Airblader commented on a change in pull request #17481:
URL: https://github.com/apache/flink/pull/17481#discussion_r728893668
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File path:
flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/functions/sql/FlinkSqlOperatorTable.java
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@@ -1145,6 +1145,16 @@ public boolean isDeterministic() {
public static final SqlFunction JSON_EXISTS =
SqlStdOperatorTable.JSON_EXISTS;
public static final SqlFunction JSON_VALUE =
SqlStdOperatorTable.JSON_VALUE;
public static final SqlFunction JSON_QUERY =
SqlStdOperatorTable.JSON_QUERY;
+ public static final SqlFunction JSON_STRING =
+ new SqlFunction(
+ "JSON_STRING",
+ SqlKind.OTHER_FUNCTION,
+ ReturnTypes.cascade(
+ ReturnTypes.explicit(SqlTypeName.VARCHAR),
+ SqlTypeTransforms.LEAST_NULLABLE),
Review comment:
Calcite's `TO_NULLABLE` actually has a (to me) surprising behavior that
breaks tests: for structured types – like `ROW` – it also checks the
nullability of all of the inner fields. This means that `ROW<r0 STRING> NOT
NULL` would be considered nullable. Big "wat?" moment to me, and curious to
have someone explain to me why that makes sense.
In any case, `LEAST_NULLABLE` does not have this behavior, and otherwise
does the same thing in our case here.
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