[SPARK-8961] [SQL] Makes BaseWriterContainer.outputWriterForRow accepts InternalRow instead of Row

[liancheng]

This is a follow-up of SPARK-8888, which also aims to optimize writing dynamic partitions.

Three more changes can be made here:

1. Using InternalRow instead of Row in BaseWriterContainer.outputWriterForRow
2. Using Cast expressions to convert partition columns to strings, so that we can leverage code generation.
3. Replacing the FP-style zip and map calls with a faster imperative while loop.

[SparkQA]

Test build #36970 has finished for PR 7331 at commit 719e63b.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[liancheng]

cc @rxin

[rxin]

I explicitly didn't include this wildcard implicit import because I didn't want future code to accidentally introduce a scala wrapper on the java hashmap.

[liancheng]

Got it. Converting the iterator explicitly now.

[rxin]

lgtm

[SparkQA]

Test build #37062 has finished for PR 7331 at commit b5ab9ae.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[rxin]

Thanks - merging.

[rxin]

Actually couldn't merge. Not sure what's going on.

Proceed with merging pull request #7331? (y/n): y
git fetch apache-github pull/7331/head:PR_TOOL_MERGE_PR_7331
git fetch apache master:PR_TOOL_MERGE_PR_7331_MASTER
git checkout PR_TOOL_MERGE_PR_7331_MASTER
error: you need to resolve your current index first
Traceback (most recent call last):
  File "./merge_spark_pr.py", line 331, in <module>
    merge_hash = merge_pr(pr_num, target_ref)
  File "./merge_spark_pr.py", line 109, in merge_pr
    run_cmd("git checkout %s" % target_branch_name)
  File "./merge_spark_pr.py", line 80, in run_cmd
    return subprocess.check_output(cmd.split(" "))
  File "/Users/rxin/anaconda/lib/python2.7/subprocess.py", line 573, in check_output
    raise CalledProcessError(retcode, cmd, output=output)
subprocess.CalledProcessError: Command '[u'git', u'checkout', u'PR_TOOL_MERGE_PR_7331_MASTER']' returned non-zero exit status 1

[liancheng]

Let me try to merge it.

[liancheng]

Merged to master.