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xiepengjie authored and srowen committed 523e238 Jul 9, 2020
### What changes were proposed in this pull request?

When somebody changed the type of partition's field, spark will throw ClassCastException. For example, we have a table like this:
```
drop table if exists cast_exception_test;

create table cast_exception_test(c1 int, c2 string) partitioned by (dt string) stored as orc;

insert into table cast_exception_test partition(dt='2020-04-08') values('1', 'jeff_1');
```

If you change the field's type in hive, query the old partition, spark will throw ClassCastException, but hive will not:
```
-- change the field's type using hive
alter table cast_exception_test change column c1 c1 string;
-- hive correct,  but spark throws ClassCastException
select * from cast_exception_test where dt='2020-04-08';
```

### Why are the changes needed?

When the table has many fields, we don's known which field has been changed. If we print out log about this exception, it will very helpful for us to troubleshoot.

### Does this PR introduce _any_ user-facing change?

When the ClassCastException is caused by changed field's type, you can search which field has problem in exexutor logs:
```
20/04/09 17:22:05 ERROR hive.HadoopTableReader: Exception thrown in field <c1>
```

### How was this patch tested?

First, prepare the test data, the table is partitioned and stored as orc:
```
drop table if exists cast_exception_test;
create table cast_exception_test(c1 int, c2 string) partitioned by (dt string) stored as orc;
insert into table cast_exception_test partition(dt='2020-04-08') values('1', 'jeff_1');
```

Then, change the field's type in hive.
```
alter table cast_exception_test change column c1 c1 string;
```

Now the metadata of the table has been modified, but the partition's metadata which is stored in orc file or hive metastore's mysql is still old. So, query command throws ClassCastException in spark, because spark use table's metadata which is different from orc file's metadata. But hive use partition's metadata which is the same as orc file's metadata.

If you query the old partition, spark will thrown ClassCastException, but hive will not:
```
select * from cast_exception_test where dt='2020-04-08';
```

Closes #29010 from StefanXiepj/SPARK-32192.

Authored-by: xiepengjie <xiepengjie@didiglobal.com>
Signed-off-by: Sean Owen <srowen@gmail.com>

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README.md

Apache Spark

Spark is a unified analytics engine for large-scale data processing. 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 Structured Streaming for stream processing.

https://spark.apache.org/

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Online Documentation

You can find the latest Spark documentation, including a programming guide, on the project web page. 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.)

More detailed documentation is available from the project site, at "Building Spark".

For general development tips, including info on developing Spark using an IDE, see "Useful Developer Tools".

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 1,000,000,000:

scala> spark.range(1000 * 1000 * 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 1,000,000,000:

>>> spark.range(1000 * 1000 * 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.

There is also a Kubernetes integration test, see resource-managers/kubernetes/integration-tests/README.md

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 and Enabling YARN" 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.

Contributing

Please review the Contribution to Spark guide for information on how to get started contributing to the project.

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