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expression, session: handle CASE WHEN specially when folding constant during outerJoin Simplification #11105

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merged 22 commits into from
Jul 24, 2019
Merged

expression, session: handle CASE WHEN specially when folding constant during outerJoin Simplification #11105

merged 22 commits into from
Jul 24, 2019

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lovewin99
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What problem does this PR solve?

fix issue:#11102 Unexcepted result in SELECT ... CASE WHEN ... ELSE NULL...

What is changed and how it works?

Check List

Tests

  • Unit test

@lovewin99
fix issue:pingcap#11102
7b00dbb 
                                                            Unexcepted result in `SELECT ... CASE WHEN ... ELSE NULL...`
@lovewin99
fix issue:pingcap#11102
f933936 
                                                            Unexcepted result in `SELECT ... CASE WHEN ... ELSE NULL...`
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codecov bot commented Jul 6, 2019 •
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Codecov Report

Merging #11105 into master will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             master     #11105   +/-   ##
===========================================
  Coverage   81.4185%   81.4185%           
===========================================
  Files           424        424           
  Lines         90795      90795           
===========================================
  Hits          73924      73924           
  Misses        11571      11571           
  Partials       5300       5300

@shenli shenli added contribution This PR is from a community contributor. type/bugfix This PR fixes a bug. labels Jul 8, 2019
@XuHuaiyu XuHuaiyu changed the title expression: fix issue:#11102 Unexcepted result in SELECT ... CASE WHEN ... ELSE NULL... expression: fix unexcepted result in SELECT ... CASE WHEN ... ELSE NULL... Jul 8, 2019
@XuHuaiyu XuHuaiyu added sig/planner SIG: Planner and removed component/expression labels Jul 8, 2019
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XuHuaiyu commented Jul 8, 2019

/run-all-tests

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/run-all-tests

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/run-integration-common-test
/run-common-test
/run-unit-test

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/run-all-tests

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mahjonp commented Jul 8, 2019

/rebuild

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/run-all-tests

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XuHuaiyu commented Jul 8, 2019

A simpler sql to re-produce this issue:

tidb> select t1.id from kankan1 t1 left join kankan2 t2 on t1.id = t2.id where (case  when t1.name='b' then 'case2' when t1.name='a' then 'case1' else NULL end) = 'case1';
+------+
| id   |
+------+
|    2 |
+------+

The root cause for this bug is that:
(case when t1.name='b' then 'case2' when t1.name='a' then 'case1' else NULL end) = 'case1' is regarded as a null-reject condition since it returns false after constant folding. Then left outer join is simplified to inner join wrongly.

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XuHuaiyu commented Jul 8, 2019

I wonder that can we put case-when in specialFoldHandler instead of forbidding it.

@lovewin99
fix issue:pingcap#11102
760d28a 
                                                            Unexcepted result in `SELECT ... CASE WHEN ... ELSE NULL...`
@lovewin99
fix issue:pingcap#11102
c7300dc 
                                                            Unexcepted result in `SELECT ... CASE WHEN ... ELSE NULL...`
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lovewin99 commented Jul 9, 2019 •
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I wonder that can we put case-when in specialFoldHandler instead of forbidding it.

@XuHuaiyu Good advice, I have modified it.

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/rebuild

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/rebuild

winkyao
winkyao reviewed Jul 10, 2019
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expression/constant_fold.go Outdated
isDeferredConst = isDeferredConst || isDeferred1
}

if l%2 == 1 && isFirstCondition {
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Does this mean the else expr? Please add some comments.

@lovewin99
fix issue:pingcap#11102
33565a0 
                                                            Unexcepted result in `SELECT ... CASE WHEN ... ELSE NULL...`
winkyao
winkyao reviewed Jul 12, 2019
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LGTM

@zz-jason zz-jason added the status/LGT2 Indicates that a PR has LGTM 2. label Jul 24, 2019
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/run-all-tests

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/run-all-tests

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/run-sqllogic-test-1

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/run-sqllogic-test-1

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/run-all-tests

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Repaired test. PTAL @zz-jason @XuHuaiyu

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zz-jason approved these changes Jul 24, 2019
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LGTM

@zz-jason zz-jason added status/can-merge Indicates a PR has been approved by a committer. status/all tests passed and removed status/LGT2 Indicates that a PR has LGTM 2. labels Jul 24, 2019
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sre-bot commented Jul 24, 2019

/run-all-tests

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sre-bot commented Jul 24, 2019

success

@sre-bot sre-bot merged commit c95d42a into pingcap:master Jul 24, 2019
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sre-bot commented Jul 24, 2019

cherry pick to release-2.1 failed

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sre-bot commented Jul 24, 2019

cherry pick to release-3.0 failed

lovewin99 added a commit to lovewin99/tidb that referenced this pull request Jul 25, 2019
@lovewin99
expression, session: handle CASE WHEN specially when folding consta…
876f1db 
…nt during outerJoin Simplification (pingcap#11105)

Test pass, auto merge by Bot
@lovewin99 lovewin99 mentioned this pull request Jul 25, 2019
Merged
lovewin99 added a commit to lovewin99/tidb that referenced this pull request Jul 25, 2019
@lovewin99
expression, session: handle CASE WHEN specially when folding consta…
37ef7f9 
…nt during outerJoin Simplification (pingcap#11105)

Test pass, auto merge by Bot
@lovewin99 lovewin99 mentioned this pull request Jul 25, 2019
Merged
sre-bot pushed a commit that referenced this pull request Jul 26, 2019
@lovewin99 @sre-bot
expression, session: handle CASE WHEN specially when folding consta…
64b4ffc 
…nt during outerJoin Simplification (#11105) (#11438)

All tests passed, auto merged by Bot
@lovewin99 lovewin99 deleted the master-3.0-issue branch July 30, 2019 06:37
This was referenced Aug 3, 2019
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@zz-jason zz-jason zz-jason approved these changes

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@lovewin99 @XuHuaiyu @mahjonp @zimulala @zz-jason @sre-bot @winkyao @shenli