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Posted to github@arrow.apache.org by "mustafasrepo (via GitHub)" <gi...@apache.org> on 2023/05/31 10:32:56 UTC
[GitHub] [arrow-datafusion] mustafasrepo opened a new pull request, #6503: Bug fix, First accumulator multiple batch aware
mustafasrepo opened a new pull request, #6503:
URL: https://github.com/apache/arrow-datafusion/pull/6503
# Which issue does this PR close?
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Closes [#6502](https://github.com/apache/arrow-datafusion/issues/6502).
# Rationale for this change
Previously first_value accumulator was giving the first value of the last batch received as result. It wasn't aware of whether first_value was set at previous batches or not. Hence when working with multiple batch data the results produced were wrong. This PR fixes this problem.
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# What changes are included in this PR?
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# Are these changes tested?
Yes, new unit test is added for this new behavior.
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# Are there any user-facing changes?
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[GitHub] [arrow-datafusion] alamb commented on pull request #6503: Bug fix, First accumulator multiple batch aware
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on PR #6503:
URL: https://github.com/apache/arrow-datafusion/pull/6503#issuecomment-1570935029
Thanks @mustafasrepo
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[GitHub] [arrow-datafusion] alamb commented on a diff in pull request #6503: Bug fix, First accumulator multiple batch aware
Posted by "alamb (via GitHub)" <gi...@apache.org>.
alamb commented on code in PR #6503:
URL: https://github.com/apache/arrow-datafusion/pull/6503#discussion_r1212296445
##########
datafusion/physical-expr/src/aggregate/first_last.rs:
##########
@@ -112,25 +112,35 @@ impl PartialEq<dyn Any> for FirstValue {
#[derive(Debug)]
struct FirstValueAccumulator {
first: ScalarValue,
+ // At the beginning, `is_set` is `false`, this means `first` is not seen yet.
+ // Once we see (`is_set=true`) first value, we do not update `first`.
+ is_set: bool,
Review Comment:
Another potential way that might let the compiler check that `is_set` was updated correctly would be something like:
```
struct FirstValueAccumulator {
/// None until the data has been seen
first: Option<ScalarValue>
}
```
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[GitHub] [arrow-datafusion] mustafasrepo commented on a diff in pull request #6503: Bug fix, First accumulator multiple batch aware
Posted by "mustafasrepo (via GitHub)" <gi...@apache.org>.
mustafasrepo commented on code in PR #6503:
URL: https://github.com/apache/arrow-datafusion/pull/6503#discussion_r1212317393
##########
datafusion/physical-expr/src/aggregate/first_last.rs:
##########
@@ -112,25 +112,35 @@ impl PartialEq<dyn Any> for FirstValue {
#[derive(Debug)]
struct FirstValueAccumulator {
first: ScalarValue,
+ // At the beginning, `is_set` is `false`, this means `first` is not seen yet.
+ // Once we see (`is_set=true`) first value, we do not update `first`.
+ is_set: bool,
Review Comment:
I have considered this option, however, during `evaluate` call if `first` is `None`. We need to return `NULL` for appropriate type, such as `ScalarValue::Int64(None)` if type is `Int64`. However, datatype is only available during initialization. If we want to use `Option` for `first`, we may need to store data type also. Hence I opted for this approach
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[GitHub] [arrow-datafusion] mustafasrepo merged pull request #6503: Bug fix, First accumulator multiple batch aware
Posted by "mustafasrepo (via GitHub)" <gi...@apache.org>.
mustafasrepo merged PR #6503:
URL: https://github.com/apache/arrow-datafusion/pull/6503
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