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Posted to github@beam.apache.org by GitBox <gi...@apache.org> on 2020/10/19 22:18:18 UTC
[GitHub] [beam] ibzib commented on a change in pull request #12963: [BEAM-10983] Add getting started from Spark page
ibzib commented on a change in pull request #12963:
URL: https://github.com/apache/beam/pull/12963#discussion_r508095053
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File path: website/www/site/content/en/get-started/from-spark.md
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@@ -0,0 +1,245 @@
+---
+title: "Getting started from Apache Spark"
+---
+<!--
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+# Getting started from Apache Spark
+
+{{< localstorage language language-py >}}
+
+If you already know [_Apache Spark_](http://spark.apache.org/),
+learning _Apache Beam_ is easy.
+Beam and Spark are mostly equivalent, so you already know the basic concepts.
+
+A collection of elements in Spark is called a _Resilient Distributed Dataset_ (RDD),
+while in Beam it's called a _Parallel Collection_ (PCollection).
+A PCollection in Beam does _not_ have any ordering guarantees.
+
+Likewise, a transform in Beam is called a _Parallel Transform_ (PTransform).
+
+Here are some examples of common operations and their equivalent between PySpark and Beam.
+
+## Overview
+
+Here's a simple example of a PySpark pipeline that takes the numbers from one to four,
+multiplies them by two, adds all the values together, and prints the result.
+
+{{< highlight py >}}
+import pyspark
+
+with pyspark.SparkContext() as sc:
+ result = (
+ sc.parallelize([1, 2, 3, 4])
+ .map(lambda x: x * 2)
+ .reduce(lambda x, y: x + y)
+ )
+ print(result)
+{{< /highlight >}}
+
+In Beam you _pipe_ your data through the pipeline using the
+_pipe operator_ `|` like `data | beam.Map(...)` instead of chaining
+methods like `data.map(...)`, but they're doing the same thing.
+
+Here's how an equivalent pipeline looks like in Beam.
+
+{{< highlight py >}}
+import apache_beam as beam
+
+with beam.Pipeline() as pipeline:
+ result = (
+ pipeline
+ | beam.Create([1, 2, 3, 4])
+ | beam.Map(lambda x: x * 2)
+ | beam.CombineGlobally(sum)
+ | beam.Map(print)
+ )
+{{< /highlight >}}
+
+> ℹ️ Note that we called `print` inside a `Map` transform.
+> That's because we can only access the elements of a PCollection
+> from within a PTransform.
+
+A label can optionally be added to a transform using the
+_right shift operator_ `>>` like `data | 'My description' >> beam.Map(...)`.
+This serves both as comments and makes your pipeline easier to debug.
+
+This is how the pipeline looks after adding labels.
+
+{{< highlight py >}}
+import apache_beam as beam
+
+with beam.Pipeline() as pipeline:
+ result = (
+ pipeline
+ | 'Create numbers' >> beam.Create([1, 2, 3, 4])
+ | 'Multiply by two' >> beam.Map(lambda x: x * 2)
+ | 'Sum everything' >> beam.CombineGlobally(sum)
+ | beam.Map(print)
+ )
+{{< /highlight >}}
+
+## Setup
+
+Here's a comparison on how to get started both in PySpark and Beam.
+
+{{< table >}}
+<table>
+<tr>
+ <th></th>
+ <th>PySpark</th>
+ <th>Beam</th>
+</tr>
+<tr>
+ <td><b>Install</b></td>
+ <td><code>$ pip install pyspark</code></td>
+ <td><code>$ pip install apache-beam</code></td>
+</tr>
+<tr>
+ <td><b>Imports</b></td>
+ <td><code>import pyspark</code></td>
+ <td><code>import apache_beam as beam</code></td>
+</tr>
+<tr>
+ <td><b>Creating a<br>local pipeline</b></td>
+ <td>
+ <code>with pyspark.SparkContext() as sc:</code><br>
+ <code> # Your pipeline code here.</code>
+ </td>
+ <td>
+ <code>with beam.Pipeline() as pipeline:</code><br>
+ <code> # Your pipeline code here.</code>
+ </td>
+</tr>
+<tr>
+ <td><b>Creating values</b></td>
+ <td><code>values = sc.parallelize([1, 2, 3, 4])</code></td>
+ <td><code>values = pipeline | beam.Create([1, 2, 3, 4])</code></td>
+</tr>
+<tr>
+ <td><b>Creating<br>key-value pairs</b></td>
+ <td>
+ <code>pairs = sc.parallelize([</code><br>
+ <code> ('key1', 'value1'),</code><br>
+ <code> ('key2', 'value2'),</code><br>
+ <code> ('key3', 'value3'),</code><br>
+ <code>])</code>
+ </td>
+ <td>
+ <code>pairs = pipeline | beam.Create([</code><br>
+ <code> ('key1', 'value1'),</code><br>
Review comment:
> I don't have an @apache.org email so I can't open the discussion.
Anyone should be able to join the ASF slack. There is an invite link on the Beam website: https://beam.apache.org/community/contact-us/
The case I linked might be an isolated bug. If tuples have worked for you, I'm fine with keeping them in the documentation.
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File path: website/www/site/content/en/get-started/from-spark.md
##########
@@ -71,6 +71,17 @@ with beam.Pipeline() as pipeline:
> That's because we can only access the elements of a PCollection
> from within a PTransform.
+Another thing to note is that Beam pipelines are constructed _lazily_.
+This means that when you _pipe_ `|` data you're only _decalring_ the
Review comment:
```suggestion
This means that when you _pipe_ `|` data you're only _declaring_ the
```
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