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ASF GitHub Bot commented on FLINK-3042: --------------------------------------- Github user greghogan commented on a diff in the pull request: https://github.com/apache/flink/pull/2337#discussion_r77714875 --- Diff: flink-core/src/main/java/org/apache/flink/api/common/typeinfo/TypeInformation.java --- @@ -122,14 +123,25 @@ public abstract Class<T> getTypeClass(); /** - * Returns the generic parameters of this type. + * Optional method for giving Flink's type extraction system information about the mapping + * of a generic type parameter to the type information of a subtype. This information is necessary + * in cases where type information should be deduced from an input type. * - * @return The list of generic parameters. This list can be empty. + * For instance, a method for a {@link Tuple2} would look like this: + * <code> + * Map m = new HashMap(); + * m.put("T0", this.getTypeAt(0)); + * m.put("T1", this.getTypeAt(1)); + * return m; + * </code> + * + * @return map of inferred subtypes; it must not contain all generic parameters as key; --- End diff -- What is meant by "it must not contain all generic parameters as key"? > Define a way to let types create their own TypeInformation > ---------------------------------------------------------- > > Key: FLINK-3042 > URL: https://issues.apache.org/jira/browse/FLINK-3042 > Project: Flink > Issue Type: Improvement > Components: Core > Affects Versions: 0.10.0 > Reporter: Stephan Ewen > Assignee: Timo Walther > Fix For: 1.0.0 > > > Currently, introducing new Types that should have specific TypeInformation > requires > - Either integration with the TypeExtractor > - Or manually constructing the TypeInformation (potentially at every place) > and using type hints everywhere. > I propose to add a way to allow classes to create their own TypeInformation > (like a static method "createTypeInfo()"). > To support generic nested types (like Optional / Either), the type extractor > would provide a Map of what generic variables map to what types (deduced from > the input). The class can use that to create the correct nested > TypeInformation (possibly by calling the TypeExtractor again, passing the Map > of generic bindings). -- This message was sent by Atlassian JIRA (v6.3.4#6332)