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Make the content in HistColl.ColID2IdxIDs stable #38457

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time-and-fate opened this issue Oct 13, 2022 · 0 comments · Fixed by #38458
Closed

Make the content in HistColl.ColID2IdxIDs stable #38457

time-and-fate opened this issue Oct 13, 2022 · 0 comments · Fixed by #38458
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sig/planner SIG: Planner type/enhancement The issue or PR belongs to an enhancement.

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Enhancement

As you can see in the logic of GenerateHistCollFromColumnInfo(), the content of HistColl.ColID2IdxIDs comes from the result of iterating through a map. However, in Go, we can't assure the order of iterating a map. This adds an unstable factor in the row count estimation logic.
We need to make it stable.
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sig/planner SIG: Planner type/enhancement The issue or PR belongs to an enhancement.
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statistics, planner: make the content in HistColl.ColID2IdxIDs stable time-and-fate/tidb
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