[flink] 02/06: [hotfix][table-common] Add assumption about expressions and data types

[tw...@apache.org]

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twalthr pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/flink.git

commit 1ec14eb44db7b6ea28f560eb69c6d016890bdb70
Author: Timo Walther <tw...@apache.org>
AuthorDate: Tue May 21 12:23:20 2019 +0200

    [hotfix][table-common] Add assumption about expressions and data types
---
 .../main/java/org/apache/flink/table/expressions/Expression.java    | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/flink-table/flink-table-common/src/main/java/org/apache/flink/table/expressions/Expression.java b/flink-table/flink-table-common/src/main/java/org/apache/flink/table/expressions/Expression.java
index 6b68dce..57c73d4 100644
--- a/flink-table/flink-table-common/src/main/java/org/apache/flink/table/expressions/Expression.java
+++ b/flink-table/flink-table-common/src/main/java/org/apache/flink/table/expressions/Expression.java
@@ -19,6 +19,7 @@
 package org.apache.flink.table.expressions;
 
 import org.apache.flink.annotation.PublicEvolving;
+import org.apache.flink.table.types.DataType;
 
 import java.util.List;
 
@@ -26,8 +27,11 @@ import java.util.List;
  * The interface for all expressions.
  *
  * <p>Expressions represent a logical tree for producing a computation result. Every expression
- * consists of zero or more sub-expressions. Expressions might be literal values, function calls,
+ * consists of zero, one, or more sub-expressions. Expressions might be literal values, function calls,
  * or field references.
+ *
+ * <p>Expressions are part of the API. Thus, values and return types are expressed as instances of
+ * {@link DataType}.
  */
 @PublicEvolving
 public interface Expression {