Do not read rankTable in file encoding

Author: franzpoeschel

include/openPMD/Series.hpp

@@ -457,6 +457,18 @@ class Series : public Attributable
      */
     Series &setMeshesPath(std::string const &meshesPath);
 
+    /**
+     * @return True if there is a rankTable dataset defined for this Series.
+     *         False in write-only access modes.
+     *         Will indiscriminately return false in file encoding:
+     *         rankTable is not explicitly supported in file encoding,
+     *         finding out if one is defined would require opening all available
+     *         files. You may still call Series::rankTable() to retrieve the
+     *         rank table if you know that there is one, but note that it will
+     *         return the rank table from the file that was last opened.
+     */
+    bool hasRankTableRead();
+
     /**
      * @throw   no_such_attribute_error If optional attribute is not present.
      * @param collective Run this read operation collectively.
@@ -1008,6 +1020,8 @@ OPENPMD_private
      * steps?
      */
     [[nodiscard]] bool randomAccessSteps() const;
+
+    std::vector<std::string> availableDatasets();
 }; // Series
 
 namespace debug

src/Series.cpp

@@ -215,6 +215,38 @@ Series &Series::setMeshesPath(std::string const &mp)
     return *this;
 }
 
+std::vector<std::string> Series::availableDatasets()
+{
+    if (iterationEncoding() == IterationEncoding::variableBased &&
+        IOHandler()->m_backendAccess == Access::READ_RANDOM_ACCESS)
+    {
+        Parameter<Operation::ADVANCE> advance;
+        advance.mode =
+            Parameter<Operation::ADVANCE>::StepSelection{std::nullopt};
+        IOHandler()->enqueue(IOTask(this, std::move(advance)));
+    }
+    Parameter<Operation::LIST_DATASETS> listDatasets;
+    IOHandler()->enqueue(IOTask(this, listDatasets));
+    IOHandler()->flush(internal::defaultFlushParams);
+    return std::move(*listDatasets.datasets);
+}
+
+bool Series::hasRankTableRead()
+{
+    if (access::writeOnly(IOHandler()->m_frontendAccess))
+    {
+        return false;
+    }
+    auto &series = get();
+    if (series.m_rankTable.m_bufferedRead.has_value())
+    {
+        return true;
+    }
+    auto datasets = availableDatasets();
+    return std::find(datasets.begin(), datasets.end(), "rankTable") !=
+        datasets.end();
+}
+
 #if openPMD_HAVE_MPI
 chunk_assignment::RankMeta Series::rankTable(bool collective)
 #else
@@ -245,21 +277,9 @@ chunk_assignment::RankMeta Series::rankTable([[maybe_unused]] bool collective)
         IOHandler()->enqueue(IOTask(this, openFile));
 #endif
     }
-    if (iterationEncoding() == IterationEncoding::variableBased &&
-        IOHandler()->m_backendAccess == Access::READ_RANDOM_ACCESS)
-    {
-        Parameter<Operation::ADVANCE> advance;
-        advance.mode =
-            Parameter<Operation::ADVANCE>::StepSelection{std::nullopt};
-        IOHandler()->enqueue(IOTask(this, std::move(advance)));
-    }
-    Parameter<Operation::LIST_DATASETS> listDatasets;
-    IOHandler()->enqueue(IOTask(this, listDatasets));
-    IOHandler()->flush(internal::defaultFlushParams);
-    if (std::none_of(
-            listDatasets.datasets->begin(),
-            listDatasets.datasets->end(),
-            [](std::string const &str) { return str == "rankTable"; }))
+    auto datasets = availableDatasets();
+    if (std::find(datasets.begin(), datasets.end(), "rankTable") ==
+        datasets.end())
     {
         rankTable.m_bufferedRead = chunk_assignment::RankMeta{};
         return {};

src/binding/python/Series.cpp

@@ -442,6 +442,7 @@ this method.
         .def_property("base_path", &Series::basePath, &Series::setBasePath)
         .def_property(
             "meshes_path", &Series::meshesPath, &Series::setMeshesPath)
+        .def_property_readonly("has_rank_table_read", &Series::hasRankTableRead)
         .def("get_rank_table", &Series::rankTable, py::arg("collective"))
         .def("set_rank_table", &Series::setRankTable, py::arg("my_rank_info"))
         .def_property(

src/binding/python/openpmd_api/pipe/__main__.py

@@ -401,7 +401,10 @@ def __copy(self, src, dest, current_path="/data/"):
                             print("\t {0}".format(r))
                 # With linear read mode, we can only load the source rank table
                 # inside `read_iterations()` since it's a dataset.
-                self.inranks = src.get_rank_table(collective=True)
+                if src.has_rank_table_read:
+                    self.inranks = src.get_rank_table(collective=True)
+                else:
+                    self.inranks = {}
                 out_iteration = write_iterations[in_iteration.iteration_index]
                 sys.stdout.flush()
                 self.__copy(