Here is the list of all performance features but you can always get the complete listing from here: https://www.postgresql.org/docs/9.3/static/release-9-3.html
- A new option FREEZE added in COPY command to avoid later overhead of marking tuple frozen
- Improvement of session waiting for commit_delay
- Improve VACUUM to recheck the visibility, to enhance the chance that page beaning mark all visible
- Add a cache called per-resource-owner useful for pg_dump
- Add SP-GiST (https://www.postgresql.org/docs/9.3/static/rangetypes.html#RANGETYPES-INDEXING) support for range data types
- Allow GiST indexes to be unlogged, and improve the performance of GiST index
- Improve concurrency of hash index operations
- Improve optimizer's cost estimation for index access
- Avoid scanning the entire relation cache at commit of a transaction that creates a new relation
- Suppress no-op Result and Limit plan nodes
- Reduce optimizer overhead by not keeping plans on the basis of cheap startup cost when the optimizer only cares about total cost overall