JingsongLi commented on a change in pull request #8781:
[FLINK-12874][table-common] Improve the semantics of zero length strings
URL: https://github.com/apache/flink/pull/8781#discussion_r295169573
##########
File path:
flink-table/flink-table-common/src/main/java/org/apache/flink/table/types/logical/BinaryType.java
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@@ -91,9 +92,11 @@ private BinaryType(int length, boolean isNullable) {
* For consistent behavior, the same logic applies to binary strings.
*
* <p>This method enables this special kind of binary string.
+ *
+ * <p>Zero-length binary strings have no serializable string
representation.
*/
public static BinaryType ofEmptyLiteral() {
- return new BinaryType(EMPTY_LITERAL_LENGTH, false);
+ return new BinaryType(EMPTY_LITERAL_LENGTH, true);
Review comment:
I prefer `ofEmptyLiteral(boolean isNullable)`.
Literal empty string will be empty literal non-nullable CharType.
But there are some nullable cases too.
Consider `substring('', 1, 3)`, I think we should return an empty literal
nullable VarCharType in blink runner, Unlike Flink runner, Blink runner tries
not to throw exceptions, which leads to task failure. Blink runner chooses
return null to when error in calculation. (be consistent with Hive and Spark)
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