ZENOTME commented on PR #135:
URL: https://github.com/apache/iceberg-rust/pull/135#issuecomment-1894811712
> Trait is usually used to abstract things and hide concrete implementation.
I don't quite understand the goal of this trait CurrentStatus and when it will
be useful?
Sorry, Let me try to illustrate more clearly. Let me use a example to
illustrate it:
We may have kinds of partition writer in the future: fanout partition writer
will compute the partition and dispatcher them and precompute partition writer
will accept the data with the partition value computed before. But both of them
will expose the same metrics `PartitionMetrics`. Like following:
```
struct PartitionMetrics {
partition_num: usize
}
struct FanoutPartitionWriter
impl CurrentStatus<PartitionMetrics> for FanoutPartitionWriter
struct PrecomputePartitionWriter
impl CurrentStatus<PartitionMetrics> for PrecomputePartitionWriter
```
And through `CurrentStatus<PartitionMetrics>`, we can write a metrics
monitor writer and accept both of them as a input.
```
struct PartitionMetricsMonitorWriter<W: IcebergWriter +
CurrentStatus<PartitionMetrics>> {
writer: W
}
```
### Do we have another way?
Yes, we also can do like this:
```
pub trait CurrentFileStatus {
/// Get the current file path.
fn current_file_path(&self) -> String;
/// Get the current file row number.
fn current_row_num(&self) -> usize;
/// Get the current file written size.
fn current_written_size(&self) -> usize;
}
trait CurrentPartitionMetrics {
fn metrics() -> PartitionMetrics;
}
trait CurrentDataFileWriterMetrics {
fn metrics() -> DataFileWriterMetrics
}
```
But I feel that all these traits can be abstract as `pub trait
CurrentStatus<T>` so that instead of defining more traits, we can just define
more data types in the future. The benefit of this may not be obvious. So both
of way look good to me.
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