Apache Spark - A unified analytics engine for large-scale data processing
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Michael Allman 8f6cf00c69 [SPARK-15968][SQL] Nonempty partitioned metastore tables are not cached
(Please note this is a revision of PR #13686, which has been closed in favor of this PR.)

This PR addresses [SPARK-15968](https://issues.apache.org/jira/browse/SPARK-15968).

## What changes were proposed in this pull request?

The `getCached` method of [HiveMetastoreCatalog](https://github.com/apache/spark/blob/master/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala) computes `pathsInMetastore` from the metastore relation's catalog table. This only returns the table base path, which is incomplete/inaccurate for a nonempty partitioned table. As a result, cached lookups on nonempty partitioned tables always miss.

Rather than get `pathsInMetastore` from

    metastoreRelation.catalogTable.storage.locationUri.toSeq

I modified the `getCached` method to take a `pathsInMetastore` argument. Calls to this method pass in the paths computed from calls to the Hive metastore. This is how `getCached` was implemented in Spark 1.5:

e0c3212a9b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala (L444).

I also added a call in `InsertIntoHiveTable.scala` to invalidate the table from the SQL session catalog.

## How was this patch tested?

I've added a new unit test to `parquetSuites.scala`:

    SPARK-15968: nonempty partitioned metastore Parquet table lookup should use cached relation

Note that the only difference between this new test and the one above it in the file is that the new test populates its partitioned table with a single value, while the existing test leaves the table empty. This reveals a subtle, unexpected hole in test coverage present before this patch.

Note I also modified a different but related unit test in `parquetSuites.scala`:

    SPARK-15248: explicitly added partitions should be readable

This unit test asserts that Spark SQL should return data from a table partition which has been placed there outside a metastore query immediately after it is added. I changed the test so that, instead of adding the data as a parquet file saved in the partition's location, the data is added through a SQL `INSERT` query. I made this change because I could find no way to efficiently support partitioned table caching without failing that test.

In addition to my primary motivation, I can offer a few reasons I believe this is an acceptable weakening of that test. First, it still validates a fix for [SPARK-15248](https://issues.apache.org/jira/browse/SPARK-15248), the issue for which it was written. Second, the assertion made is stronger than that required for non-partitioned tables. If you write data to the storage location of a non-partitioned metastore table without using a proper SQL DML query, a subsequent call to show that data will not return it. I believe this is an intentional limitation put in place to make table caching feasible, but I'm only speculating.

Building a large `HadoopFsRelation` requires `stat`-ing all of its data files. In our environment, where we have tables with 10's of thousands of partitions, the difference between using a cached relation versus a new one is a matter of seconds versus minutes. Caching partitioned table metadata vastly improves the usability of Spark SQL for these cases.

Thanks.

Author: Michael Allman <michael@videoamp.com>

Closes #13818 from mallman/spark-15968.
2016-07-05 09:49:25 +08:00
.github [MINOR][MAINTENANCE] Fix typo for the pull request template. 2016-02-24 00:45:31 -08:00
assembly [SPARK-14925][BUILD] Re-introduce 'unused' dependency so that published POMs are flattened 2016-04-26 15:14:17 -07:00
bin [SPARK-15761][MLLIB][PYSPARK] Load ipython when default python is Python3 2016-07-01 09:27:34 +01:00
build [SPARK-14279][BUILD] Pick the spark version from pom 2016-06-06 09:42:50 -07:00
common [SPARK-16018][SHUFFLE] Shade netty to load shuffle jar in Nodemanger 2016-06-17 15:44:33 -05:00
conf [SPARK-15806][DOCUMENTATION] update doc for SPARK_MASTER_IP 2016-06-12 14:25:48 +01:00
core [MINOR][DOCS] Remove unused images; crush PNGs that could use it for good measure 2016-07-04 09:21:58 +01:00
data [GRAPHX][EXAMPLES] move graphx test data directory and update graphx document 2016-07-02 08:40:23 +01:00
dev [SPARK-15975] Fix improper Popen retcode code handling in dev/run-tests 2016-06-16 14:18:58 -07:00
docs [MINOR][DOCS] Remove unused images; crush PNGs that could use it for good measure 2016-07-04 09:21:58 +01:00
examples [SPARK-16260][ML][EXAMPLE] PySpark ML Example Improvements and Cleanup 2016-07-03 23:23:02 -07:00
external [SPARK-12177][STREAMING][KAFKA] limit api surface area 2016-07-01 00:53:36 -07:00
graphx [GRAPHX][EXAMPLES] move graphx test data directory and update graphx document 2016-07-02 08:40:23 +01:00
launcher [MINOR] Fix Java Lint errors introduced by #13286 and #13280 2016-06-08 14:51:00 +01:00
licenses [MINOR][BUILD] Add modernizr MIT license; specify "2014 and onwards" in license copyright 2016-06-04 21:41:27 +01:00
mllib [SPARK-14608][ML] transformSchema needs better documentation 2016-06-30 19:34:51 -07:00
mllib-local [MINOR] Fix Typos 'an -> a' 2016-06-06 09:35:47 +01:00
project [SPARK-16353][BUILD][DOC] Missing javadoc options for java unidoc 2016-07-04 21:16:17 +01:00
python [SPARK-16335][SQL] Structured streaming should fail if source directory does not exist 2016-07-01 15:16:04 -07:00
R [SPARK-16233][R][TEST] ORC test should be enabled only when HiveContext is available. 2016-07-01 15:35:19 -07:00
repl [SPARK-16125][YARN] Fix not test yarn cluster mode correctly in YarnClusterSuite 2016-06-24 08:28:32 +01:00
sbin [SPARK-15806][DOCUMENTATION] update doc for SPARK_MASTER_IP 2016-06-12 14:25:48 +01:00
sql [SPARK-15968][SQL] Nonempty partitioned metastore tables are not cached 2016-07-05 09:49:25 +08:00
streaming [SPARK-16129][CORE][SQL] Eliminate direct use of commons-lang classes in favor of commons-lang3 2016-06-24 10:35:54 +01:00
tools [MINOR][DOCS] Use multi-line JavaDoc comments in Scala code. 2016-04-02 17:50:40 -07:00
yarn [SPARK-16095][YARN] Yarn cluster mode should report correct state to SparkLauncher 2016-07-01 15:51:21 -07:00
.gitattributes [SPARK-3870] EOL character enforcement 2014-10-31 12:39:52 -07:00
.gitignore [SPARK-16128][SQL] Allow setting length of characters to be truncated to, in Dataset.show function. 2016-06-28 17:11:06 +05:30
.travis.yml [SPARK-15207][BUILD] Use Travis CI for Java Linter and JDK7/8 compilation test 2016-05-10 21:04:22 +01:00
CONTRIBUTING.md [SPARK-6889] [DOCS] CONTRIBUTING.md updates to accompany contribution doc updates 2015-04-21 22:34:31 -07:00
LICENSE [MINOR][BUILD] Add modernizr MIT license; specify "2014 and onwards" in license copyright 2016-06-04 21:41:27 +01:00
NOTICE [MINOR][BUILD] Add modernizr MIT license; specify "2014 and onwards" in license copyright 2016-06-04 21:41:27 +01:00
pom.xml [SPARK-12177][STREAMING][KAFKA] Update KafkaDStreams to new Kafka 0.10 Consumer API 2016-06-29 23:21:03 -07:00
README.md [SPARK-15821][DOCS] Include parallel build info 2016-06-14 13:59:01 +01:00
scalastyle-config.xml [SPARK-16129][CORE][SQL] Eliminate direct use of commons-lang classes in favor of commons-lang3 2016-06-24 10:35:54 +01:00

Apache Spark

Spark is a fast and general cluster computing system for Big Data. It provides high-level APIs in Scala, Java, Python, and R, and an optimized engine that supports general computation graphs for data analysis. It also supports a rich set of higher-level tools including Spark SQL for SQL and DataFrames, MLlib for machine learning, GraphX for graph processing, and Spark Streaming for stream processing.

http://spark.apache.org/

Online Documentation

You can find the latest Spark documentation, including a programming guide, on the project web page and project wiki. This README file only contains basic setup instructions.

Building Spark

Spark is built using Apache Maven. To build Spark and its example programs, run:

build/mvn -DskipTests clean package

(You do not need to do this if you downloaded a pre-built package.)

You can build Spark using more than one thread by using the -T option with Maven, see "Parallel builds in Maven 3". More detailed documentation is available from the project site, at "Building Spark". For developing Spark using an IDE, see Eclipse and IntelliJ.

Interactive Scala Shell

The easiest way to start using Spark is through the Scala shell:

./bin/spark-shell

Try the following command, which should return 1000:

scala> sc.parallelize(1 to 1000).count()

Interactive Python Shell

Alternatively, if you prefer Python, you can use the Python shell:

./bin/pyspark

And run the following command, which should also return 1000:

>>> sc.parallelize(range(1000)).count()

Example Programs

Spark also comes with several sample programs in the examples directory. To run one of them, use ./bin/run-example <class> [params]. For example:

./bin/run-example SparkPi

will run the Pi example locally.

You can set the MASTER environment variable when running examples to submit examples to a cluster. This can be a mesos:// or spark:// URL, "yarn" to run on YARN, and "local" to run locally with one thread, or "local[N]" to run locally with N threads. You can also use an abbreviated class name if the class is in the examples package. For instance:

MASTER=spark://host:7077 ./bin/run-example SparkPi

Many of the example programs print usage help if no params are given.

Running Tests

Testing first requires building Spark. Once Spark is built, tests can be run using:

./dev/run-tests

Please see the guidance on how to run tests for a module, or individual tests.

A Note About Hadoop Versions

Spark uses the Hadoop core library to talk to HDFS and other Hadoop-supported storage systems. Because the protocols have changed in different versions of Hadoop, you must build Spark against the same version that your cluster runs.

Please refer to the build documentation at "Specifying the Hadoop Version" for detailed guidance on building for a particular distribution of Hadoop, including building for particular Hive and Hive Thriftserver distributions.

Configuration

Please refer to the Configuration Guide in the online documentation for an overview on how to configure Spark.