Return non-Nullable results from COUNT(DISTINCT)#11593
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alexey-milovidov merged 3 commits intomasterfrom Jun 14, 2020
Merged
Return non-Nullable results from COUNT(DISTINCT)#11593alexey-milovidov merged 3 commits intomasterfrom
alexey-milovidov merged 3 commits intomasterfrom
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This was referenced Oct 14, 2020
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This was referenced Nov 20, 2020
azat
reviewed
May 17, 2023
| else | ||
| return std::make_shared<AggregateFunctionNullUnary<false>>(nested_function, arguments, params); | ||
| { | ||
| if (serialize_flag) |
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Interesting that nobody noticed that this breaks the backward compatibility, seems nobody uses aggregate functions over Nullable (it is questionable, but still):
$ docker run yandex/clickhouse-server:20.4 clickhouse local -q "select maxState(toNullable(1))" | xxd
00000000: 0101 0a ...
$ docker run yandex/clickhouse-server:20.5 clickhouse local -q "select maxState(toNullable(1))" | xxd
00000000: 0101 010a ....
azat
reviewed
May 17, 2023
| return adapter; | ||
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| bool return_type_is_nullable = !nested_function->returnDefaultWhenOnlyNull() && nested_function->getReturnType()->canBeInsideNullable(); | ||
| bool serialize_flag = return_type_is_nullable || nested_function->returnDefaultWhenOnlyNull(); |
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By the way, @alexey-milovidov why the NULL flag is written if returnDefaultWhenOnlyNull == true?
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It was probably left for backward compatibility.
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Superseded by #11661
Return non-Nullable result from COUNT(DISTINCT), and
uniqaggregate functions family. If all passed values are NULL, return zero instead. This improves SQL compatibility.Detailed description / Documentation draft:
If all arguments are NULL literals, we still return NULL.