[BUG](exec) fix coalesce function output null (#63092)#63996
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Issue Number: close #xxx
Example: COALESCE(same_department_income_amount, 0) ==> outputs NULL
(where same_department_income_amount is of type double).
When assigning the value to the result column in the computation, the
assignment is done unconditionally (forced), as in:
```cpp
result_raw_data[row] +=
column_raw_data[row] *
typename ColumnType::value_type(!(null_map_data[row] | filled_flag[row]));
```
If the argument column column_raw_data's null_map[row] is 1, then the
value stored in column_raw_data[row] is garbage data. This garbage may
contain values such as NaN. If a preceding argument of COALESCE happens
to be assigned NaN, then during subsequent assignments we run into cases
like:
0 * NaN = NaN
num + NaN = NaN
so the assigned result also becomes NaN, which causes value pollution.
By rights the final output should also be NaN, but what is actually
returned is NULL. The reason is that during result serialization/output,
NaN values are emitted as NULL.
```cpp
tatus DataTypeNumberSerDe<T>::_write_column_to_mysql(const IColumn& column,
MysqlRowBuffer<is_binary_format>& result,
int row_idx, bool col_const,
const FormatOptions& options) const {
//...
else if constexpr (std::is_same_v<T, float>) {
if (std::isnan(data[col_index])) {
// Handle NaN for float, we should push null value
buf_ret = result.push_null();
} else {
buf_ret = result.push_float(data[col_index]);
}
}
//...
}
```
Contributor
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Thank you for your contribution to Apache Doris. Please clearly describe your PR:
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Contributor
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run buildall |
added 2 commits
June 3, 2026 11:43
Contributor
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run buildall |
yiguolei
approved these changes
Jun 4, 2026
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What problem does this PR solve?
Cherry-picked from #63092
Issue Number: close #xxx
Related PR: #xxx
Problem Summary:
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Test
Behavior changed:
Does this need documentation?
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