zheap
zheap is an alternative storage engine proposed by EnterpriseDB intended - in combination with pluggable storage - to minimize the need for tuple vacuuming inherent in PostgreSQL's native MVCC implementation.
zheap was originally proposed in March 2013 in this thread on pgsql-hackers.
Design
The design of zheap is centred around the concept of UNDO logs, by which redundant tuples are written to storage outside of the main heap, and can easily be removed when no longer required. This also means the main heap is no longer prone to bloat caused by the presence of dead tuples, and vacuuming becomes much less of an issue.
Development status
Development was initially undertaken by EnterpriseDB, but the associated GitHub repository was last updated in 2019.
As of 2020, development is being continued out by CyberTec with funding by Heroic Labs (source).
Useful links
- PostgreSQL zheap: Current status - July 2021 blog article by CyberTec
- zheap: Inspecting storage sizes - October 2020 blog article by CyberTec
- zheap: Reinvented PostgreSQL storage - October 2020 blog article by CyberTec
- Zheap: A Storage Engine to Provide Better Control Over Bloat - March 2018 blog article by EnterpriseDB