PostgreSQL version 8.1 introduced some performance features which include partitioned tables performance, improvement in GiST, R-tree and some improvement in optimizer. This section describes only the performance features. For a full list of features introduced in version 8.1, look at the release notes of PostgreSQL:
https://www.postgresql.org/docs/8.1/static/release-8-1.html
- The shared buffer cache used to hold database data was redesigned for better concurrent use. This change is the major reason 8.1 is the earliest PostgreSQL version with good scalability.
- Bitmap scans allow combining multiple single-column indexes for queries that reference more than one column. This decreases the need to create computationally expensive multi-column indexes on tables.
- Autovacuum, formerly a module that had to be explicitly loaded, was integrated into the main server (but not started by default).
- Table partitioning is improved to allow skipping partitions that can't possibly satisfy a query.
- Indexes are automatically used for MIN() and MAX() queries.