How can I tell if a record in a bounded job is the last record?

[Yik San Chan]

Hi community,

I have a batch job that consumes records from a bounded source (e.g.,
Hive), walk them through a BufferingSink as described in [docs](
https://ci.apache.org/projects/flink/flink-docs-release-1.13/docs/dev/datastream/fault-tolerance/state/#checkpointedfunction).
In the BufferingSink, I want to flush out records to the sink in
1000-record batches.

Given the source is bounded, I will need to flush out all records when it
comes to the end, otherwise records buffered (variable bufferedElements)
will be lost.

An obvious way of doing so is to flush out all records in the `close`
method. That should work fine.

However, I wonder if it's possible to tell if a record is the last record
in the `invoke` method? In other words, how to implement the `isLastRecord`
method below?

```java
@Override public void invoke(Tuple2<String, Integer> value, Context
context) throws Exception {
    bufferedElements.add(value);
    if (bufferedElements.size() == threshold || isLastRecord()) {
        for (Tuple2<String, Integer> element: bufferedElements) {
            // send it to the sink
        }
        bufferedElements.clear();
    }
}
```

Thanks!

Best,
Yik San