from pg_class table and it contains the 427 records. As shown in the screenshot below:
After that PostgreSQL creates the log file as shown in the below screenshot as follows.
Now take full backup by using the following statement as follows.
SELECT pg_start_backup('sample_incremental', false, false);
Explanation
In the above statement, we use pg_start_backup command to take the full-back of the database. Here we can use a label that means any string that uniquely identifies the backup. The final output of the above statement we illustrated by using the following screenshot as follows.
After backup, we need to stop the backup process by using the following command.
SELECT * FROM pg_stop_backup(false);
Explanation
After execution of the above statement, it stops the backup process as shown in below screenshot as follows.
Conclusion
We hope from this article you learn Incremental backup in PostgreSQL. From the above article, we have learned the basic syntax of Incremental backup and we also see different examples of Incremental backup. From this article, we learned how and when we use the Incremental backup in PostgreSQL.
Recommended Articles
This is a guide to PostgreSQL Incremental Backup. Here we discuss the definition, syntax, How to perform Incremental backup in PostgreSQL? examples with code implementation. You may also have a look at the following articles to learn more –
