sunjincheng121 commented on a change in pull request #7167: [FLINK-10973]
[table] Add support for map to table API
URL: https://github.com/apache/flink/pull/7167#discussion_r236108631
##########
File path:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/table.scala
##########
@@ -999,6 +999,93 @@ class Table(
new OverWindowedTable(this, overWindows.toArray)
}
+ /**
+ * Performs a map operation with an user-defined function. The output will
be flattened
+ * if the output type is composite type.
+ *
+ * Scala Example:
+ * {{{
+ * class MyMapFunction extends ScalarFunction {
+ * def eval(str: String): Row = {
+ * Row.of(str, str)
+ * }
+ *
+ * def getResultType(signature: Array[Class[_]]): TypeInformation[_] =
+ * Types.ROW(Types.STRING, Types.STRING)
+ * }
+ *
+ * val func = new MyMapFunction()
+ * table.map(func('c))
+ * }}}
+ *
+ * Java Example:
+ * {{{
+ * class MyMapFunction extends ScalarFunction {
+ * public Row eval(String str) {
+ * return Row.of(str, str);
+ * }
+ *
+ * public TypeInformation getResultType(Class[] signature) {
+ * return new RowTypeInfo(BasicTypeInfo.STRING_TYPE_INFO,
BasicTypeInfo.STRING_TYPE_INFO);
+ * }
+ * }
+ *
+ * ScalarFunction func = new MyMapFunction();
+ * tableEnv.registerFunction("func", func);
+ * table.map("func(c)");
+ * }}}
+ */
+ def map(mapFunction: Expression): Table = {
+ mapFunction match {
+ case _: ScalarFunctionCall =>
+ case _ => throw new ValidationException("Only ScalarFunction can be used
in map.")
+ }
+
+ val expandedFields = expandProjectList(Seq(Flattening(mapFunction)),
logicalPlan, tableEnv)
Review comment:
Here you use flatten to implement map, map needs to guarantee
non-deterministic and deterministic user-defined scalar function works well,
otherwise the reason must be explained,What do you think?
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