Always output left side join key for inner join

Author: feilong-liu

presto-main-base/src/main/java/com/facebook/presto/sql/planner/optimizations/UnaliasSymbolReferences.java

@@ -591,18 +591,26 @@ public PlanNode visitJoin(JoinNode node, RewriteContext<Void> context)
             if (node.getType().equals(INNER)) {
                 canonicalCriteria.stream()
                         .filter(clause -> clause.getLeft().getType().equals(clause.getRight().getType()) && clause.getLeft().getType().equalValuesAreIdentical())
-                        .filter(clause -> node.getOutputVariables().contains(clause.getLeft()))
+                        .filter(clause -> node.getOutputVariables().contains(clause.getRight()))
                         .forEach(clause -> map(clause.getRight(), clause.getLeft()));
             }
 
+            List<VariableReferenceExpression> canonicalizedOutput = canonicalizeAndDistinct(node.getOutputVariables());
+            if (canonicalCriteria.stream().map(x -> x.getRight().getName()).anyMatch(mapping::containsKey)) {
+                canonicalizedOutput = ImmutableList.<VariableReferenceExpression>builder()
+                        .addAll(canonicalizedOutput.stream().filter(left.getOutputVariables()::contains).collect(Collectors.toList()))
+                        .addAll(canonicalizedOutput.stream().filter(right.getOutputVariables()::contains).collect(Collectors.toList()))
+                        .build();
+            }
+
             return new JoinNode(
                     node.getSourceLocation(),
                     node.getId(),
                     node.getType(),
                     left,
                     right,
                     canonicalCriteria,
-                    canonicalizeAndDistinct(node.getOutputVariables()),
+                    canonicalizedOutput,
                     canonicalFilter,
                     canonicalLeftHashVariable,
                     canonicalRightHashVariable,