niebayes opened a new issue, #17269:
URL: https://github.com/apache/datafusion/issues/17269
### Describe the bug
Applying a UDAF on an empty table would return a non-empty result, a single
null value.
### To Reproduce
I have written a simple test for reproducing the bug. For any UDAF, such as
last_value and first_value, calling it on an empty table would give a result
containing a non empty result.
``` Rust
#[tokio::test]
async fn test_last_value() {
use std::sync::Arc;
use arrow_array::RecordBatch;
use arrow_schema::{DataType, Field, Schema};
use datafusion::assert_batches_eq;
use datafusion::physical_plan::collect;
use datafusion::prelude::SessionContext;
let schema = Arc::new(Schema::new(vec![
Field::new("id", DataType::Int32, false),
Field::new("value", DataType::Int32, false),
]));
let batch = RecordBatch::new_empty(schema);
let ctx = SessionContext::new();
ctx.register_batch("t", batch).unwrap();
let plan = ctx
.sql("select last_value(value order by id) from t")
.await
.unwrap()
.logical_plan()
.clone();
let exec_plan =
ctx.state().create_physical_plan(&plan).await.unwrap();
let batches = collect(exec_plan, ctx.task_ctx()).await.unwrap();
assert_eq!(batches.iter().map(|b| b.num_rows()).sum::<usize>(), 1);
assert_batches_eq!(
&[
"+----------------------------------------------------+",
"| last_value(t.value) ORDER BY [t.id ASC NULLS LAST] |",
"+----------------------------------------------------+",
"| |",
"+----------------------------------------------------+",
],
&batches
);
}
```
### Expected behavior
Calling a UDAF on an empty table should given an empty result.
### Additional context
_No response_
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