## What changes were proposed in this pull request?
The mapping of Spark schema to Avro schema is many-to-many. (See https://spark.apache.org/docs/latest/sql-data-sources-avro.html#supported-types-for-spark-sql---avro-conversion)
The default schema mapping might not be exactly what users want. For example, by default, a "string" column is always written as "string" Avro type, but users might want to output the column as "enum" Avro type.
With PR https://github.com/apache/spark/pull/21847, Spark supports user-specified schema in the batch writer.
For the function `to_avro`, we should support user-specified output schema as well.
## How was this patch tested?
Unit test.
Closes#25419 from gengliangwang/to_avro.
Authored-by: Gengliang Wang <gengliang.wang@databricks.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
## What changes were proposed in this pull request?
After [SPARK-26856](https://github.com/apache/spark/pull/23797), `Kinesis` Python UT fails with `Found multiple JARs` exception due to a wrong pattern.
- https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/104171/console
```
Exception: Found multiple JARs:
.../spark-streaming-kinesis-asl-assembly-3.0.0-SNAPSHOT.jar,
.../spark-streaming-kinesis-asl-assembly_2.12-3.0.0-SNAPSHOT.jar;
please remove all but one
```
It's because the pattern was changed in a wrong way.
**Original**
```python
kinesis_asl_assembly_dir, "target/scala-*/%s-*.jar" % name_prefix))
kinesis_asl_assembly_dir, "target/%s_*.jar" % name_prefix))
```
**After SPARK-26856**
```python
project_full_path, "target/scala-*/%s*.jar" % jar_name_prefix))
project_full_path, "target/%s*.jar" % jar_name_prefix))
```
The actual kinesis assembly jar files look like the followings.
**SBT Build**
```
-rw-r--r-- 1 dongjoon staff 87459461 Apr 1 19:01 spark-streaming-kinesis-asl-assembly-3.0.0-SNAPSHOT.jar
-rw-r--r-- 1 dongjoon staff 309 Apr 1 18:58 spark-streaming-kinesis-asl-assembly_2.12-3.0.0-SNAPSHOT-tests.jar
-rw-r--r-- 1 dongjoon staff 309 Apr 1 18:58 spark-streaming-kinesis-asl-assembly_2.12-3.0.0-SNAPSHOT.jar
```
**MAVEN Build**
```
-rw-r--r-- 1 dongjoon staff 8.6K Apr 1 18:55 spark-streaming-kinesis-asl-assembly_2.12-3.0.0-SNAPSHOT-sources.jar
-rw-r--r-- 1 dongjoon staff 8.6K Apr 1 18:55 spark-streaming-kinesis-asl-assembly_2.12-3.0.0-SNAPSHOT-test-sources.jar
-rw-r--r-- 1 dongjoon staff 8.7K Apr 1 18:55 spark-streaming-kinesis-asl-assembly_2.12-3.0.0-SNAPSHOT-tests.jar
-rw-r--r-- 1 dongjoon staff 21M Apr 1 18:55 spark-streaming-kinesis-asl-assembly_2.12-3.0.0-SNAPSHOT.jar
```
In addition, after SPARK-26856, the utility function `search_jar` is shared to find `avro` jar files which are identical for both `sbt` and `mvn`. To sum up, The current jar pattern parameter cannot handle both `kinesis` and `avro` jars. This PR splits the single pattern into two patterns.
## How was this patch tested?
Manual. Please note that this will remove only `Found multiple JARs` exception. Kinesis tests need more configurations to run locally.
```
$ build/sbt -Pkinesis-asl test:package streaming-kinesis-asl-assembly/assembly
$ export ENABLE_KINESIS_TESTS=1
$ python/run-tests.py --python-executables python2.7 --module pyspark-streaming
```
Closes#24268 from dongjoon-hyun/SPARK-26856.
Authored-by: Dongjoon Hyun <dhyun@apple.com>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>
## What changes were proposed in this pull request?
Avro is built-in but external data source module since Spark 2.4 but `from_avro` and `to_avro` APIs not yet supported in pyspark.
In this PR I've made them available from pyspark.
## How was this patch tested?
Please see the python API examples what I've added.
cd docs/
SKIP_SCALADOC=1 SKIP_RDOC=1 SKIP_SQLDOC=1 jekyll build
Manual webpage check.
Closes#23797 from gaborgsomogyi/SPARK-26856.
Authored-by: Gabor Somogyi <gabor.g.somogyi@gmail.com>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>
