cloud-fan opened a new pull request #25180: [SPARK-28423][SQL] merge Scan and 
Batch/Stream
URL: https://github.com/apache/spark/pull/25180
 
 
   ## What changes were proposed in this pull request?
   
   By design, `Scan` represents a logical data scan, `Batch`/`Stream` 
represents a physical data scan.
   
   However, this doesn't match reality. The logical 
plan(`DataSourceV2Relation`) contains `Table` and the phyiscal 
plan(`BatchScanExec` and friends) contains `Batch`/`Stream`. The operator 
pushdown happens at planning time, so `Scan` and `Batch`/`Stream` are always 
created together in the planner rules. That said, `Table` is the actual logical 
data scan.
   
   Since there is not much can be separated from `Scan` and `Batch`/`Stream`, 
almost all the existing DS v2 implementations either implement `Scan` and 
`Batch`/`Stream` together, or use anonymous class to implement `Scan`.
   
   In addition, the write side API has no such separation either: it's just 
`WriterBuilder` -> `BatchWrite`/`StreamingWrite`.
   
   This PR proposes to merge `Scan` and `Batch`/`Stream`, to match the write 
side API: `ScanBuilder` -> `BatchScan`/`MicroBatchScan`/`ContinuousScan`.
   
   ## How was this patch tested?
   
   existing tests
   

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