[SPARK-14237][SQL] De-duplicate partition value appending logic in various buildReader() implementations

## What changes were proposed in this pull request?

Currently, various `FileFormat` data sources share approximately the same code for partition value appending. This PR tries to eliminate this duplication.

A new method `buildReaderWithPartitionValues()` is added to `FileFormat` with a default implementation that appends partition values to `InternalRow`s produced by the reader function returned by `buildReader()`.

Special data sources like Parquet, which implements partition value appending inside `buildReader()` because of the vectorized reader, and the Text data source, which doesn't support partitioning, override `buildReaderWithPartitionValues()` and simply delegate to `buildReader()`.

This PR brings two benefits:

1. Apparently, it de-duplicates partition value appending logic

2. Now the reader function returned by `buildReader()` is only required to produce `InternalRow`s rather than `UnsafeRow`s if the data source doesn't override `buildReaderWithPartitionValues()`.

   Because the safe-to-unsafe conversion is also performed while appending partition values. This makes 3rd-party data sources (e.g. spark-avro) easier to implement since they no longer need to access private APIs involving `UnsafeRow`.

## How was this patch tested?

Existing tests should do the work.

Author: Cheng Lian <lian@databricks.com>

Closes #12866 from liancheng/spark-14237-simplify-partition-values-appending.

1 files changed, 1 insertions, 10 deletions

diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/orc/OrcRelation.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/orc/OrcRelation.scala
index d6a847f3ba..89d258e844 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/orc/OrcRelation.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/orc/OrcRelation.scala
@@ -157,20 +157,11 @@ private[sql] class DefaultSource
         }
 
         // Unwraps `OrcStruct`s to `UnsafeRow`s
-        val unsafeRowIterator = OrcRelation.unwrapOrcStructs(
+        OrcRelation.unwrapOrcStructs(
           conf,
           requiredSchema,
           Some(orcRecordReader.getObjectInspector.asInstanceOf[StructObjectInspector]),
           new RecordReaderIterator[OrcStruct](orcRecordReader))
-
-        // Appends partition values
-        val fullOutput = requiredSchema.toAttributes ++ partitionSchema.toAttributes
-        val joinedRow = new JoinedRow()
-        val appendPartitionColumns = GenerateUnsafeProjection.generate(fullOutput, fullOutput)
-
-        unsafeRowIterator.map { dataRow =>
-          appendPartitionColumns(joinedRow(dataRow, file.partitionValues))
-        }
       }
     }
   }