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DeltaCDFRelation
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jaceklaskowski committed Jul 2, 2024
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`DeltaCDFRelation` is created when:

* `CDCReaderImpl` is requested for a [CDF-aware BaseRelation](CDCReaderImpl.md#getCDCRelation)
* `CDCReaderImpl` is requested for a [CDF-aware BaseRelation](CDCReaderImpl.md#getCDCRelation) and [emptyCDFRelation](CDCReaderImpl.md#emptyCDFRelation)

## Building Distributed Scan { #buildScan }

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`buildScan` does column pruning with the `requiredColumns` defined (using `Dataset.select` operator).

In the end, `buildScan` converts the `DataFrame` to `RDD[Row]` (using `DataFrame.rdd` operator).

## Schema

??? note "BaseRelation"

```scala
schema: StructType
```

`schema` is part of the `BaseRelation` ([Spark SQL]({{ book.spark_sql }}/BaseRelation/#schema)) abstraction.

`schema` [cdcReadSchema](CDCReaderImpl.md#cdcReadSchema) for the [schema](../Metadata.md#schema) of the delta table (based on the [Metadata](../Snapshot.md#metadata) of the [snapshotForBatchSchema](#snapshotForBatchSchema)).

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