With 0a2b15ce43, the serialization stream and deserialization stream has enough information to determine it is handling a key-value pari, a key, or a value. It is safe to use `SparkSqlSerializer2` in more cases.
Author: Yin Huai <yhuai@databricks.com>
Closes#5849 from yhuai/serializer2MoreCases and squashes the following commits:
53a5eaa [Yin Huai] Josh's comments.
487f540 [Yin Huai] Use BufferedOutputStream.
8385f95 [Yin Huai] Always create a new row at the deserialization side to work with sort merge join.
c7e2129 [Yin Huai] Update tests.
4513d13 [Yin Huai] Use Serializer2 in more places.
(cherry picked from commit 3af423c92f)
Signed-off-by: Yin Huai <yhuai@databricks.com>
9d0d28940f