Fix if, multiIf's nullable bug. by janplus · Pull Request #5238 · ClickHouse/ClickHouse · GitHub
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Fix if, multiIf's nullable bug.#5238

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alexey-milovidov merged 1 commit into
ClickHouse:masterfrom
janplus:if-nullable-bug
May 12, 2019
Merged

Fix if, multiIf's nullable bug.#5238
alexey-milovidov merged 1 commit into
ClickHouse:masterfrom
janplus:if-nullable-bug

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@janplus

@janplus janplus commented May 10, 2019

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I hereby agree to the terms of the CLA available at: https://yandex.ru/legal/cla/?lang=en

For changelog. Remove if this is non-significant change.

Category (leave one):

  • Improvement
  • Backward Incompatible Change

Short description (up to few sentences):
The if, multiIf functions should not rely on the condition's Nullable, but should only rely on the branches.

You may check the MySQL & Postgresql's results here:
http://sqlfiddle.com/#!9/25e4d/4
http://sqlfiddle.com/#!17/486b3/3

@alexey-milovidov alexey-milovidov added can be tested pr-improvement Pull request with some product improvements sql-compatibility labels May 11, 2019
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@alexey-milovidov alexey-milovidov merged commit 9ce2dd8 into ClickHouse:master May 12, 2019
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Although it doesn't seem logical for me.

@janplus

janplus commented May 12, 2019

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Hmm, the data analyst in my company reported this bug to me. I also double checked this logic, and found that MySQL, Postgresql, IBM DB2 all leverage the same logic, so I decide to behave the same way.

@janplus janplus deleted the if-nullable-bug branch May 12, 2019 14:02
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