pingcap / pingcap/tiflash

[MPP/Optimizer] make Optimizer smart enough to process complex quiries like multi-shuffle join.

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priority/P1
Dominant language
C++
Stars
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Forks
423
Avg merge
1d 15h
Merged PRs (30d)
24

Description

  1. recognize the multi joins with equivalent join keys. like a = b = c = d then the group by key is a
  2. choose shuffle key smartly. Shuffle keys can be the subset of join keys, but might result in data skew.

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the MPP/Optimizer handling for multi-join plans and review how equivalent join keys and shuffle keys are represented. Use the a=b=c=d multi-join case as an initial example, then investigate how subset shuffle keys affect data skew. Done means the optimizer can process multi-shuffle joins and choose shuffle keys according to the stated constraints.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
databases, distributed-systems
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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