DataFrame::write_table return type is documented incorrectly

[mlilback]

Describe the bug

The documentation for DataFrame:write_table says returning the count of rows written but it returns Result<Vec<RecordBatch>, DataFusionError>.

To Reproduce

No response

Expected behavior

No response

Additional context

No response

[devinjdangelo]

The Vec that is returned will contain a single RecordBatch with a single Row and Column, which is the count of rows written.

Result<Vec> is the return type since under the hood write table calls collect() which collects a stream of RecordBatchs into a Vec. It just so happens this specific plan will only return a single recordbatch with a single value.

Since we know InsertExec will only return a single value, we could extract that value and cast to usize. Alternatively, we could expand the documentation to make this more clear.

[devinjdangelo]

@mlilback I opened a PR to update this documentation to hopefully make it more clear!

This method ultimately runs an execution plan returned by an arbitrary dyn TableProvider, so it is true we should not state so plainly that this method will always return the count of rows inserted. It depends on the specific TableProvider registered for the table passed.

I updated the docs to reflect this nuance in the PR.