Added LZ4 to compression codec in configuration page.

Author: Reynold Xin <rxin@apache.org>

Closes #1417 from rxin/lz4 and squashes the following commits:

472f6a1 [Reynold Xin] Set the proper default.
9cf0b2f [Reynold Xin] Added LZ4 to compression codec in configuration page.
[SPARK-2471] remove runtime scope for jets3t

The assembly jar (built by sbt) doesn't include jets3t if we set it to runtime only, but I don't know whether it was set this way for a particular reason.

CC: srowen ScrapCodes

Author: Xiangrui Meng <meng@databricks.com>

Closes #1402 from mengxr/jets3t and squashes the following commits:

bfa2d17 [Xiangrui Meng] remove runtime scope for jets3t
[SPARK-2483][SQL] Fix parsing of repeated, nested data access.

Author: Michael Armbrust <michael@databricks.com>

Closes #1411 from marmbrus/nestedRepeated and squashes the following commits:

044fa09 [Michael Armbrust] Fix parsing of repeated, nested data access.
[SQL] Whitelist more Hive tests.

Author: Michael Armbrust <michael@databricks.com>

Closes #1396 from marmbrus/moreTests and squashes the following commits:

6660b60 [Michael Armbrust] Blacklist a test that requires DFS command.
8b6001c [Michael Armbrust] Add golden files.
ccd8f97 [Michael Armbrust] Whitelist more tests.
[SPARK-2474][SQL] For a registered table in OverrideCatalog, the Analyzer failed to resolve references in the format of "tableName.fieldName"

Please refer to JIRA (https://issues.apache.org/jira/browse/SPARK-2474) for how to reproduce the problem and my understanding of the root cause.

Author: Yin Huai <huai@cse.ohio-state.edu>

Closes #1406 from yhuai/SPARK-2474 and squashes the following commits:

96b1627 [Yin Huai] Merge remote-tracking branch 'upstream/master' into SPARK-2474
af36d65 [Yin Huai] Fix comment.
be86ba9 [Yin Huai] Correct SQL console settings.
c43ad00 [Yin Huai] Wrap the relation in a Subquery named by the table name in OverrideCatalog.lookupRelation.
a5c2145 [Yin Huai] Support sql/console.
SPARK-2407: Added internal implementation of SQL SUBSTR()

This replaces the Hive UDF for SUBSTR(ING) with an implementation in Catalyst
and adds tests to verify correct operation.

Author: William Benton <willb@redhat.com>

Closes #1359 from willb/internalSqlSubstring and squashes the following commits:

ccedc47 [William Benton] Fixed too-long line.
a30a037 [William Benton] replace view bounds with implicit parameters
ec35c80 [William Benton] Adds fixes from review:
4f3bfdb [William Benton] Added internal implementation of SQL SUBSTR()
[SQL] Attribute equality comparisons should be done by exprId.

Author: Michael Armbrust <michael@databricks.com>

Closes #1414 from marmbrus/exprIdResolution and squashes the following commits:

97b47bc [Michael Armbrust] Attribute equality comparisons should be done by exprId.
[SPARK-2498] [SQL] Synchronize on a lock when using scala reflection inside data type objects.

JIRA ticket: https://issues.apache.org/jira/browse/SPARK-2498

Author: Zongheng Yang <zongheng.y@gmail.com>

Closes #1423 from concretevitamin/scala-ref-catalyst and squashes the following commits:

325a149 [Zongheng Yang] Synchronize on a lock when initializing data type objects in Catalyst.
[SPARK-2469] Use Snappy (instead of LZF) for default shuffle compression codec

This reduces shuffle compression memory usage by 3x.

Author: Reynold Xin <rxin@apache.org>

Closes #1415 from rxin/snappy and squashes the following commits:

06c1a01 [Reynold Xin] SPARK-2469: Use Snappy (instead of LZF) for default shuffle compression codec.
[SPARK-2500] Move the logInfo for registering BlockManager to BlockManagerMasterActor.register method

PR for SPARK-2500

Move the logInfo call for BlockManager to BlockManagerMasterActor.register instead of BlockManagerInfo constructor.

Previously the loginfo call for registering the registering a BlockManager is happening in the BlockManagerInfo constructor. This kind of confusing because the code could call "new BlockManagerInfo" without actually registering a BlockManager and could confuse when reading the log files.

Author: Henry Saputra <henry.saputra@gmail.com>

Closes #1424 from hsaputra/move_registerblockmanager_log_to_registration_method and squashes the following commits:

3370b4a [Henry Saputra] Move the loginfo for BlockManager to BlockManagerMasterActor.register instead of BlockManagerInfo constructor.
follow pep8 None should be compared using is or is not

http://legacy.python.org/dev/peps/pep-0008/
## Programming Recommendations
- Comparisons to singletons like None should always be done with is or is not, never the equality operators.

Author: Ken Takagiwa <ken@Kens-MacBook-Pro.local>

Closes #1422 from giwa/apache_master and squashes the following commits:

7b361f3 [Ken Takagiwa] follow pep8 None should be checked using is or is not
[SPARK-2314][SQL] Override collect and take in JavaSchemaRDD, forwarding to SchemaRDD implementations.

Author: Aaron Staple <aaron.staple@gmail.com>

Closes #1421 from staple/SPARK-2314 and squashes the following commits:

73e04dc [Aaron Staple] [SPARK-2314] Override collect and take in JavaSchemaRDD, forwarding to SchemaRDD implementations.
[SPARK-2509][SQL] Add optimization for Substring.

`Substring` including `null` literal cases could be added to `NullPropagation`.

Author: Takuya UESHIN <ueshin@happy-camper.st>

Closes #1428 from ueshin/issues/SPARK-2509 and squashes the following commits:

d9eb85f [Takuya UESHIN] Add Substring cases to NullPropagation.
[SPARK-2504][SQL] Fix nullability of Substring expression.

This is a follow-up of #1359 with nullability narrowing.

Author: Takuya UESHIN <ueshin@happy-camper.st>

Closes #1426 from ueshin/issues/SPARK-2504 and squashes the following commits:

5157832 [Takuya UESHIN] Remove unnecessary white spaces.
80958ac [Takuya UESHIN] Fix nullability of Substring expression.
[SPARK-2119][SQL] Improved Parquet performance when reading off S3

JIRA issue: [SPARK-2119](https://issues.apache.org/jira/browse/SPARK-2119)

Essentially this PR fixed three issues to gain much better performance when reading large Parquet file off S3.

1. When reading the schema, fetching Parquet metadata from a part-file rather than the `_metadata` file

   The `_metadata` file contains metadata of all row groups, and can be very large if there are many row groups. Since schema information and row group metadata are coupled within a single Thrift object, we have to read the whole `_metadata` to fetch the schema. On the other hand, schema is replicated among footers of all part-files, which are fairly small.

1. Only add the root directory of the Parquet file rather than all the part-files to input paths

   HDFS API can automatically filter out all hidden files and underscore files (`_SUCCESS` & `_metadata`), there's no need to filter out all part-files and add them individually to input paths. What make it much worse is that, `FileInputFormat.listStatus()` calls `FileSystem.globStatus()` on each individual input path sequentially, each results a blocking remote S3 HTTP request.

1. Worked around [PARQUET-16](https://issues.apache.org/jira/browse/PARQUET-16)

   Essentially PARQUET-16 is similar to the above issue, and results lots of sequential `FileSystem.getFileStatus()` calls, which are further translated into a bunch of remote S3 HTTP requests.

   `FilteringParquetRowInputFormat` should be cleaned up once PARQUET-16 is fixed.

Below is the micro benchmark result. The dataset used is a S3 Parquet file consists of 3,793 partitions, about 110MB per partition in average. The benchmark is done with a 9-node AWS cluster.

- Creating a Parquet `SchemaRDD` (Parquet schema is fetched)

  ```scala
  val tweets = parquetFile(uri)
  ```

  - Before: 17.80s
  - After: 8.61s

- Fetching partition information

  ```scala
  tweets.getPartitions
  ```

  - Before: 700.87s
  - After: 21.47s

- Counting the whole file (both steps above are executed altogether)

  ```scala
  parquetFile(uri).count()
  ```

  - Before: ??? (haven't test yet)
  - After: 53.26s

Author: Cheng Lian <lian.cs.zju@gmail.com>

Closes #1370 from liancheng/faster-parquet and squashes the following commits:

94a2821 [Cheng Lian] Added comments about schema consistency
d2c4417 [Cheng Lian] Worked around PARQUET-16 to improve Parquet performance
1c0d1b9 [Cheng Lian] Accelerated Parquet schema retrieving
5bd3d29 [Cheng Lian] Fixed Parquet log level
SPARK-2277: make TaskScheduler track hosts on rack

Hi mateiz, I've created [SPARK-2277](https://issues.apache.org/jira/browse/SPARK-2277) to make TaskScheduler track hosts on each rack. Please help to review, thanks.

Author: Rui Li <rui.li@intel.com>

Closes #1212 from lirui-intel/trackHostOnRack and squashes the following commits:

2b4bd0f [Rui Li] SPARK-2277: refine UT
fbde838 [Rui Li] SPARK-2277: add UT
7bbe658 [Rui Li] SPARK-2277: rename the method
5e4ef62 [Rui Li] SPARK-2277: remove unnecessary import
79ac750 [Rui Li] SPARK-2277: make TaskScheduler track hosts on rack
Tightening visibility for various Broadcast related classes.

In preparation for SPARK-2521.

Author: Reynold Xin <rxin@apache.org>

Closes #1438 from rxin/broadcast and squashes the following commits:

432f1cc [Reynold Xin] Tightening visibility for various Broadcast related classes.
[SPARK-2525][SQL] Remove as many compilation warning messages as possible in Spark SQL

JIRA: https://issues.apache.org/jira/browse/SPARK-2525.

Author: Yin Huai <huai@cse.ohio-state.edu>

Closes #1444 from yhuai/SPARK-2517 and squashes the following commits:

edbac3f [Yin Huai] Removed some compiler type erasure warnings.
[SQL] Cleaned up ConstantFolding slightly.

Moved couple rules out of NullPropagation and added more comments.

Author: Reynold Xin <rxin@apache.org>

Closes #1430 from rxin/sql-folding-rule and squashes the following commits:

7f9a197 [Reynold Xin] Updated documentation for ConstantFolding.
7f8cf61 [Reynold Xin] [SQL] Cleaned up ConstantFolding slightly.
SPARK-2519. Eliminate pattern-matching on Tuple2 in performance-critical...

... aggregation code

Author: Sandy Ryza <sandy@cloudera.com>

Closes #1435 from sryza/sandy-spark-2519 and squashes the following commits:

640706a [Sandy Ryza] SPARK-2519. Eliminate pattern-matching on Tuple2 in performance-critical aggregation code