[SPARK-8610] [SQL] Separate Row and InternalRow (part 2)

Currently, we use GenericRow both for Row and InternalRow, which is confusing because it could contain Scala type also Catalyst types.

This PR changes to use GenericInternalRow for InternalRow (contains catalyst types), GenericRow for Row (contains Scala types).

Also fixes some incorrect use of InternalRow or Row.

Author: Davies Liu <davies@databricks.com>

Closes apache#7003 from davies/internalrow and squashes the following commits:

d05866c [Davies Liu] fix test: rollback changes for pyspark
72878dd [Davies Liu] Merge branch 'master' of github.com:apache/spark into internalrow
efd0b25 [Davies Liu] fix copy of MutableRow
87b13cf [Davies Liu] fix test
d2ebd72 [Davies Liu] fix style
eb4b473 [Davies Liu] mark expensive API as final
bd4e99c [Davies Liu] Merge branch 'master' of github.com:apache/spark into internalrow
bdfb78f [Davies Liu] remove BaseMutableRow
6f99a97 [Davies Liu] fix catalyst test
defe931 [Davies Liu] remove BaseRow
288b31f [Davies Liu] Merge branch 'master' of github.com:apache/spark into internalrow
9d24350 [Davies Liu] separate Row and InternalRow (part 2)

sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/UnsafeRow.java

@@ -23,16 +23,12 @@
 import java.util.HashSet;
 import java.util.Set;
 
-import scala.collection.Seq;
-import scala.collection.mutable.ArraySeq;
-
 import org.apache.spark.sql.catalyst.InternalRow;
-import org.apache.spark.sql.BaseMutableRow;
 import org.apache.spark.sql.types.DataType;
 import org.apache.spark.sql.types.StructType;
-import org.apache.spark.unsafe.types.UTF8String;
 import org.apache.spark.unsafe.PlatformDependent;
 import org.apache.spark.unsafe.bitset.BitSetMethods;
+import org.apache.spark.unsafe.types.UTF8String;
 
 import static org.apache.spark.sql.types.DataTypes.*;
 
@@ -52,7 +48,7 @@
  *
  * Instances of `UnsafeRow` act as pointers to row data stored in this format.
  */
-public final class UnsafeRow extends BaseMutableRow {
+public final class UnsafeRow extends MutableRow {
 
   private Object baseObject;
   private long baseOffset;
@@ -63,6 +59,8 @@ public final class UnsafeRow extends BaseMutableRow {
   /** The number of fields in this row, used for calculating the bitset width (and in assertions) */
   private int numFields;
 
+  public int length() { return numFields; }
+
   /** The width of the null tracking bit set, in bytes */
   private int bitSetWidthInBytes;
   /**
@@ -344,13 +342,4 @@ public InternalRow copy() {
   public boolean anyNull() {
     return BitSetMethods.anySet(baseObject, baseOffset, bitSetWidthInBytes);
   }
-
-  @Override
-  public Seq<Object> toSeq() {
-    final ArraySeq<Object> values = new ArraySeq<Object>(numFields);
-    for (int fieldNumber = 0; fieldNumber < numFields; fieldNumber++) {
-      values.update(fieldNumber, get(fieldNumber));
-    }
-    return values;
-  }
 }