[SPARK-9459] [SQL] use generated FromUnsafeProjection to do deep copy for UTF8String and struct

When accessing a column in UnsafeRow, it's good to avoid the copy, then we should do deep copy when turn the UnsafeRow into generic Row, this PR brings generated FromUnsafeProjection to do that.

This PR also fix the expressions that cache the UTF8String, which should also copy it.

Author: Davies Liu <davies@databricks.com>

Closes #7840 from davies/avoid_copy and squashes the following commits:

230c8a1 [Davies Liu] address comment
fd797c9 [Davies Liu] Merge branch 'master' of github.com:apache/spark into avoid_copy
e095dd0 [Davies Liu] rollback rename
8ef5b0b [Davies Liu] copy String in Columnar
81360b8 [Davies Liu] fix class name
9aecb88 [Davies Liu] use FromUnsafeProjection to do deep copy for UTF8String and struct

1 files changed, 12 insertions, 1 deletions

diff --git a/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java b/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
index 213dc761bb..916825d007 100644
--- a/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
+++ b/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
@@ -79,6 +79,17 @@ public final class UTF8String implements Comparable<UTF8String>, Serializable {
   }
 
   /**
+   * Creates an UTF8String from given address (base and offset) and length.
+   */
+  public static UTF8String fromAddress(Object base, long offset, int numBytes) {
+    if (base != null) {
+      return new UTF8String(base, offset, numBytes);
+    } else {
+      return null;
+    }
+  }
+
+  /**
    * Creates an UTF8String from String.
    */
   public static UTF8String fromString(String str) {
@@ -437,7 +448,7 @@ public final class UTF8String implements Comparable<UTF8String>, Serializable {
     while (i < numBytes) {
       int len = numBytesForFirstByte(getByte(i));
       copyMemory(this.base, this.offset + i, result,
-              BYTE_ARRAY_OFFSET + result.length - i - len, len);
+        BYTE_ARRAY_OFFSET + result.length - i - len, len);
 
       i += len;
     }