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planner: the UNION's merge type should exclude the pure NULL #26561

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merged 2 commits into from
Jul 26, 2021

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@winoros winoros commented Jul 26, 2021

What problem does this PR solve?

Issue Number: close #26559

Problem Summary:

When there are pure NULL values in the child query, TiDB would get the wrong length of some field types, causing the wrong return results.

What is changed and how it works?

Proposal: xxx

What's Changed:

When merging the field types of the children, we ignore the pure NULLs.

Check List

Tests

  • Unit test

Release note

  • Fix the case that TiDB would return the wrong result when the children of the UNION contain pure NULL values

@ti-chi-bot ti-chi-bot added the size/S Denotes a PR that changes 10-29 lines, ignoring generated files. label Jul 26, 2021
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LGTM

@ti-chi-bot ti-chi-bot added the status/LGT1 Indicates that a PR has LGTM 1. label Jul 26, 2021
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[REVIEW NOTIFICATION]

This pull request has been approved by:

  • XuHuaiyu
  • qw4990

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

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@ti-chi-bot ti-chi-bot added status/LGT2 Indicates that a PR has LGTM 2. and removed status/LGT1 Indicates that a PR has LGTM 1. labels Jul 26, 2021
@ichn-hu ichn-hu mentioned this pull request Jul 26, 2021
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winoros commented Jul 26, 2021

/merge

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This pull request has been accepted and is ready to merge.

Commit hash: 4d899d8

@ti-chi-bot ti-chi-bot added the status/can-merge Indicates a PR has been approved by a committer. label Jul 26, 2021
@ti-chi-bot ti-chi-bot merged commit 71638ee into pingcap:master Jul 26, 2021
ti-srebot pushed a commit to ti-srebot/tidb that referenced this pull request Jul 26, 2021
Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
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cherry pick to release-4.0 in PR #26570

ti-srebot pushed a commit to ti-srebot/tidb that referenced this pull request Jul 26, 2021
Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
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cherry pick to release-5.0 in PR #26571

ti-srebot pushed a commit to ti-srebot/tidb that referenced this pull request Jul 26, 2021
Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
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cherry pick to release-5.1 in PR #26572

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needs-cherry-pick-release-5.0 needs-cherry-pick-release-5.1 sig/planner SIG: Planner size/S Denotes a PR that changes 10-29 lines, ignoring generated files. status/can-merge Indicates a PR has been approved by a committer. status/LGT2 Indicates that a PR has LGTM 2. type/bugfix This PR fixes a bug.
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Uncorrect result when there's union
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