WinkerDu opened a new pull request, #2405:
URL: https://github.com/apache/arrow-datafusion/pull/2405
# Which issue does this PR close?
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Closes #2404 .
# Rationale for this change
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the issue then this section is not needed.
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For now, DataFusion hasn't support `sum(distinct)` yet. Though optimizer
`SingleDistinctToGroupBy` (#1315) supports single distinct usage, there are
more SQL scenes have not been covered.
For example, run the following unit test,
```
#[tokio::test]
async fn query_sum_distinct() -> Result<()> {
let schema = Arc::new(Schema::new(vec![
Field::new("c1", DataType::Int64, true),
Field::new("c2", DataType::Int64, true),
]));
let data = RecordBatch::try_new(
schema.clone(),
vec![
Arc::new(Int64Array::from(vec![
Some(0),
Some(1),
None,
Some(3),
Some(3),
])),
Arc::new(Int64Array::from(vec![
None,
Some(1),
Some(1),
Some(2),
Some(2),
])),
],
)?;
let table = MemTable::try_new(schema, vec![vec![data]])?;
let ctx = SessionContext::new();
ctx.register_table("test", Arc::new(table))?;
let sql = "SELECT AVG(c1), SUM(DISTINCT c2) FROM test";
let actual = execute_to_batches(&ctx, sql).await;
Ok(())
}
```
then error raises like
```
NotImplemented(\"SUM(DISTINCT) aggregations are not available\") at Creating
physical plan for 'SELECT AVG(c1), SUM(DISTINCT c2) FROM test': Projection:
#AVG(test.c1), #SUM(DISTINCT test.c2)\n Aggregate: groupBy=[[]],
aggr=[[AVG(#test.c1), SUM(DISTINCT #test.c2)]]\n TableScan: test
projection=Some([0, 1])
```
# What changes are included in this PR?
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There is no need to duplicate the description in the issue here but it is
sometimes worth providing a summary of the individual changes in this PR.
-->
Introduces `expressions::DistinctSum` into DF
- Maintains a `HashSet` to record unique numeric list, update `HashSet` when
new item input.
- Aggregate state stores in `ScalarValue::List`, which Built from `HashSet`.
- During Final aggregate, evaluate `DistinctSum` by computing sum from
numeric stored in `HashSet`
# Are there any user-facing changes?
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updated before approving the PR.
-->
No.
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change` label.
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