jonmmease opened a new issue, #4828:
URL: https://github.com/apache/arrow-datafusion/issues/4828
**Describe the bug**
This is a MRE for a query that results in this error:
```
InvalidArgumentError("Column 'COUNT(DISTINCT tbl.col2)[count distinct]' is
declared as non-nullable but contains null values")
```
The input table (`tbl`) looks like this:
```
+------+------+
| col1 | col2 |
+------+------+
| A | |
| B | b |
| C | c |
+------+------+
```
This is the query
```sql
SELECT count(DISTINCT "col2"), min(0) AS "zero"
FROM "tbl"
GROUP BY "col1"
```
The error goes away without the `min(0) AS "zero"` column expression
**To Reproduce**
Steps to reproduce the behavior:
```rust
#[cfg(test)]
mod tests {
use std::sync::Arc;
use datafusion::arrow::array::{ArrayRef, StringArray};
use datafusion::arrow::datatypes::{DataType, Field, Schema, SchemaRef};
use datafusion::arrow::record_batch::RecordBatch;
use datafusion::arrow::util::pretty::pretty_format_batches;
use datafusion::datasource::MemTable;
use datafusion::prelude::SessionContext;
#[tokio::test]
async fn count_distinct_error() {
let col1 = Arc::new(StringArray::from(
vec!["A", "B", "C"]
)) as ArrayRef;
let col2 = Arc::new(StringArray::from(
vec![None, Some("b"), Some("c")]
)) as ArrayRef;
let schema = Arc::new(Schema::new(vec![
Field::new("col1", DataType::Utf8, true),
Field::new("col2", DataType::Utf8, true)
])) as SchemaRef;
let batch = RecordBatch::try_new(schema.clone(), vec![col1,
col2]).unwrap();
let mem_table = MemTable::try_new(schema,
vec![vec![batch]]).unwrap();
// Create context and register table
let ctx = SessionContext::new();
ctx.register_table("tbl", Arc::new(mem_table)).unwrap();
// Print input table
let res = ctx.sql("SELECT * from
tbl").await.unwrap().collect().await.unwrap();
let formatted = pretty_format_batches(res.as_slice()).unwrap();
println!("{}", formatted);
// Perform query
let res = ctx.sql(r#"
SELECT count(DISTINCT "col2"), min(0) AS "zero"
FROM "tbl"
GROUP BY "col1"
"#).await.unwrap().collect().await.unwrap();
let formatted = pretty_format_batches(res.as_slice()).unwrap();
println!("{}", formatted);
}
}
```
**Expected behavior**
Expect the query to complete without errors
**Additional context**
This may be a duplicate of
https://github.com/apache/arrow-datafusion/issues/4040, but the query setup
there was more complex. If a maintainer thinks it's the same bug I'd be happy
to move this MRE over to that issue.
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