Implement simple RecordBatchReader

[wjones127]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

As part of ADBC API, we need to produce RecordBatchReader from data. I wasn't able to find any existing struct that produces one from a RecordBatch or Vec<RecordBatch>. Would be happy to hear if I am mistaken! Otherwise, happy to submit a PR for this.

Describe the solution you'd like

Probably something like:

struct SimpleRecordBatchReader { ... }

impl SimpleRecordBatchReader {
    pub fn new(batches: Vec<RecordBatch>, schema: SchemaRef) -> Self;
}

Describe alternatives you've considered

Open to any alternatives.

Additional context

[tustvold]

What do you think of a generic RecordBatchIterator<I> that can be created from I: IntoIterator<Item=Result<RecordBatch>> and a corresponding Schema and implement RecordBatchReader? I think this would cover the in-memory use-case you describe, as well as streaming versions?

[wjones127]

That sounds even better!