What are the compression options for storing large amounts of text in Postgres?

Question

I need to store large amounts of text in Postgres, mainly command logs and the output of long running commands and need to know if there are some settings that could help compress the data transparently with a tool like zlib, or some other native space saving methods.

The data is primarily read only data, so writing is not a problem.

• user1822: from the manual: "Long strings are compressed by the system automatically" and here is a more detailed description: postgresql.org/docs/current/static/storage-toast.html
• Craig Ringer: We use quite a low ratio compression algorithm though, because it must have a low CPU cost. So it can still be worth doing another form of compresion and setting EXTERNAL storage on the column.
• vfclists: @CraigRinger When you say another form of compression do you mean setting some additional Postgres options, or compiling some additional module, whether a ready made library or one of your own?

Answer 1

By default Postgres automatically compresses everything TEXT. It uses a simple lzcompress algorythm:

https://www.postgresql.org/docs/9.3/storage-toast.html

There is a plugin that will probably evolve to LZ4 compression support for TEXT:

https://github.com/zilder/pg_lz4

There is a FDW that also support compression:

https://www.citusdata.com/blog/2014/04/03/columnar-store-for-analytics/

Answer 2

If you are doing this for logs, then TimescaleDB compression is a good option. This is because there is a strong time-based component in logs and command output and thus we consider this time-series data and can use time-based techniques to compress this data.

Disclosure: I work for Timescale and helped develop this feature.

• mustaccio: So, how exactly the TimescaleDB columnar compression helps with large text values? Your link says explicitly that's exactly what TOAST compression is for.
• kworr: Also want to see a better answer as a fan of TimescaleDB to get a better understanding how text data can be managed in a more efficient way.