Addressed comments 2

docs/dev/table/streaming/match_recognize.md

@@ -211,13 +211,13 @@ If a condition is not defined for a pattern variable, a default condition will b
 
 For a more detailed explanation about expressions that can be used in those clauses, please have a look at the [event stream navigation](#pattern-navigation) section.
 
-### Scalar & Aggregate functions
+### Aggregations
 
-One can use scalar and aggregate functions in those clauses, both [built-in]({{ site.baseurl }}/dev/table/sql.html#built-in-functions) as well as provide [user defined]({{ site.baseurl }}/dev/table/udfs.html) functions.
+Aggregations can be used in `DEFINE` and `MEASURES` clauses. Both [built-in]({{ site.baseurl }}/dev/table/sql.html#built-in-functions) and custom [user defined]({{ site.baseurl }}/dev/table/udfs.html) functions are supported.
 
-Aggregate functions are applied to subset of rows mapped to a match. To understand how those subsets are evaluated have a look at the [event stream navigation](#pattern-navigation) section.
+Aggregate functions are applied to each subset of rows mapped to a match. In order to understand how those subsets are evaluated have a look at the [event stream navigation](#pattern-navigation) section.
 
-With a task to find the longest period of time for which the average price of a ticker did not go below certain threshold, one can see how expressible `MATCH_RECOGNIZE` can become with aggregations.
+The task of the following example is to find the longest period of time for which the average price of a ticker did not go below certain threshold. It shows how expressible `MATCH_RECOGNIZE` can become with aggregations.
 This task can be performed with the following query:
 
 {% highlight sql %}
@@ -256,8 +256,8 @@ symbol         rowtime         price    tax
 'ACME'  '01-Apr-11 10:00:10'   30      1
 {% endhighlight %}
 
-The query will accumulate events as part of `A` pattern variable as long as the average price of them does not exceed 15. Which will happen at `01-Apr-11 10:00:04`. The next such period that starts then will
-exceed average price of 15 at `01-Apr-11 10:00:10`. Thus the results for said query will be:
+The query will accumulate events as part of the pattern variable `A` as long as the average price of them does not exceed `15`. For example, such a limit exceeding happens at `01-Apr-11 10:00:04`.
+The following period exceeds the average price of `15` again at `01-Apr-11 10:00:10`. Thus the results for said query will be:
 
 {% highlight text %}
  symbol       start_tstamp       end_tstamp          avgPrice
@@ -266,6 +266,8 @@ ACME       01-APR-11 10:00:00  01-APR-11 10:00:03     14.5
 ACME       01-APR-11 10:00:04  01-APR-11 10:00:09     13.5
 {% endhighlight %}
 
+<span class="label label-info">Note</span> Aggregations can be applied to expressions, but only if they reference a single pattern variable. Thus `SUM(A.price * A.tax)` is a valid one, but `AVG(A.price * B.tax)` is not.
+
 An important thing to have in mind is how aggregates behave in situation when no rows where mapped to certain pattern variable. Every aggregate, beside `COUNT` will produce `null` in those cases. `COUNT` on the other hand will
 produce 0.
 

flink-libraries/flink-table/src/main/java/org/apache/calcite/sql/validate/SqlValidatorImpl.java

@@ -136,6 +136,7 @@
 
 /*
  * THIS FILE HAS BEEN COPIED FROM THE APACHE CALCITE PROJECT UNTIL CALCITE-2707 IS FIXED.
+ * (Added lines: 5937-5943)
  */
 
 /**
@@ -5934,11 +5935,13 @@ private static class NavigationExpander extends NavigationModifier {
 			List<SqlNode> operands = call.getOperandList();
 			List<SqlNode> newOperands = new ArrayList<>();
 
+			// This code is a workaround for CALCITE-2707
 			if (call.getFunctionQuantifier() != null
 				&& call.getFunctionQuantifier().getValue() == SqlSelectKeyword.DISTINCT) {
 				final SqlParserPos pos = call.getParserPosition();
 				throw SqlUtil.newContextException(pos, Static.RESOURCE.functionQuantifierNotAllowed(call.toString()));
 			}
+			// This code is a workaround for CALCITE-2707
 
 			if (isLogicalNavigation(kind) || isPhysicalNavigation(kind)) {
 				SqlNode inner = operands.get(0);