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commit c8413e3afc7ea65c6e9c8baf01557dc15b6e7089
Author: Mergebot <merge...@apache.org>
AuthorDate: Thu Feb 22 10:53:44 2018 -0800
Prepare repository for deployment.
---
content/documentation/sdks/python-type-safety/index.html | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/content/documentation/sdks/python-type-safety/index.html
b/content/documentation/sdks/python-type-safety/index.html
index e116b24..1f3ef16 100644
--- a/content/documentation/sdks/python-type-safety/index.html
+++ b/content/documentation/sdks/python-type-safety/index.html
@@ -281,19 +281,21 @@ words_with_lens = words | MyTransform()
<p>In addition to using type hints for type checking at pipeline construction,
you can enable runtime type checking to check that actual elements satisfy the
declared type constraints during pipeline execution.</p>
-<p>For example, the following code would pass at both pipeline construction
and runtime.</p>
+<p>For example, the following pipeline emits elements of the wrong type.
Depending on the runner implementation, its execution may or may not fail at
runtime.</p>
<div class="highlighter-rouge"><pre class="highlight"><code>p |
beam.Create(['a']) | beam.Map(lambda x: 3).with_output_types(str)
</code></pre>
</div>
-<p>However, if you enable runtime type checking, the code passes at pipeline
construction and fails at runtime. To enable runtime type checking, set the
pipeline option <code class="highlighter-rouge">runtime_type_check</code> to
<code class="highlighter-rouge">True</code>.</p>
+<p>However, if you enable runtime type checking, the code is guaranteed to
fail at runtime. To enable runtime type checking, set the pipeline option <code
class="highlighter-rouge">runtime_type_check</code> to <code
class="highlighter-rouge">True</code>.</p>
<div class="highlighter-rouge"><pre class="highlight"><code>p |
beam.Create(['a']) | beam.Map(lambda x: 3).with_output_types(str)
p.run()
</code></pre>
</div>
+<p>Note that because runtime type checks are done for each <code
class="highlighter-rouge">PCollection</code> element, enabling this feature may
incur a significant performance penalty. It is therefore recommended that
runtime type checks are disabled for production pipelines.</p>
+
<h2 id="use-of-type-hints-in-coders">Use of Type Hints in Coders</h2>
<p>When your pipeline reads, writes, or otherwise materializes its data, the
elements in your <code class="highlighter-rouge">PCollection</code> need to be
encoded and decoded to and from byte strings. Byte strings are used for
intermediate storage, for comparing keys in <code
class="highlighter-rouge">GroupByKey</code> operations, and for reading from
sources and writing to sinks.</p>
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