From a9d0bace0f1088805fb44d92baefc59745507d5f Mon Sep 17 00:00:00 2001
From: Ian Chen <ichen@openrobotics.org>
Date: Fri, 5 Sep 2025 10:57:20 -0700
Subject: [PATCH 1/2] Skip Model sdf serialization

Signed-off-by: Ian Chen <ichen@openrobotics.org>
---
 include/gz/sim/components/Model.hh | 54 ++++++------------------------
 1 file changed, 10 insertions(+), 44 deletions(-)

diff --git a/include/gz/sim/components/Model.hh b/include/gz/sim/components/Model.hh
index 3889790338..a61ef36f36 100644
--- a/include/gz/sim/components/Model.hh
+++ b/include/gz/sim/components/Model.hh
@@ -43,50 +43,15 @@ namespace serializers
     public: static std::ostream &Serialize(std::ostream &_out,
                 const sdf::Model &_model)
     {
-      sdf::ElementPtr modelElem = _model.Element();
-      if (!modelElem)
-      {
-        gzwarn << "Unable to serialize sdf::Model" << std::endl;
-        return _out;
-      }
-
-      bool skip = false;
-      if (modelElem->HasElement("pose"))
-      {
-        sdf::ElementPtr poseElem = modelElem->GetElement("pose");
-        if (poseElem->GetAttribute("relative_to")->GetSet())
-        {
-          // Skip serializing models with //pose/@relative_to attribute
-          // since deserialization will fail. This could be a nested model.
-          // see https://github.com/gazebosim/gz-sim/issues/1071
-          // Once https://github.com/gazebosim/sdformat/issues/820 is
-          // resolved, there should be an API that returns sdf::Errors objects
-          // instead of printing console msgs so it would be easier to ignore
-          // specific errors in Deserialize.
-          static bool warned = false;
-          if (!warned)
-          {
-            gzwarn << "Skipping serialization / deserialization for models "
-                    << "with //pose/@relative_to attribute."
-                    << std::endl;
-            warned = true;
-          }
-          skip = true;
-        }
-      }
-
-      if (!skip)
-      {
-        _out << "<?xml version=\"1.0\" ?>"
-              << "<sdf version='" << SDF_PROTOCOL_VERSION << "'>"
-              << modelElem->ToString("")
-              << "</sdf>";
-
-      }
-      else
-      {
-        _out << "";
-      }
+      // Skip serialization of model sdf
+      // \todo(iche033) It was found that deserialization is
+      // very expensive, which impacts initial load time of a world with many
+      // entities. Currently only the server consumes ModelSdf components
+      // so let's skip serialization until either the deserialization
+      // performance is improved or when the GUI needs the to use Model SDF
+      // components.
+      // see, https://github.com/gazebosim/sdformat/issues/1478
+      _out << "";
       return _out;
     }
 
@@ -104,6 +69,7 @@ namespace serializers
       }
 
       // Its super expensive to create an SDFElement for some reason
+      // https://github.com/gazebosim/sdformat/issues/1478
       sdf::Root root;
       sdf::Errors errors = root.LoadSdfString(sdf);
       if (!root.Model())

From a53c290774073071275d481f992387600343a678 Mon Sep 17 00:00:00 2001
From: Ian Chen <ichen@openrobotics.org>
Date: Tue, 9 Sep 2025 15:51:46 -0700
Subject: [PATCH 2/2] remove more code, fix test

Signed-off-by: Ian Chen <ichen@openrobotics.org>
---
 include/gz/sim/components/Model.hh | 22 ++++------------------
 test/integration/components.cc     |  6 ++++--
 2 files changed, 8 insertions(+), 20 deletions(-)

diff --git a/include/gz/sim/components/Model.hh b/include/gz/sim/components/Model.hh
index a61ef36f36..f784553cdd 100644
--- a/include/gz/sim/components/Model.hh
+++ b/include/gz/sim/components/Model.hh
@@ -41,7 +41,7 @@ namespace serializers
     /// \param[in] _time Model to stream
     /// \return The stream.
     public: static std::ostream &Serialize(std::ostream &_out,
-                const sdf::Model &_model)
+                const sdf::Model &)
     {
       // Skip serialization of model sdf
       // \todo(iche033) It was found that deserialization is
@@ -60,25 +60,11 @@ namespace serializers
     /// \param[out] _model Model to populate
     /// \return The stream.
     public: static std::istream &Deserialize(std::istream &_in,
-                sdf::Model &_model)
+                sdf::Model &)
     {
-      std::string sdf(std::istreambuf_iterator<char>(_in), {});
-      if (sdf.empty())
-      {
-        return _in;
-      }
-
-      // Its super expensive to create an SDFElement for some reason
+      // Its super expensive to create an SDFElement for some reason.
+      // So seriazliation / deserialization of model sdf is skipped
       // https://github.com/gazebosim/sdformat/issues/1478
-      sdf::Root root;
-      sdf::Errors errors = root.LoadSdfString(sdf);
-      if (!root.Model())
-      {
-        gzwarn << "Unable to deserialize sdf::Model " << sdf<< std::endl;
-        return _in;
-      }
-
-      _model = *root.Model();
       return _in;
     }
   };
diff --git a/test/integration/components.cc b/test/integration/components.cc
index 37e75f4bbf..c96bd9a625 100644
--- a/test/integration/components.cc
+++ b/test/integration/components.cc
@@ -1276,8 +1276,10 @@ TEST_F(ComponentsTest, ModelSdf)
   std::istringstream istr(ostr.str());
   comp2.Deserialize(istr);
 
-  EXPECT_EQ("my_model", comp2.Data().Name());
-  EXPECT_EQ(1u, comp2.Data().LinkCount());
+  // Model sdf serialization / deserialization is disabled due to perf issue
+  // https://github.com/gazebosim/sdformat/issues/1478
+  // EXPECT_EQ("my_model", comp2.Data().Name());
+  // EXPECT_EQ(1u, comp2.Data().LinkCount());
 }
 
 /////////////////////////////////////////////////