[SPARK-9228] [SQL] use tungsten.enabled in public for both of codegen/unsafe

spark.sql.tungsten.enabled will be the default value for both codegen and unsafe, they are kept internally for debug/testing.

cc marmbrus rxin

Author: Davies Liu <davies@databricks.com>

Closes #7998 from davies/tungsten and squashes the following commits:

c1c16da [Davies Liu] update doc
1a47be1 [Davies Liu] use tungsten.enabled for both of codegen/unsafe

(cherry picked from commit 4e70e8256ce2f45b438642372329eac7b1e9e8cf)
Signed-off-by: Reynold Xin <rxin@databricks.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/docs/sql-programming-guide.md b/docs/sql-programming-guide.md
index 3ea77e8242..6c317175d3 100644
--- a/docs/sql-programming-guide.md
+++ b/docs/sql-programming-guide.md
@@ -1884,11 +1884,11 @@ that these options will be deprecated in future release as more optimizations ar
     </td>
   </tr>
   <tr>
-    <td><code>spark.sql.codegen</code></td>
+    <td><code>spark.sql.tungsten.enabled</code></td>
     <td>true</td>
     <td>
-      When true, code will be dynamically generated at runtime for expression evaluation in a specific
-      query. For some queries with complicated expression this option can lead to significant speed-ups.
+      When true, use the optimized Tungsten physical execution backend which explicitly manages memory
+      and dynamically generates bytecode for expression evaluation.
     </td>
   </tr>
   <tr>