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@AtulKsol
Last active September 15, 2024 12:29
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Commands to backup & restore database
  1. pg_dump is a nifty utility designed to output a series of SQL statements that describes the schema and data of your database. You can control what goes into your backup by using additional flags.
    Backup: pg_dump -h localhost -p 5432 -U postgres -d mydb > backup.sql

    Restore: psql -h localhost -p 5432 -U postgres -d mydb < backup.sql

    -h is for host.
    -p is for port.
    -U is for username.
    -d is for database.

  2. Single transaction restore:
    you can use –single-transaction in your restore command. It wraps out entire restore operation in one transaction, if something goes wrong it rollbacks all the changes.
    psql –single-transaction -h localhost -p 5432 -U postgres -d mydb < backup.sql

  3. Compressed Backup:
    If your backup is too big, you can use any compression utility to compress it. I prefer gzip.
    Backup: pg_dump -h localhost -p 5432 -U postgres -d mydb | gzip > backup.gz

    Restore: gunzip -c backup.gz | psql -h localhost -p 5432 -U postgres -d mydb

  4. Split Backup file:
    If you are going to email your backup files or transfer them via any medium on internet I will suggest splitting the files into short files. You can use split utility for splitting the files with a size limit. In the example I am usinf 2mb size limit.
    Backup: pg_dump -h localhost -p 5432 -U postgres -d mydb | split -b 2m – backup.sql

    Restore: cat backup.sql* | psql -h localhost -p 5432 -U postgres -d mydb

  5. Split compressed Backup file:
    This is just a combination of point 3 and 4. We first compress the file then split it instead of splitting the plain file.
    Backup: pg_dump -h localhost -p 5432 -U postgres -d mydb | gzip | split -b 1m – backup.gz

    Restore: cat backup.gz* | gunzip | psql -h localhost -p 5432 -U postgres -d mydb

  6. Parallel Backup:
    You can allow pg_dump to dump the backup data in parallel by including the -j flag. It tells pg_dump the number of tables it can dump in parallel. Parallel backup only works when you use more than one files for writing backup data hence directory. -F d sets the format to directory and -f provides the directory name.
    Backup: pg_dump -F d -f backup -j 20 -h localhost -p 5432 -U postgres -d mydb

    Restore: pg_restore -F d -j 20 -h localhost -p 5432 -U postgres -d mydb backup

  7. Backup of a specific table:
    You can take backup of a specify table by adding -t flag.
    Backup: pg_dump -h localhost -p 5432 -U postgres -d mydb -t my_table > backup.sql

    Restore: psql -h localhost -p 5432 -U postgres -d mydb < backup.sql

  8. Take Backup of all databases:
    pg_dumpall is used to take backup of all of your postgresql database. I think it is just a wrapper around pg_dump. It will ask password for every database.
    Backup: pg_dumpall -h localhost -p 5432 -U postgres > backup.sql

    Restore: psql -h localhost -p 5432 -U postgres < backup.sql

  9. Custom format backup (-F c):
    Keith mentioned in the comment that -F c provides better options at the time of restoring the backup. You can take the backup of whole database and restore only selected tables by using -t flag. It also compresses the backup data for you.All these feature are also provided by the directory format (-F d) too. The main difference between directory and custom format is that custom format generates a single file and directory format generates a directory full of files. A Single file(single stream) gives us many advantages like outputting the backup data over SSH or transferring it to some other service is easy compared to a directory(multiple stream)

    One more difference is that you can not use parallel backup option (-j) with custom format backup. It is obvious since it uses only one stream.

    So how do you take backup using custom format and restore it.

    Backup: pg_dump -F c -h localhost -p 5432 -U postgres -d mydb > backup.dat

    Restore: pg_restore -F c -h localhost -p 5432 -U postgres -t my_table -d mydb backup.dat

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