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https://issues.apache.org/jira/browse/HADOOP-6420?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aaron Kimball updated HADOOP-6420:
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Attachment: HADOOP-6420.8.patch
I realized after working more on MAPREDUCE-1126 that I need the ability to
determine if a map is empty or not; when I was using the HashMap-based
(deep-copy) getMap(), this was accomplished via {{Map.size() == 0}}; but
determining the map's size in general requires iteration, which we decided not
to support due to the expense.
Instead I've added a sentinel value that indicates whether the map exists or
not. This is set by {{setMap()}} and can be read with {{mapExists()}}. Since we
also support users creating maps using the underlying properties (e.g.,
{{conf.set("foo.bar", "a"); conf.set("foo.baz", "b"); conf.getMap("foo")}}),
I've added a {{declareMap()}} method that adds the sentinel as well. (so you
could write: {{conf.set("foo.bar", "a"); conf.set("foo.baz", "b");
conf.declareMap("foo"); assertTrue(conf.mapExists("foo")}}). This works by
creating a key named {{"foo"}} in the Configuration whose value is {{"$MAP$"}}.
This is necessary in MAPREDUCE-1126 to determine whether the user has properly
called a metadata-API {{setMapOutputKeyClass() / setMapOutputKeySchema()}}
method, or whether we should fall back to the deprecated
{{JobConf.getMapOutputKeyClass() / JobConf.getOutputKeyClass()}} API.
> String-to-String Maps should be embeddable in Configuration
> -----------------------------------------------------------
>
> Key: HADOOP-6420
> URL: https://issues.apache.org/jira/browse/HADOOP-6420
> Project: Hadoop Common
> Issue Type: Improvement
> Components: conf
> Reporter: Aaron Kimball
> Assignee: Aaron Kimball
> Attachments: HADOOP-6420.2.patch, HADOOP-6420.3.patch,
> HADOOP-6420.4.patch, HADOOP-6420.5.patch, HADOOP-6420.6.patch,
> HADOOP-6420.7.patch, HADOOP-6420.8.patch, HADOOP-6420.patch
>
>
> Per MAPREDUCE-1126, we need to be able to take a map of (key, value) pairs
> and embed that inside a Configuration object.
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