twalthr commented on code in PR #26331:
URL: https://github.com/apache/flink/pull/26331#discussion_r2007636419
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flink-table/flink-table-api-java/src/main/java/org/apache/flink/table/api/Expressions.java:
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@@ -131,17 +134,28 @@ public static ApiExpression lit(Object v) {
}
/**
- * Creates a SQL literal of a given {@link DataType}.
+ * Creates a literal (i.e. a constant value) of a given {@link DataType}.
*
* <p>The method {@link #lit(Object)} is preferred as it extracts the
{@link DataType}
* automatically. Use this method only when necessary. The class of {@code
v} must be supported
- * according to the {@link
- *
org.apache.flink.table.types.logical.LogicalType#supportsInputConversion(Class)}.
+ * according to the {@link LogicalType#supportsInputConversion(Class)}.
*/
public static ApiExpression lit(Object v, DataType dataType) {
return new ApiExpression(valueLiteral(v, dataType));
}
+ /**
+ * Creates a literal describing an arbitrary, unvalidated list of column
names.
+ *
+ * <p>Passing a list of columns can be useful for parameterizing a
function. In particular, it
+ * enables declaring the {@code on_time} argument for {@link
ProcessTableFunction}.
+ *
+ * <p>The data type will be {@link DataTypes#DESCRIPTOR()}.
+ */
+ public static ApiExpression descriptor(String... columnNames) {
Review Comment:
Calcite doesn't support them yet. We would need to update Calcite's
DescriptorSqlOperator and the parser. But this is future work.
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