[FLINK-13811][python] Support converting flink Table to pandas DataFrame #12148

dianfu · 2020-05-14T09:34:03Z

What is the purpose of the change

This pull request add support to convert flink Table to pandas DataFrame

Brief change log

Add utility ArrowUtils.collectAsPandasDataFrame to materialize the results of the table and serialize them into arrow format
Add Table.to_pandas in PyFlink to convert flink Table to pandas DataFrame

Verifying this change

This change added tests and can be verified as follows:

Added tests test_pandas_conversion.test_to_pandas and test_pandas_conversion.test_empty_to_pandas

Does this pull request potentially affect one of the following parts:

Dependencies (does it add or upgrade a dependency): (no)
The public API, i.e., is any changed class annotated with @Public(Evolving): (no)
The serializers: (no)
The runtime per-record code paths (performance sensitive): (no)
Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: (no)
The S3 file system connector: (no)

Documentation

Does this pull request introduce a new feature? (yes)
If yes, how is the feature documented? (docs)

flinkbot · 2020-05-14T09:46:03Z

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zjffdu · 2020-05-14T09:54:06Z

@dianfu Is arrow a dependency of pyflink ? I mean whether arrow will be installed when running pip install apache_flink

dianfu · 2020-05-14T09:55:22Z

Yes, it will be installed when running pip install apache_flink

flinkbot · 2020-05-14T09:59:33Z

CI report:

65d1588 Azure: FAILURE

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WeiZhong94

@dianfu Thanks for your PR! Looks good overall, just some minor comments.

WeiZhong94 · 2020-05-14T12:21:49Z

docs/dev/table/python/conversion_of_pandas.md

+
+## Convert PyFlink Table to Pandas DataFrame
+
+It also supports to convert a PyFlink Table to a Pandas DataFrame. Internally, it will materialize the results of the 


supports to convert -> supports converting?

WeiZhong94 · 2020-05-14T12:26:14Z

docs/dev/table/python/conversion_of_pandas.md

+## Convert PyFlink Table to Pandas DataFrame
+
+It also supports to convert a PyFlink Table to a Pandas DataFrame. Internally, it will materialize the results of the 
+table and serialize them into multiple arrow batches of Arrow columnar format at client side. The maximum arrow batch size


arrow -> Arrow?

WeiZhong94 · 2020-05-14T12:28:24Z

flink-python/pyflink/table/serializers.py

+
+    def load_from_iterator(self, itor):
+        class IteratorIO(io.RawIOBase):
+            def __init__(self, itor):


add super().init() method?

WeiZhong94 · 2020-05-14T12:29:29Z

flink-python/src/main/java/org/apache/flink/table/runtime/arrow/ArrowUtils.java

+
+	private static boolean isBlinkPlanner(Table table) {
+		TableEnvironment tableEnv = ((TableImpl) table).getTableEnvironment();
+		if (tableEnv instanceof BatchTableEnvironment || tableEnv instanceof TableEnvImpl) {


The tableEnv instanceof BatchTableEnvironment is unnecessary.

WeiZhong94 · 2020-05-14T12:31:07Z

flink-python/src/main/java/org/apache/flink/table/runtime/arrow/ArrowUtils.java

+					// The SelectTableSink of blink planner will convert the table schema and we
+					// need to keep the table schema used here be consistent with the converted table schema
+					TableSchema convertedTableSchema = SelectTableSinkSchemaConverter.changeDefaultConversionClass(table.getSchema());
+					DataFormatConverters.DataFormatConverter converter = DataFormatConverters.getConverterForDataType(convertedTableSchema.toRowDataType());


Break this line as it is too long?

WeiZhong94 · 2020-05-14T12:31:48Z

flink-python/pyflink/table/tests/test_pandas_conversion.py

+    def test_to_pandas(self):
+        table = self.t_env.from_pandas(self.pdf, self.data_type)
+        result_pdf = table.to_pandas()
+        self.assertTrue(2, len(result_pdf))


assertEqual?

dianfu · 2020-05-15T01:47:12Z

@WeiZhong94 Thanks for the review. The test failures are instable cases of Kafka which are not related to this PR. Merging...

[FLINK-13811][python] Support converting flink Table to pandas DataFrame

634970c

rmetzger added the review=description? label May 14, 2020

rmetzger added the component=API/Python label May 14, 2020

WeiZhong94 reviewed May 14, 2020

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WeiZhong94 approved these changes May 14, 2020

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address review

65d1588

dianfu closed this in d417889 May 15, 2020

dianfu deleted the FLINK-13811 branch June 10, 2020 03:05

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[FLINK-13811][python] Support converting flink Table to pandas DataFrame #12148

[FLINK-13811][python] Support converting flink Table to pandas DataFrame #12148

dianfu commented May 14, 2020

flinkbot commented May 14, 2020

zjffdu commented May 14, 2020

dianfu commented May 14, 2020

flinkbot commented May 14, 2020 •

edited

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WeiZhong94 May 14, 2020

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WeiZhong94 May 14, 2020

dianfu commented May 15, 2020


		## Convert PyFlink Table to Pandas DataFrame

		It also supports to convert a PyFlink Table to a Pandas DataFrame. Internally, it will materialize the results of the

[FLINK-13811][python] Support converting flink Table to pandas DataFrame #12148

[FLINK-13811][python] Support converting flink Table to pandas DataFrame #12148

Conversation

dianfu commented May 14, 2020

What is the purpose of the change

Brief change log

Verifying this change

Does this pull request potentially affect one of the following parts:

Documentation

flinkbot commented May 14, 2020

Automated Checks

Review Progress

zjffdu commented May 14, 2020

dianfu commented May 14, 2020

flinkbot commented May 14, 2020 • edited

CI report:

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dianfu commented May 15, 2020

flinkbot commented May 14, 2020 •

edited