[GitHub] [calcite] kasakrisz commented on a diff in pull request #2916: [CALCITE-5294] Improve PruneEmptyRules join instances to remove join if generates null and one branch is empty

[GitBox]

kasakrisz commented on code in PR #2916:
URL: https://github.com/apache/calcite/pull/2916#discussion_r977434703


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core/src/main/java/org/apache/calcite/rel/rules/PruneEmptyRules.java:
##########
@@ -551,17 +529,15 @@ public interface JoinRightEmptyRuleConfig extends 
PruneEmptyRule.Config {
             // "select * from emp left join dept" is not necessarily empty if
             // dept is empty
             // join can be removed and take the left branch, all columns come 
from dept are null
-            List<RexNode> projects = new ArrayList<>(
-                left.getRowType().getFieldCount() + 
empty.getRowType().getFieldCount());
-            List<String> columnNames = new ArrayList<>(
-                left.getRowType().getFieldCount() + 
empty.getRowType().getFieldCount());
-            // left
-            copyProjects(
-                rexBuilder, left.getRowType(), join.getRowType(), 0, projects, 
columnNames);
-            // right
-            addNullLiterals(rexBuilder, empty, projects, columnNames);
-
-            RelNode project = call.builder().push(left).project(projects, 
columnNames).build();
+            List<Pair<? extends RexNode, String>> projects =
+                Stream.concat(
+                    getProjectStream(left.getRowType(), join.getRowType(), 0, 
rexBuilder),
+                    getNullLiteralStream(empty, 
rexBuilder)).collect(Collectors.toList());
+
+            RelNode project = call.builder()
+                .push(left)
+                .project(Pair.left(projects), Pair.right(projects))
+                .build();

Review Comment:
   Adding the cast only in case of full outer join enabled replacing the 
`getProjectStream` method to a simpler `castToNullable` .
   I kept `Stream.concat()` otherwise converting from `stream` to `iterable` is 
required or if everything is `iterable` we loose the functional style in 
`castToNullable` and `getNullLiteralStream`



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