Tweak Operator Name Query to avoid op application

source/adios2/core/Engine.h

@@ -529,6 +529,10 @@ class Engine
     void RegisterCreatedVariable(const VariableBase *var);
     void RemoveCreatedVars();
 
+    /** true: We only need the name of an operator used in Get, not actual operation
+     */
+    bool m_OperatorNameQuery = false;
+
 protected:
     /** from ADIOS class passed to Engine created with Open
      *  if no communicator is passed */

source/adios2/core/VariableBase.cpp

@@ -346,12 +346,9 @@ size_t VariableBase::AddOperation(const std::string &type, const Params &paramet
         if (!m_Operations.empty() && (m_Operations[0]->m_TypeString == "null"))
         {
             // if there's a dummy operation in place, replace it
-            m_Operations[0] = op;
-        }
-        else
-        {
-            m_Operations.push_back(op);
+            m_Operations.clear();
         }
+        m_Operations.push_back(op);
     }
     else
     {

source/adios2/operator/plugin/PluginOperator.cpp

@@ -94,6 +94,14 @@ void PluginOperator::PluginInit(const std::string &pluginName, const std::string
     // add for external visibility
     m_PluginName = pluginName;
     m_PluginLibrary = pluginLibrary;
+    if (m_OperatorNameQuery)
+    {
+        auto m = MakeMessage("Plugins", "PluginOperator", "PluginInit",
+                             "Succeeding in load library " + m_PluginLibrary +
+                                 " looking for plugin " + m_PluginName,
+                             -1, helper::LogMode::EXCEPTION);
+        throw PluginLoadFailure(m, pluginLibrary, pluginName);
+    }
 }
 
 size_t PluginOperator::GetEstimatedSize(const size_t ElemCount, const size_t ElemSize,

source/adios2/operator/plugin/PluginOperator.h

@@ -50,6 +50,7 @@ class PluginOperator : public core::Operator
 
     std::string m_PluginLibrary;
     std::string m_PluginName;
+    bool m_OperatorNameQuery = false;
 
 protected:
     void PluginInit(const std::string &pluginName, const std::string &pluginLibrary);

source/adios2/toolkit/format/bp5/BP5Deserializer.cpp

@@ -31,6 +31,7 @@
 #endif
 
 #include "adios2/operator/OperatorFactory.h"
+#include "adios2/operator/plugin/PluginOperator.h"
 
 #include <array>
 #include <float.h>
@@ -1993,22 +1994,39 @@ void BP5Deserializer::FinalizeGet(const ReadRequest &Read, const bool freeAddr)
             std::shared_ptr<Operator> op = nullptr;
             VariableBase *VB =
                 static_cast<VariableBase *>(((struct BP5VarRec *)Req.VarRec)->Variable);
-            if (!VB->m_Operations.empty() && (VB->m_Operations[0]->m_TypeString != "null"))
-            {
-                op = VB->m_Operations[0];
-            }
-            else
-            {
-                Operator::OperatorType compressorType =
-                    static_cast<Operator::OperatorType>(IncomingData[0]);
-                op = MakeOperator(OperatorTypeToString(compressorType), {});
-                VB->m_Operations.resize(1);
-                VB->m_Operations[0] = op;
-            }
-            op->SetAccuracy(VB->GetAccuracyRequested());
-
             {
                 std::lock_guard<std::mutex> lockGuard(mutexDecompress);
+                // lock_guard protects mods to VB->m_Operations as well as the decompress operator
+                if (!VB->m_Operations.empty() && (VB->m_Operations[0]->m_TypeString != "null"))
+                {
+                    op = VB->m_Operations[0];
+                }
+                else
+                {
+                    Operator::OperatorType compressorType =
+                        static_cast<Operator::OperatorType>(IncomingData[0]);
+                    op = MakeOperator(OperatorTypeToString(compressorType), {});
+                    VB->m_Operations.clear();
+                    VB->m_Operations.push_back(op);
+                    if (m_Engine->m_OperatorNameQuery)
+                    {
+                        if (compressorType == Operator::PLUGIN_INTERFACE)
+                        {
+                            auto pop = dynamic_cast<plugin::PluginOperator *>(op.get());
+                            pop->m_OperatorNameQuery = true;
+                        }
+                        else
+                        {
+                            auto m = MakeMessage("Operator", "OperatorFactory", "MakeOperator",
+                                                 "ADIOS2 compiled with " +
+                                                     OperatorTypeToString(compressorType) +
+                                                     " library, operator added",
+                                                 -1, helper::LogMode::EXCEPTION);
+                            throw MissingOperatorFailure(m, OperatorTypeToString(compressorType));
+                        }
+                    }
+                }
+                op->SetAccuracy(VB->GetAccuracyRequested());
                 core::Decompress(
                     IncomingData,
                     ((MetaArrayRecOperator *)writer_meta_base)->DataBlockSize[Read.BlockID],

source/utils/bpls/bpls.cpp

@@ -1010,7 +1010,9 @@ int doList_operators(core::Engine *fp, core::IO *io)
         variable->SetBlockSelection(0);                                                            \
         std::vector<T> dataV;                                                                      \
         dataV.resize(variable->SelectionSize());                                                   \
+        fp->m_OperatorNameQuery = true;                                                            \
         fp->Get(*variable, dataV, adios2::Mode::Sync);                                             \
+        fp->m_OperatorNameQuery = false;                                                           \
     }
                     ADIOS2_FOREACH_STDTYPE_1ARG(declare_template_instantiation)
 #undef declare_template_instantiation