Improve the hash join performance by replacing the RawTable to a hash table that supports prefetching
- Dominant language
- Rust
- Stars
- 9.3k
- Forks
- 2.4k
- Avg merge
- 3d 7h
- Merged PRs (30d)
- 344
Description
### Is your feature request related to a problem or challenge?
When testing the TPCH q17 on my PC, based on #6800, it costs around 2.4s. Among them, it costs around 800ms for constructing the `RawTable` of `JoinHashMap`.
To only find the hash location, the structure, `RawTable`, we used is too complex and the overhead is too heavy.
### Describe the solution you'd like
We can simple use a fixed size of vector with a hash mask to look up the hash location.
After applying the replacement, it only cost less than 100ms for the construction of `JoinHashMap`. And the overall time cost for the q17 is reduced from 2.4s to 1.8s.
### Describe alternatives you've considered
_No response_
### Additional context
_No response_
Contributor guide
Research direction
Start by tracing JoinHashMap construction and its RawTable usage, using the TPCH q17 case and issue #6800 as context. Compare the current hash-location lookup with the proposed fixed-size vector and hash mask approach. Done means the replacement supports prefetching and improves JoinHashMap construction and overall q17 timings as described.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- databases, performance
- Issue type
- Feature
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Active
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100