[FLINK-3634] [docs] Fix documentation for DataSetUtils.zipWithUniqueId() This closes #1817.
Project: http://git-wip-us.apache.org/repos/asf/flink/repo Commit: http://git-wip-us.apache.org/repos/asf/flink/commit/62e811fd Tree: http://git-wip-us.apache.org/repos/asf/flink/tree/62e811fd Diff: http://git-wip-us.apache.org/repos/asf/flink/diff/62e811fd Branch: refs/heads/release-1.0 Commit: 62e811fdbcd5f3f5049d96543269abcc8fc10a48 Parents: 1554c9b Author: Greg Hogan <c...@greghogan.com> Authored: Fri Mar 18 10:44:03 2016 -0400 Committer: Ufuk Celebi <u...@apache.org> Committed: Mon Apr 11 14:20:55 2016 +0200 ---------------------------------------------------------------------- docs/apis/batch/zip_elements_guide.md | 30 ++++++++++++++++-------------- 1 file changed, 16 insertions(+), 14 deletions(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/flink/blob/62e811fd/docs/apis/batch/zip_elements_guide.md ---------------------------------------------------------------------- diff --git a/docs/apis/batch/zip_elements_guide.md b/docs/apis/batch/zip_elements_guide.md index 8048f1c..59f723a 100644 --- a/docs/apis/batch/zip_elements_guide.md +++ b/docs/apis/batch/zip_elements_guide.md @@ -32,15 +32,17 @@ This document shows how {% gh_link /flink-java/src/main/java/org/apache/flink/ap {:toc} ### Zip with a Dense Index -For assigning consecutive labels to the elements, the `zipWithIndex` method should be called. It receives a data set as input and returns a new data set of unique id, initial value tuples. +`zipWithIndex` assigns consecutive labels to the elements, receiving a data set as input and returning a new data set of `(unique id, initial value)` 2-tuples. +This process requires two passes, first counting then labeling elements, and cannot be pipelined due to the synchronization of counts. +The alternative `zipWIthUniqueId` works in a pipelined fashion and is preferred when a unique labeling is sufficient. For example, the following code: <div class="codetabs" markdown="1"> <div data-lang="java" markdown="1"> {% highlight java %} ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment(); -env.setParallelism(1); -DataSet<String> in = env.fromElements("A", "B", "C", "D", "E", "F"); +env.setParallelism(2); +DataSet<String> in = env.fromElements("A", "B", "C", "D", "E", "F", "G", "H"); DataSet<Tuple2<Long, String>> result = DataSetUtils.zipWithIndex(in); @@ -54,8 +56,8 @@ env.execute(); import org.apache.flink.api.scala._ val env: ExecutionEnvironment = ExecutionEnvironment.getExecutionEnvironment -env.setParallelism(1) -val input: DataSet[String] = env.fromElements("A", "B", "C", "D", "E", "F") +env.setParallelism(2) +val input: DataSet[String] = env.fromElements("A", "B", "C", "D", "E", "F", "G", "H") val result: DataSet[(Long, String)] = input.zipWithIndex @@ -66,21 +68,21 @@ env.execute() </div> -will yield the tuples: (0,A), (1,B), (2,C), (3,D), (4,E), (5,F) +may yield the tuples: (0,G), (1,H), (2,A), (3,B), (4,C), (5,D), (6,E), (7,F) [Back to top](#top) -### Zip with an Unique Identifier -In many cases, one may not need to assign consecutive labels. -`zipWIthUniqueId` works in a pipelined fashion, speeding up the label assignment process. This method receives a data set as input and returns a new data set of unique id, initial value tuples. +### Zip with a Unique Identifier +In many cases one may not need to assign consecutive labels. +`zipWIthUniqueId` works in a pipelined fashion, speeding up the label assignment process. This method receives a data set as input and returns a new data set of `(unique id, initial value)` 2-tuples. For example, the following code: <div class="codetabs" markdown="1"> <div data-lang="java" markdown="1"> {% highlight java %} ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment(); -env.setParallelism(1); -DataSet<String> in = env.fromElements("A", "B", "C", "D", "E", "F"); +env.setParallelism(2); +DataSet<String> in = env.fromElements("A", "B", "C", "D", "E", "F", "G", "H"); DataSet<Tuple2<Long, String>> result = DataSetUtils.zipWithUniqueId(in); @@ -94,8 +96,8 @@ env.execute(); import org.apache.flink.api.scala._ val env: ExecutionEnvironment = ExecutionEnvironment.getExecutionEnvironment -env.setParallelism(1) -val input: DataSet[String] = env.fromElements("A", "B", "C", "D", "E", "F") +env.setParallelism(2) +val input: DataSet[String] = env.fromElements("A", "B", "C", "D", "E", "F", "G", "H") val result: DataSet[(Long, String)] = input.zipWithUniqueId @@ -106,6 +108,6 @@ env.execute() </div> -will yield the tuples: (0,A), (2,B), (4,C), (6,D), (8,E), (10,F) +may yield the tuples: (0,G), (1,A), (2,H), (3,B), (5,C), (7,D), (9,E), (11,F) [Back to top](#top)
