ogr2ogr: transfer relationships (when possible) from source dataset to target dataset

apps/ogr2ogr_lib.cpp

@@ -2217,6 +2217,88 @@ GDALVectorTranslateCreateCopy(GDALDriver *poDriver, const char *pszDest,
     return poOut;
 }
 
+/************************************************************************/
+/*                           CopyRelationships()                        */
+/************************************************************************/
+
+static void CopyRelationships(GDALDataset *poODS, GDALDataset *poDS)
+{
+    if (!poODS->GetDriver()->GetMetadataItem(GDAL_DCAP_CREATE_RELATIONSHIP))
+        return;
+
+    const auto aosRelationshipNames = poDS->GetRelationshipNames();
+    if (aosRelationshipNames.empty())
+        return;
+
+    // Collect target layer names
+    std::set<std::string> oSetDestLayerNames;
+    for (const auto &poLayer : poDS->GetLayers())
+    {
+        oSetDestLayerNames.insert(poLayer->GetName());
+    }
+
+    // Iterate over all source relationships
+    for (const auto &osRelationshipName : aosRelationshipNames)
+    {
+        const auto poSrcRelationship =
+            poDS->GetRelationship(osRelationshipName);
+        if (!poSrcRelationship)
+            continue;
+
+        // Skip existing relationship of the same name
+        if (poODS->GetRelationship(osRelationshipName))
+            continue;
+
+        bool canAdd = true;
+        const auto &osLeftTableName = poSrcRelationship->GetLeftTableName();
+        if (!osLeftTableName.empty() &&
+            !cpl::contains(oSetDestLayerNames, osLeftTableName))
+        {
+            CPLDebug("GDALVectorTranslate",
+                     "Skipping relationship %s because its left table (%s) "
+                     "does not exist in target dataset",
+                     osRelationshipName.c_str(), osLeftTableName.c_str());
+            canAdd = false;
+        }
+
+        const auto &osRightTableName = poSrcRelationship->GetRightTableName();
+        if (!osRightTableName.empty() &&
+            !cpl::contains(oSetDestLayerNames, osRightTableName))
+        {
+            CPLDebug("GDALVectorTranslate",
+                     "Skipping relationship %s because its right table (%s) "
+                     "does not exist in target dataset",
+                     osRelationshipName.c_str(), osRightTableName.c_str());
+            canAdd = false;
+        }
+
+        const auto &osMappingTableName =
+            poSrcRelationship->GetMappingTableName();
+        if (!osMappingTableName.empty() &&
+            !cpl::contains(oSetDestLayerNames, osMappingTableName))
+        {
+            CPLDebug("GDALVectorTranslate",
+                     "Skipping relationship %s because its mapping table (%s) "
+                     "does not exist in target dataset",
+                     osRelationshipName.c_str(), osMappingTableName.c_str());
+            canAdd = false;
+        }
+
+        if (canAdd)
+        {
+            std::string osFailureReason;
+            if (!poODS->AddRelationship(
+                    std::make_unique<GDALRelationship>(*poSrcRelationship),
+                    osFailureReason))
+            {
+                CPLDebug("GDALVectorTranslate",
+                         "Cannot add relationship %s: %s",
+                         osRelationshipName.c_str(), osFailureReason.c_str());
+            }
+        }
+    }
+}
+
 /************************************************************************/
 /*                           GDALVectorTranslate()                      */
 /************************************************************************/
@@ -3590,6 +3672,9 @@ GDALDatasetH GDALVectorTranslate(const char *pszDest, GDALDatasetH hDstDS,
                 GDALDestroyScaledProgress(pProgressArg);
         }
     }
+
+    CopyRelationships(poODS, poDS);
+
     /* -------------------------------------------------------------------- */
     /*      Process DS style table                                          */
     /* -------------------------------------------------------------------- */

autotest/utilities/test_ogr2ogr_lib.py

@@ -3008,3 +3008,76 @@ def my_handler(errorClass, errno, msg):
         "2022/05/31 12:34:56",
         "2022/05/31 12:34:56+1230",
     ]
+
+
+###############################################################################
+
+
+@gdaltest.enable_exceptions()
+@pytest.mark.require_driver("GPKG")
+def test_ogr2ogr_lib_transfer_gpkg_relationships(tmp_vsimem):
+
+    out_filename = str(tmp_vsimem / "relationships.gpkg")
+    gdal.VectorTranslate(out_filename, "../ogr/data/gpkg/relation_mapping_table.gpkg")
+
+    with gdal.OpenEx(out_filename) as ds:
+        assert ds.GetRelationshipNames() == ["a_b_attributes"]
+        relationship = ds.GetRelationship("a_b_attributes")
+        assert relationship.GetLeftTableName() == "a"
+        assert relationship.GetRightTableName() == "b"
+        assert relationship.GetMappingTableName() == "my_mapping_table"
+
+    gdal.VectorTranslate(
+        out_filename,
+        "../ogr/data/gpkg/relation_mapping_table.gpkg",
+        layers=["a", "my_mapping_table"],
+    )
+    with gdal.OpenEx(out_filename) as ds:
+        assert ds.GetRelationshipNames() is None
+
+    gdal.VectorTranslate(
+        out_filename,
+        "../ogr/data/gpkg/relation_mapping_table.gpkg",
+        layers=["b", "my_mapping_table"],
+    )
+    with gdal.OpenEx(out_filename) as ds:
+        assert ds.GetRelationshipNames() is None
+
+    gdal.VectorTranslate(
+        out_filename, "../ogr/data/gpkg/relation_mapping_table.gpkg", layers=["a", "b"]
+    )
+    with gdal.OpenEx(out_filename) as ds:
+        assert ds.GetRelationshipNames() is None
+
+
+###############################################################################
+
+
+@gdaltest.enable_exceptions()
+@pytest.mark.require_driver("OpenFileGDB")
+def test_ogr2ogr_lib_transfer_filegdb_relationships(tmp_vsimem):
+
+    out_filename = str(tmp_vsimem / "relationships.gdb")
+    gdal.VectorTranslate(
+        out_filename, "../ogr/data/filegdb/relationships.gdb", format="OpenFileGDB"
+    )
+
+    with gdal.OpenEx(out_filename) as ds:
+        assert set(ds.GetRelationshipNames()) == set(
+            [
+                "composite_many_to_many",
+                "composite_one_to_one",
+                "points__ATTACHREL",
+                "simple_attributed",
+                "simple_backward_message_direction",
+                "simple_both_message_direction",
+                "simple_forward_message_direction",
+                "simple_many_to_many",
+                "simple_one_to_many",
+                "simple_relationship_one_to_one",
+            ]
+        )
+        relationship = ds.GetRelationship("composite_many_to_many")
+        assert relationship.GetLeftTableName() == "table6"
+        assert relationship.GetRightTableName() == "table7"
+        assert relationship.GetMappingTableName() == "composite_many_to_many"

ogr/ogrsf_frmts/gpkg/ogrgeopackagedatasource.cpp

@@ -1679,8 +1679,10 @@ int GDALGeoPackageDataset::Open(GDALOpenInfo *poOpenInfo,
                      "is_in_gpkg_contents, 'table' AS object_type "
                      "FROM gpkgext_relations WHERE "
                      "lower(mapping_table_name) NOT IN (SELECT "
-                     "lower(table_name) FROM "
-                     "gpkg_contents)";
+                     "lower(table_name) FROM gpkg_contents) AND "
+                     "EXISTS (SELECT 1 FROM sqlite_master WHERE "
+                     "type IN ('table', 'view') AND "
+                     "lower(name) = lower(mapping_table_name))";
         }
         if (EQUAL(pszListAllTables, "YES") ||
             (!bHasASpatialOrAttributes && EQUAL(pszListAllTables, "AUTO")))
@@ -2185,7 +2187,9 @@ void GDALGeoPackageDataset::LoadRelationshipsUsingRelatedTablesExtension() const
             const int nMappingTableCount = SQLGetInteger(hDB, pszSQL, nullptr);
             sqlite3_free(pszSQL);
 
-            if (nMappingTableCount < 1)
+            if (nMappingTableCount < 1 &&
+                !const_cast<GDALGeoPackageDataset *>(this)->GetLayerByName(
+                    pszMappingTableName))
             {
                 CPLError(CE_Warning, CPLE_AppDefined,
                          "Relationship mapping table %s does not exist",

ogr/ogrsf_frmts/openfilegdb/ogropenfilegdbdatasource_write.cpp

@@ -1881,6 +1881,9 @@ bool OGROpenFileGDBDataSource::AddRelationship(
     std::unique_ptr<GDALRelationship> &&relationship,
     std::string &failureReason)
 {
+    if (FlushCache(false) != CE_None)
+        return false;
+
     const std::string relationshipName(relationship->GetName());
     if (eAccess != GA_Update)
     {