pg_dump compression specifications in PostgreSQL 16

12.2022 / Category: , / Tags: | |

What is pg_dump compression?

pg_dump is a PostgreSQL utility for backing up a local or remote PostgreSQL database. It creates a logical backup file that contains either plain SQL commands for recreating the database, or a binary file that can be restored with the pg_restore utility. The binary backup file can be used to restore the database from scratch, or to restore only selected parts of the database.

Binary files produced by pg_dump can be compressed to reduce their size. This is done by passing the -Fc or --format=custom flag to pg_dump, which causes it to produce a compressed backup file. The file can then be decompressed with pg_restore later. To indicate the level of compression, you should provide option -Z, followed by a number which indicates the compression level (0-9, where 0 is no compression and 9 is the maximum compression level.) The compression algorithm used in pg_dump is the same as used in gzip.

What is new for pg_dump compression in PostgreSQL 16?

Georgios Kokolatos implemented a patch which allows you to specify not only the level of compression to be used but also a method for compression.

The patch was reviewed and committed by Michael Paquier. The commit message is:

As you can see, only two method specifiers are implemented here: none and gzip. But the importance of this change is that it prepares the infrastructure for adding all other compression methods available at the time, like gzip, lz4, zstd.

Let's try it out!

The results show that the non-zero compression level raises an error when the compression algorithm is none. The results also show that a compression level other than zero is required when the compression algorithm is gzip.


pg_dump's -Z/--compress in PostgreSQL 16 will support more than just an integer. It can be used to specify the method and level of compression used. The default is still gzip with a level of 6. As I already said, pg_dump is sometimes used to update and/or upgrade the database. In case you want to understand the difference between an update and an upgrade, check out this blog post by Hans-Jürgen Schönig. Or check our other related publications about updating and upgrading.

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