[ASTERIXDB-2377][OTH] Fix JSON of Additional Expressions

- user model changes: no
- storage format changes: no
- interface changes: no

Details:
- Fix JSON of additional expressions in the JSON
  plan printer of InsertDeleteUpsertOperator.

Change-Id: I2d13b91b4e5e36b156f52fbb09f0ddcffe1deda3
Reviewed-on: https://asterix-gerrit.ics.uci.edu/2627
Sonar-Qube: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Contrib: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Till Westmann <tillw@apache.org>
diff --git a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitorJson.java b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitorJson.java
index 1076eb5..8acf08b 100644
--- a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitorJson.java
+++ b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/prettyprint/LogicalOperatorPrettyPrintVisitorJson.java
@@ -544,9 +544,9 @@
         addIndent(indent).append("\"from-record\": \"")
                 .append(op.getPayloadExpression().getValue().accept(exprVisitor, indent) + "\"");
         if (op.getAdditionalNonFilteringExpressions() != null) {
-            buffer.append(",\n\"meta\": \"");
+            buffer.append(",\n\"meta\": {");
             pprintExprList(op.getAdditionalNonFilteringExpressions(), 0);
-            buffer.append("\"");
+            buffer.append("}");
         }
         buffer.append(",\n");
         addIndent(indent).append("\"partitioned-by\": {");