Optimize the disk read ops of the delta layer
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- Dominant language
- C++
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Description
PSMReadIOCalls: The number of read system call from the delta layer.
PSMReadPages: The number of pages read from PageStorage.
https://github.com/pingcap/tics/blob/c1a762215bbfbaddccc8f4800fbd30265cfabd8b/dbms/src/Storages/Page/PageUtil.cpp#L153
https://github.com/pingcap/tics/blob/c1a762215bbfbaddccc8f4800fbd30265cfabd8b/dbms/src/Storages/Page/PageFile.cpp#L816
We can see that the number of PSMReadIOCalls is about 7~10 times of PSMReadPages. This is mostly because the SQL usually queries multiple columns, and we can not merge the read for different columns in the delta packs.
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reading the referenced sections of dbms/src/Storages/Page/PageUtil.cpp and dbms/src/Storages/Page/PageFile.cpp, then trace how delta-pack reads are issued for queries touching multiple columns. Done means reducing the gap between PSMReadIOCalls and PSMReadPages for those reads, while validating the result against the reported workload metrics.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- databases, performance
- Issue type
- Refactor
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100