SERVER-43821 Make PlanStage and PlanExecutor return errors by throwing

This eliminates the need for the FAILURE status codes in
PlanStage and PlanExecutor, and brings query execution's
error reporting more in line with that of the rest of the
server. It also makes it easier for future implementations
of PlanExecutor to comply with the interface.

1 files changed, 17 insertions, 19 deletions

diff --git a/src/mongo/db/commands/dbcommands.cpp b/src/mongo/db/commands/dbcommands.cpp
index e543e543de3..8d9d6b9d9c7 100644
--- a/src/mongo/db/commands/dbcommands.cpp
+++ b/src/mongo/db/commands/dbcommands.cpp
@@ -542,30 +542,28 @@ public:
         long long size = 0;
         long long numObjects = 0;
 
-        RecordId loc;
-        BSONObj obj;
-        PlanExecutor::ExecState state;
-        while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, &loc))) {
-            if (estimate)
-                size += avgObjSize;
-            else
-                size += collection->getRecordStore()->dataFor(opCtx, loc).size();
-
-            numObjects++;
-
-            if ((maxSize && size > maxSize) || (maxObjects && numObjects > maxObjects)) {
-                result.appendBool("maxReached", true);
-                break;
+        try {
+            RecordId loc;
+            while (PlanExecutor::ADVANCED == exec->getNext(static_cast<BSONObj*>(nullptr), &loc)) {
+                if (estimate)
+                    size += avgObjSize;
+                else
+                    size += collection->getRecordStore()->dataFor(opCtx, loc).size();
+
+                numObjects++;
+
+                if ((maxSize && size > maxSize) || (maxObjects && numObjects > maxObjects)) {
+                    result.appendBool("maxReached", true);
+                    break;
+                }
             }
-        }
-
-        if (PlanExecutor::FAILURE == state) {
+        } catch (DBException& exception) {
             LOGV2_WARNING(23801,
                           "Internal error while reading {namespace}",
                           "Internal error while reading",
                           "namespace"_attr = ns);
-            uassertStatusOK(WorkingSetCommon::getMemberObjectStatus(obj).withContext(
-                "Executor error while reading during dataSize command"));
+            exception.addContext("Executor error while reading during dataSize command");
+            throw;
         }
 
         ostringstream os;