Bug fix: Ensure correct data retrieval for global cell order in dense…

… reader, avoiding fill values (#5413)

`slab_dim` is being calculated incorrectly in
`DenseReader::cell_slab_overlaps_range`, causing global cell order reads
to return some fill values. After this fix, `slab_dim` remains unchanged
for row-major or column-major requests, but for global order requests,
cell order is used to determine `slab_dim`.

The initial issue was also verified with TileDB-Py, and after applying
this fix, the results are as expected.

[sc-60301]

---
TYPE: NO_HISTORY | BUG
DESC: Fix incorrect `slab_dim` calculation in
`DenseReader::cell_slab_overlaps_range` to prevent fill values in global
cell order reads.

---------

Co-authored-by: Ypatia Tsavliri <[email protected]>

test/CMakeLists.txt

@@ -112,6 +112,7 @@ set(TILEDB_UNIT_TEST_SOURCES
   src/unit-ctx.cc
   src/unit-current-domain-rest.cc
   src/unit-dense-reader.cc
+  src/unit-dense-global-order-reader.cc
   src/unit-DenseTiler.cc
   src/unit-dimension.cc
   src/unit-duplicates.cc

test/src/unit-dense-global-order-reader.cc

@@ -0,0 +1,107 @@
+/**
+ * @file   unit-dense-global-order-reader.cc
+ *
+ * @section LICENSE
+ *
+ * The MIT License
+ *
+ * @copyright Copyright (c) 2025 TileDB, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <test/support/tdb_catch.h>
+#include "test/support/src/vfs_helpers.h"
+#include "tiledb/sm/cpp_api/tiledb"
+
+using namespace tiledb;
+
+static void create_array(Context& ctx, const std::string& array_uri);
+static void write_array(
+    Context& ctx, const std::string& array_uri, tiledb_layout_t layout);
+
+TEST_CASE(
+    "SC-60301: Read data with global cell order returns fill values",
+    "[dense-reader][bug][global-cell-order][fixed][sc60301]") {
+  test::VFSTestSetup vfs_test_setup;
+  const std::string array_uri =
+      vfs_test_setup.array_uri("dense_global_cell_order");
+  Context ctx{vfs_test_setup.ctx()};
+
+  // Test setup
+  create_array(ctx, array_uri);
+  auto write_layout =
+      GENERATE(TILEDB_ROW_MAJOR, TILEDB_COL_MAJOR, TILEDB_GLOBAL_ORDER);
+  write_array(ctx, array_uri, write_layout);
+
+  Array array(ctx, array_uri, TILEDB_READ);
+  Subarray subarray(ctx, array);
+  subarray.set_subarray({1, 2, 1, 2});
+  std::vector<int> a_read;
+  a_read.resize(4);
+  Query query(ctx, array);
+  query.set_subarray(subarray)
+      .set_layout(TILEDB_GLOBAL_ORDER)
+      .set_data_buffer("a", a_read);
+
+  REQUIRE(query.submit() == Query::Status::COMPLETE);
+
+  if (write_layout == TILEDB_ROW_MAJOR) {
+    REQUIRE(a_read[0] == 1);
+    REQUIRE(a_read[1] == 3);
+    REQUIRE(a_read[2] == 2);
+    REQUIRE(a_read[3] == 4);
+  } else {
+    REQUIRE(a_read[0] == 1);
+    REQUIRE(a_read[1] == 2);
+    REQUIRE(a_read[2] == 3);
+    REQUIRE(a_read[3] == 4);
+  }
+
+  array.close();
+}
+
+void create_array(Context& ctx, const std::string& array_uri) {
+  auto obj = Object::object(ctx, array_uri);
+  if (obj.type() != Object::Type::Invalid) {
+    Object::remove(ctx, array_uri);
+  }
+
+  Domain domain(ctx);
+  domain.add_dimension(Dimension::create<int>(ctx, "d1", {{1, 2}}, 2))
+      .add_dimension(Dimension::create<int>(ctx, "d2", {{1, 2}}, 2));
+
+  // Create the array schema with col-major cell order and tile order
+  ArraySchema schema(ctx, TILEDB_DENSE);
+  schema.set_domain(domain)
+      .set_order({{TILEDB_COL_MAJOR, TILEDB_COL_MAJOR}})
+      .add_attribute(Attribute::create<int>(ctx, "a"));
+  Array::create(ctx, array_uri, schema);
+}
+
+void write_array(
+    Context& ctx, const std::string& array_uri, tiledb_layout_t layout) {
+  std::vector<int> data = {1, 2, 3, 4};
+  Array array(ctx, array_uri, TILEDB_WRITE);
+  Query query(ctx, array);
+  query.set_layout(layout).set_data_buffer("a", data);
+  REQUIRE(query.submit() == Query::Status::COMPLETE);
+  query.finalize();
+  array.close();
+}

tiledb/sm/query/readers/dense_reader.cc

@@ -1539,7 +1539,12 @@ tuple<bool, uint64_t, uint64_t> DenseReader::cell_slab_overlaps_range(
     const NDRange& ndrange,
     const std::vector<DimType>& coords,
     const uint64_t length) {
-  const unsigned slab_dim = (layout_ == Layout::COL_MAJOR) ? 0 : dim_num - 1;
+  const auto cell_order = array_schema_.cell_order();
+  const unsigned slab_dim =
+      (layout_ == Layout::ROW_MAJOR ||
+       (layout_ == Layout::GLOBAL_ORDER && cell_order == Layout::ROW_MAJOR)) ?
+          dim_num - 1 :
+          0;
   const DimType slab_start = coords[slab_dim];
   const DimType slab_end = slab_start + length - 1;