panic! 'index out of bounds: the len is 0 but the index is 0 with bad sql query

[alamb]

Describe the bug
A malformed query generates a panic rather than an error

To Reproduce

echo "true" > /tmp/foo.csv
cargo run -p datafusion-cli  --no-default-features

Then run select count(distinct) from foo; via sql:

> CREATE EXTERNAL TABLE foo(bar boolean)
STORED AS CSV
LOCATION '/tmp/foo.csv';
0 rows in set. Query took 0 seconds.
> select count(distinct) from foo;
thread 'main' panicked at 'index out of bounds: the len is 0 but the index is 0', datafusion/src/physical_plan/aggregates.rs:116:15
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Expected behavior
I expect an error about "no column specified for count distinct" rather than a panic

[jgoday]

Hi @alamb Can I try this ?
Should be enough to check if the coerced args in the aggregation returns no result (in physical_plan/aggregates) ?

let arg = coerce(args, input_schema, &signature(fun))?;
if arg.len() == 0 {
    return Err(DataFusionError::Plan(format!(
        "Invalid aggregation '{}'",
        name,
    )));
}

[alamb]

Thanks @jgoday ! Perhaps you can make the error a little more specific -- like "no arguments passed to aggregate {}" or something. But the location looks reasonable

[jgoday]

Thank you @alamb. I have created a PR #505 for this.
How about this error message?

Aggregate error. Invalid or wrong number of arguments passed to aggregate: {}

[alamb]

I think "Invalid or wrong number of arguments passed to aggregate: {}" is probably sufficient