DEVEXP-477 Upgraded to Java Client 6.2.1

Can't believe it, but resultDoc with JacksonHandle is consistently outperforming resultRows with a StringHandle. So not changing that code, just changed the comments.

Author: rjrudin

build.gradle

@@ -20,7 +20,7 @@ repositories {
 
 dependencies {
   compileOnly 'org.apache.spark:spark-sql_2.12:3.4.0'
-  implementation "com.marklogic:marklogic-client-api:6.2.0"
+  implementation "com.marklogic:marklogic-client-api:6.2.1"
 
   // Makes it possible to use lambdas in Java 8 to implement Spark's Function1 and Function2 interfaces
   // See https://github.com/scala/scala-java8-compat for more information

src/main/java/com/marklogic/spark/reader/ReadContext.java

@@ -120,9 +120,9 @@ Iterator<JsonNode> readRowsInBucket(RowManager rowManager, PlanAnalysis.Partitio
         PlanBuilder.Plan plan = buildPlanForBucket(rowManager, bucket);
         JacksonHandle jsonHandle = new JacksonHandle();
         jsonHandle.setPointInTimeQueryTimestamp(serverTimestamp);
-        // Unable to use resultRows as Java Client <= 6.2.0 has a bug where the serverTimestamp is ignored.
-        // TODO Change this to use resultRows once Java Client 6.2.1 is available. That should perform better as it
-        // avoids creating a JsonNode.
+        // Remarkably, the use of resultDoc has consistently proven to be a few percentage points faster than using
+        // resultRows with a StringHandle, even though the latter avoids the need for converting to and from a JsonNode.
+        // The overhead with resultRows may be due to the processing of a multipart response; it's not yet clear.
         JsonNode result = rowManager.resultDoc(plan, jsonHandle).get();
         return result != null && result.has("rows") ?
             result.get("rows").iterator() :