[potenial bug] TiFlash's join output schema is different than TiDB's.
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- Dominant language
- C++
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Description
Tiflash join's output schema is strictly equal to input schema's union.
so planner must reset mppjoin schema in physicalOptimize.
it may broke the optimization or assumption done by logicalOptimize.
for example:
https://github.com/pingcap/tidb/issues/34765
Contributor guide
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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 locating physicalOptimize and logicalOptimize, then trace how the mppjoin schema is produced and consumed for TiFlash joins. Compare the output-schema behavior with TiDB using issue #34765 as context; the work is done when the planner's schema handling matches the expected TiDB behavior without breaking logical-optimization assumptions.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- backend, databases
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100