colmap/src/base/database_test.cc

// Copyright (c) 2022, ETH Zurich and UNC Chapel Hill.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//
//     * Redistributions in binary form must reproduce the above copyright
//       notice, this list of conditions and the following disclaimer in the
//       documentation and/or other materials provided with the distribution.
//
//     * Neither the name of ETH Zurich and UNC Chapel Hill nor the names of
//       its contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// Author: Johannes L. Schoenberger (jsch-at-demuc-dot-de)

#define TEST_NAME "base/database"
#include "util/testing.h"

#include <thread>

#include "base/database.h"
#include "base/pose.h"

using namespace colmap;

const static std::string kMemoryDatabasePath = ":memory:";

BOOST_AUTO_TEST_CASE(TestOpenCloseConstructorDestructor) {
  Database database(kMemoryDatabasePath);
}

BOOST_AUTO_TEST_CASE(TestOpenClose) {
  Database database(kMemoryDatabasePath);
  database.Close();
}

BOOST_AUTO_TEST_CASE(TestTransaction) {
  Database database(kMemoryDatabasePath);
  DatabaseTransaction database_transaction(&database);
}

BOOST_AUTO_TEST_CASE(TestTransactionMultiThreaded) {
  Database database(kMemoryDatabasePath);

  std::thread thread1([&database]() {
    DatabaseTransaction database_transaction(&database);
    std::this_thread::sleep_for(std::chrono::milliseconds(100));
  });

  std::thread thread2([&database]() {
    DatabaseTransaction database_transaction(&database);
    std::this_thread::sleep_for(std::chrono::milliseconds(100));
  });

  thread1.join();
  thread2.join();
}

BOOST_AUTO_TEST_CASE(TestEmpty) {
  Database database(kMemoryDatabasePath);
  BOOST_CHECK_EQUAL(database.NumCameras(), 0);
  BOOST_CHECK_EQUAL(database.NumImages(), 0);
  BOOST_CHECK_EQUAL(database.NumKeypoints(), 0);
  BOOST_CHECK_EQUAL(database.MaxNumKeypoints(), 0);
  BOOST_CHECK_EQUAL(database.NumDescriptors(), 0);
  BOOST_CHECK_EQUAL(database.MaxNumDescriptors(), 0);
  BOOST_CHECK_EQUAL(database.NumMatches(), 0);
  BOOST_CHECK_EQUAL(database.NumMatchedImagePairs(), 0);
  BOOST_CHECK_EQUAL(database.NumVerifiedImagePairs(), 0);
}

BOOST_AUTO_TEST_CASE(TestImagePairToPairId) {
  BOOST_CHECK_EQUAL(Database::ImagePairToPairId(0, 0), 0);
  BOOST_CHECK_EQUAL(Database::ImagePairToPairId(0, 1), 1);
  BOOST_CHECK_EQUAL(Database::ImagePairToPairId(0, 2), 2);
  BOOST_CHECK_EQUAL(Database::ImagePairToPairId(0, 3), 3);
  BOOST_CHECK_EQUAL(Database::ImagePairToPairId(1, 2),
                    Database::kMaxNumImages + 2);
  for (image_t i = 0; i < 20; ++i) {
    for (image_t j = 0; j < 20; ++j) {
      const image_pair_t pair_id = Database::ImagePairToPairId(i, j);
      image_t image_id1;
      image_t image_id2;
      Database::PairIdToImagePair(pair_id, &image_id1, &image_id2);
      if (i < j) {
        BOOST_CHECK_EQUAL(i, image_id1);
        BOOST_CHECK_EQUAL(j, image_id2);
      } else {
        BOOST_CHECK_EQUAL(i, image_id2);
        BOOST_CHECK_EQUAL(j, image_id1);
      }
    }
  }
}

BOOST_AUTO_TEST_CASE(TestSwapImagePair) {
  BOOST_CHECK(!Database::SwapImagePair(0, 0));
  BOOST_CHECK(!Database::SwapImagePair(0, 1));
  BOOST_CHECK(Database::SwapImagePair(1, 0));
  BOOST_CHECK(!Database::SwapImagePair(1, 1));
}

BOOST_AUTO_TEST_CASE(TestCamera) {
  Database database(kMemoryDatabasePath);
  BOOST_CHECK_EQUAL(database.NumCameras(), 0);
  Camera camera;
  camera.InitializeWithName("SIMPLE_PINHOLE", 1.0, 1, 1);
  camera.SetCameraId(database.WriteCamera(camera));
  BOOST_CHECK_EQUAL(database.NumCameras(), 1);
  BOOST_CHECK_EQUAL(database.ExistsCamera(camera.CameraId()), true);
  BOOST_CHECK_EQUAL(database.ReadCamera(camera.CameraId()).CameraId(),
                    camera.CameraId());
  BOOST_CHECK_EQUAL(database.ReadCamera(camera.CameraId()).ModelId(),
                    camera.ModelId());
  BOOST_CHECK_EQUAL(database.ReadCamera(camera.CameraId()).FocalLength(),
                    camera.FocalLength());
  BOOST_CHECK_EQUAL(database.ReadCamera(camera.CameraId()).PrincipalPointX(),
                    camera.PrincipalPointX());
  BOOST_CHECK_EQUAL(database.ReadCamera(camera.CameraId()).PrincipalPointY(),
                    camera.PrincipalPointY());
  camera.SetFocalLength(2.0);
  database.UpdateCamera(camera);
  BOOST_CHECK_EQUAL(database.ReadCamera(camera.CameraId()).FocalLength(),
                    camera.FocalLength());
  Camera camera2 = camera;
  camera2.SetCameraId(camera.CameraId() + 1);
  database.WriteCamera(camera2, true);
  BOOST_CHECK_EQUAL(database.NumCameras(), 2);
  BOOST_CHECK_EQUAL(database.ExistsCamera(camera.CameraId()), true);
  BOOST_CHECK_EQUAL(database.ExistsCamera(camera2.CameraId()), true);
  BOOST_CHECK_EQUAL(database.ReadAllCameras().size(), 2);
  BOOST_CHECK_EQUAL(database.ReadAllCameras()[0].CameraId(), camera.CameraId());
  BOOST_CHECK_EQUAL(database.ReadAllCameras()[1].CameraId(),
                    camera2.CameraId());
  database.ClearCameras();
  BOOST_CHECK_EQUAL(database.NumCameras(), 0);
}

BOOST_AUTO_TEST_CASE(TestImage) {
  Database database(kMemoryDatabasePath);
  Camera camera;
  camera.InitializeWithName("SIMPLE_PINHOLE", 1.0, 1, 1);
  camera.SetCameraId(database.WriteCamera(camera));
  BOOST_CHECK_EQUAL(database.NumImages(), 0);
  Image image;
  image.SetName("test");
  image.SetCameraId(camera.CameraId());
  image.SetQvecPrior(Eigen::Vector4d(0.1, 0.2, 0.3, 0.4));
  image.SetTvecPrior(Eigen::Vector3d(0.1, 0.2, 0.3));
  image.SetImageId(database.WriteImage(image));
  BOOST_CHECK_EQUAL(database.NumImages(), 1);
  BOOST_CHECK_EQUAL(database.ExistsImage(image.ImageId()), true);
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).ImageId(),
                    image.ImageId());
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).CameraId(),
                    image.CameraId());
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).QvecPrior(0),
                    image.QvecPrior(0));
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).QvecPrior(1),
                    image.QvecPrior(1));
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).QvecPrior(2),
                    image.QvecPrior(2));
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).QvecPrior(3),
                    image.QvecPrior(3));
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).TvecPrior(0),
                    image.TvecPrior(0));
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).TvecPrior(1),
                    image.TvecPrior(1));
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).TvecPrior(2),
                    image.TvecPrior(2));
  image.TvecPrior(0) += 2;
  database.UpdateImage(image);
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).ImageId(),
                    image.ImageId());
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).CameraId(),
                    image.CameraId());
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).QvecPrior(0),
                    image.QvecPrior(0));
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).QvecPrior(1),
                    image.QvecPrior(1));
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).QvecPrior(2),
                    image.QvecPrior(2));
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).QvecPrior(3),
                    image.QvecPrior(3));
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).TvecPrior(0),
                    image.TvecPrior(0));
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).TvecPrior(1),
                    image.TvecPrior(1));
  BOOST_CHECK_EQUAL(database.ReadImage(image.ImageId()).TvecPrior(2),
                    image.TvecPrior(2));
  Image image2 = image;
  image2.SetName("test2");
  image2.SetImageId(image.ImageId() + 1);
  database.WriteImage(image2, true);
  BOOST_CHECK_EQUAL(database.NumImages(), 2);
  BOOST_CHECK_EQUAL(database.ExistsImage(image.ImageId()), true);
  BOOST_CHECK_EQUAL(database.ExistsImage(image2.ImageId()), true);
  BOOST_CHECK_EQUAL(database.ReadAllImages().size(), 2);
  database.ClearImages();
  BOOST_CHECK_EQUAL(database.NumImages(), 0);
}

BOOST_AUTO_TEST_CASE(TestKeypoints) {
  Database database(kMemoryDatabasePath);
  Camera camera;
  camera.SetCameraId(database.WriteCamera(camera));
  Image image;
  image.SetName("test");
  image.SetCameraId(camera.CameraId());
  image.SetImageId(database.WriteImage(image));
  BOOST_CHECK_EQUAL(database.NumKeypoints(), 0);
  BOOST_CHECK_EQUAL(database.NumKeypointsForImage(image.ImageId()), 0);
  const FeatureKeypoints keypoints = FeatureKeypoints(10);
  database.WriteKeypoints(image.ImageId(), keypoints);
  const FeatureKeypoints keypoints_read =
      database.ReadKeypoints(image.ImageId());
  BOOST_CHECK_EQUAL(keypoints.size(), keypoints_read.size());
  for (size_t i = 0; i < keypoints.size(); ++i) {
    BOOST_CHECK_EQUAL(keypoints[i].x, keypoints_read[i].x);
    BOOST_CHECK_EQUAL(keypoints[i].y, keypoints_read[i].y);
    BOOST_CHECK_EQUAL(keypoints[i].a11, keypoints_read[i].a11);
    BOOST_CHECK_EQUAL(keypoints[i].a12, keypoints_read[i].a12);
    BOOST_CHECK_EQUAL(keypoints[i].a21, keypoints_read[i].a21);
    BOOST_CHECK_EQUAL(keypoints[i].a22, keypoints_read[i].a22);
  }
  BOOST_CHECK_EQUAL(database.NumKeypoints(), 10);
  BOOST_CHECK_EQUAL(database.MaxNumKeypoints(), 10);
  BOOST_CHECK_EQUAL(database.NumKeypointsForImage(image.ImageId()), 10);
  const FeatureKeypoints keypoints2 = FeatureKeypoints(20);
  image.SetName("test2");
  image.SetImageId(database.WriteImage(image));
  database.WriteKeypoints(image.ImageId(), keypoints2);
  BOOST_CHECK_EQUAL(database.NumKeypoints(), 30);
  BOOST_CHECK_EQUAL(database.MaxNumKeypoints(), 20);
  BOOST_CHECK_EQUAL(database.NumKeypointsForImage(image.ImageId()), 20);
  database.ClearKeypoints();
  BOOST_CHECK_EQUAL(database.NumKeypoints(), 0);
  BOOST_CHECK_EQUAL(database.MaxNumKeypoints(), 0);
  BOOST_CHECK_EQUAL(database.NumKeypointsForImage(image.ImageId()), 0);
}

BOOST_AUTO_TEST_CASE(TestDescriptors) {
  Database database(kMemoryDatabasePath);
  Camera camera;
  camera.SetCameraId(database.WriteCamera(camera));
  Image image;
  image.SetName("test");
  image.SetCameraId(camera.CameraId());
  image.SetImageId(database.WriteImage(image));
  BOOST_CHECK_EQUAL(database.NumDescriptors(), 0);
  BOOST_CHECK_EQUAL(database.NumDescriptorsForImage(image.ImageId()), 0);
  const FeatureDescriptors descriptors = FeatureDescriptors::Random(10, 128);
  database.WriteDescriptors(image.ImageId(), descriptors);
  const FeatureDescriptors descriptors_read =
      database.ReadDescriptors(image.ImageId());
  BOOST_CHECK_EQUAL(descriptors.rows(), descriptors_read.rows());
  BOOST_CHECK_EQUAL(descriptors.cols(), descriptors_read.cols());
  for (FeatureDescriptors::Index r = 0; r < descriptors.rows(); ++r) {
    for (FeatureDescriptors::Index c = 0; c < descriptors.cols(); ++c) {
      BOOST_CHECK_EQUAL(descriptors(r, c), descriptors_read(r, c));
    }
  }
  BOOST_CHECK_EQUAL(database.NumDescriptors(), 10);
  BOOST_CHECK_EQUAL(database.MaxNumDescriptors(), 10);
  BOOST_CHECK_EQUAL(database.NumDescriptorsForImage(image.ImageId()), 10);
  const FeatureDescriptors descriptors2 = FeatureDescriptors(20, 128);
  image.SetName("test2");
  image.SetImageId(database.WriteImage(image));
  database.WriteDescriptors(image.ImageId(), descriptors2);
  BOOST_CHECK_EQUAL(database.NumDescriptors(), 30);
  BOOST_CHECK_EQUAL(database.MaxNumDescriptors(), 20);
  BOOST_CHECK_EQUAL(database.NumDescriptorsForImage(image.ImageId()), 20);
  database.ClearDescriptors();
  BOOST_CHECK_EQUAL(database.NumDescriptors(), 0);
  BOOST_CHECK_EQUAL(database.MaxNumDescriptors(), 0);
  BOOST_CHECK_EQUAL(database.NumDescriptorsForImage(image.ImageId()), 0);
}

BOOST_AUTO_TEST_CASE(TestMatches) {
  Database database(kMemoryDatabasePath);
  const image_t image_id1 = 1;
  const image_t image_id2 = 2;
  const FeatureMatches matches = FeatureMatches(1000);
  database.WriteMatches(image_id1, image_id2, matches);
  const FeatureMatches matches_read =
      database.ReadMatches(image_id1, image_id2);
  BOOST_CHECK_EQUAL(matches.size(), matches_read.size());
  for (size_t i = 0; i < matches.size(); ++i) {
    BOOST_CHECK_EQUAL(matches[i].point2D_idx1, matches_read[i].point2D_idx1);
    BOOST_CHECK_EQUAL(matches[i].point2D_idx2, matches_read[i].point2D_idx2);
  }
  BOOST_CHECK_EQUAL(database.ReadAllMatches().size(), 1);
  BOOST_CHECK_EQUAL(database.ReadAllMatches()[0].first,
                    Database::ImagePairToPairId(image_id1, image_id2));
  BOOST_CHECK_EQUAL(database.NumMatches(), 1000);
  database.DeleteMatches(image_id1, image_id2);
  BOOST_CHECK_EQUAL(database.NumMatches(), 0);
  database.WriteMatches(image_id1, image_id2, matches);
  BOOST_CHECK_EQUAL(database.NumMatches(), 1000);
  database.ClearMatches();
  BOOST_CHECK_EQUAL(database.NumMatches(), 0);
}

BOOST_AUTO_TEST_CASE(TestTwoViewGeometry) {
  Database database(kMemoryDatabasePath);
  const image_t image_id1 = 1;
  const image_t image_id2 = 2;
  TwoViewGeometry two_view_geometry;
  two_view_geometry.inlier_matches = FeatureMatches(1000);
  two_view_geometry.config =
      TwoViewGeometry::ConfigurationType::PLANAR_OR_PANORAMIC;
  two_view_geometry.F = Eigen::Matrix3d::Random();
  two_view_geometry.E = Eigen::Matrix3d::Random();
  two_view_geometry.H = Eigen::Matrix3d::Random();
  two_view_geometry.qvec = Eigen::Vector4d::Random();
  two_view_geometry.tvec = Eigen::Vector3d::Random();
  database.WriteTwoViewGeometry(image_id1, image_id2, two_view_geometry);
  const TwoViewGeometry two_view_geometry_read =
      database.ReadTwoViewGeometry(image_id1, image_id2);
  BOOST_CHECK_EQUAL(two_view_geometry.inlier_matches.size(),
                    two_view_geometry_read.inlier_matches.size());
  for (size_t i = 0; i < two_view_geometry_read.inlier_matches.size(); ++i) {
    BOOST_CHECK_EQUAL(two_view_geometry.inlier_matches[i].point2D_idx1,
                      two_view_geometry_read.inlier_matches[i].point2D_idx1);
    BOOST_CHECK_EQUAL(two_view_geometry.inlier_matches[i].point2D_idx2,
                      two_view_geometry_read.inlier_matches[i].point2D_idx2);
  }

  BOOST_CHECK_EQUAL(two_view_geometry.config, two_view_geometry_read.config);
  BOOST_CHECK_EQUAL(two_view_geometry.F, two_view_geometry_read.F);
  BOOST_CHECK_EQUAL(two_view_geometry.E, two_view_geometry_read.E);
  BOOST_CHECK_EQUAL(two_view_geometry.H, two_view_geometry_read.H);
  BOOST_CHECK_EQUAL(two_view_geometry.qvec, two_view_geometry_read.qvec);
  BOOST_CHECK_EQUAL(two_view_geometry.tvec, two_view_geometry_read.tvec);

  const TwoViewGeometry two_view_geometry_read_inv =
      database.ReadTwoViewGeometry(image_id2, image_id1);
  BOOST_CHECK_EQUAL(two_view_geometry_read_inv.inlier_matches.size(),
                    two_view_geometry_read.inlier_matches.size());
  for (size_t i = 0; i < two_view_geometry_read.inlier_matches.size(); ++i) {
    BOOST_CHECK_EQUAL(two_view_geometry_read_inv.inlier_matches[i].point2D_idx2,
                      two_view_geometry_read.inlier_matches[i].point2D_idx1);
    BOOST_CHECK_EQUAL(two_view_geometry_read_inv.inlier_matches[i].point2D_idx1,
                      two_view_geometry_read.inlier_matches[i].point2D_idx2);
  }

  BOOST_CHECK_EQUAL(two_view_geometry_read_inv.config,
                    two_view_geometry_read.config);
  BOOST_CHECK_EQUAL(two_view_geometry_read_inv.F.transpose(),
                    two_view_geometry_read.F);
  BOOST_CHECK_EQUAL(two_view_geometry_read_inv.E.transpose(),
                    two_view_geometry_read.E);
  BOOST_CHECK(two_view_geometry_read_inv.H.inverse().eval().isApprox(
      two_view_geometry_read.H));

  Eigen::Vector4d read_inv_qvec_inv;
  Eigen::Vector3d read_inv_tvec_inv;
  InvertPose(two_view_geometry_read_inv.qvec, two_view_geometry_read_inv.tvec,
             &read_inv_qvec_inv, &read_inv_tvec_inv);
  BOOST_CHECK_EQUAL(read_inv_qvec_inv, two_view_geometry_read.qvec);
  BOOST_CHECK(read_inv_tvec_inv.isApprox(two_view_geometry_read.tvec));

  std::vector<image_pair_t> image_pair_ids;
  std::vector<TwoViewGeometry> two_view_geometries;
  database.ReadTwoViewGeometries(&image_pair_ids, &two_view_geometries);
  BOOST_CHECK_EQUAL(image_pair_ids.size(), 1);
  BOOST_CHECK_EQUAL(two_view_geometries.size(), 1);
  BOOST_CHECK_EQUAL(image_pair_ids[0],
                    Database::ImagePairToPairId(image_id1, image_id2));
  BOOST_CHECK_EQUAL(two_view_geometry.config, two_view_geometries[0].config);
  BOOST_CHECK_EQUAL(two_view_geometry.F, two_view_geometries[0].F);
  BOOST_CHECK_EQUAL(two_view_geometry.E, two_view_geometries[0].E);
  BOOST_CHECK_EQUAL(two_view_geometry.H, two_view_geometries[0].H);
  BOOST_CHECK_EQUAL(two_view_geometry.qvec, two_view_geometries[0].qvec);
  BOOST_CHECK_EQUAL(two_view_geometry.tvec, two_view_geometries[0].tvec);
  BOOST_CHECK_EQUAL(two_view_geometry.inlier_matches.size(),
                    two_view_geometries[0].inlier_matches.size());
  std::vector<std::pair<image_t, image_t>> image_pairs;
  std::vector<int> num_inliers;
  database.ReadTwoViewGeometryNumInliers(&image_pairs, &num_inliers);
  BOOST_CHECK_EQUAL(image_pairs.size(), 1);
  BOOST_CHECK_EQUAL(num_inliers.size(), 1);
  BOOST_CHECK_EQUAL(image_pairs[0].first, image_id1);
  BOOST_CHECK_EQUAL(image_pairs[0].second, image_id2);
  BOOST_CHECK_EQUAL(num_inliers[0], two_view_geometry.inlier_matches.size());
  BOOST_CHECK_EQUAL(database.NumInlierMatches(), 1000);
  database.DeleteInlierMatches(image_id1, image_id2);
  BOOST_CHECK_EQUAL(database.NumInlierMatches(), 0);
  database.WriteTwoViewGeometry(image_id1, image_id2, two_view_geometry);
  BOOST_CHECK_EQUAL(database.NumInlierMatches(), 1000);
  database.ClearTwoViewGeometries();
  BOOST_CHECK_EQUAL(database.NumInlierMatches(), 0);
}

BOOST_AUTO_TEST_CASE(TestMerge) {
  Database database1(kMemoryDatabasePath);
  Database database2(kMemoryDatabasePath);

  Camera camera;
  camera.InitializeWithName("SIMPLE_PINHOLE", 1.0, 1, 1);
  camera.SetCameraId(database1.WriteCamera(camera));
  camera.SetCameraId(database2.WriteCamera(camera));

  Image image;
  image.SetCameraId(camera.CameraId());
  image.SetQvecPrior(Eigen::Vector4d(0.1, 0.2, 0.3, 0.4));
  image.SetTvecPrior(Eigen::Vector3d(0.1, 0.2, 0.3));

  image.SetName("test1");
  const image_t image_id1 = database1.WriteImage(image);
  image.SetName("test2");
  const image_t image_id2 = database1.WriteImage(image);
  image.SetName("test3");
  const image_t image_id3 = database2.WriteImage(image);
  image.SetName("test4");
  const image_t image_id4 = database2.WriteImage(image);

  auto keypoints1 = FeatureKeypoints(10);
  keypoints1[0].x = 100;
  auto keypoints2 = FeatureKeypoints(20);
  keypoints2[0].x = 200;
  auto keypoints3 = FeatureKeypoints(30);
  keypoints3[0].x = 300;
  auto keypoints4 = FeatureKeypoints(40);
  keypoints4[0].x = 400;

  const auto descriptors1 = FeatureDescriptors::Random(10, 128);
  const auto descriptors2 = FeatureDescriptors::Random(20, 128);
  const auto descriptors3 = FeatureDescriptors::Random(30, 128);
  const auto descriptors4 = FeatureDescriptors::Random(40, 128);

  database1.WriteKeypoints(image_id1, keypoints1);
  database1.WriteKeypoints(image_id2, keypoints2);
  database2.WriteKeypoints(image_id3, keypoints3);
  database2.WriteKeypoints(image_id4, keypoints4);
  database1.WriteDescriptors(image_id1, descriptors1);
  database1.WriteDescriptors(image_id2, descriptors2);
  database2.WriteDescriptors(image_id3, descriptors3);
  database2.WriteDescriptors(image_id4, descriptors4);
  database1.WriteMatches(image_id1, image_id2, FeatureMatches(10));
  database2.WriteMatches(image_id3, image_id4, FeatureMatches(10));
  database1.WriteTwoViewGeometry(image_id1, image_id2, TwoViewGeometry());
  database2.WriteTwoViewGeometry(image_id3, image_id4, TwoViewGeometry());

  Database merged_database(kMemoryDatabasePath);
  Database::Merge(database1, database2, &merged_database);
  BOOST_CHECK_EQUAL(merged_database.NumCameras(), 2);
  BOOST_CHECK_EQUAL(merged_database.NumImages(), 4);
  BOOST_CHECK_EQUAL(merged_database.NumKeypoints(), 100);
  BOOST_CHECK_EQUAL(merged_database.NumDescriptors(), 100);
  BOOST_CHECK_EQUAL(merged_database.NumMatches(), 20);
  BOOST_CHECK_EQUAL(merged_database.NumInlierMatches(), 0);
  BOOST_CHECK_EQUAL(merged_database.ReadAllImages()[0].CameraId(), 1);
  BOOST_CHECK_EQUAL(merged_database.ReadAllImages()[1].CameraId(), 1);
  BOOST_CHECK_EQUAL(merged_database.ReadAllImages()[2].CameraId(), 2);
  BOOST_CHECK_EQUAL(merged_database.ReadAllImages()[3].CameraId(), 2);
  BOOST_CHECK_EQUAL(merged_database.ReadKeypoints(1).size(), 10);
  BOOST_CHECK_EQUAL(merged_database.ReadKeypoints(2).size(), 20);
  BOOST_CHECK_EQUAL(merged_database.ReadKeypoints(3).size(), 30);
  BOOST_CHECK_EQUAL(merged_database.ReadKeypoints(4).size(), 40);
  BOOST_CHECK_EQUAL(merged_database.ReadKeypoints(1)[0].x, 100);
  BOOST_CHECK_EQUAL(merged_database.ReadKeypoints(2)[0].x, 200);
  BOOST_CHECK_EQUAL(merged_database.ReadKeypoints(3)[0].x, 300);
  BOOST_CHECK_EQUAL(merged_database.ReadKeypoints(4)[0].x, 400);
  BOOST_CHECK_EQUAL(merged_database.ReadDescriptors(1).size(),
                    descriptors1.size());
  BOOST_CHECK_EQUAL(merged_database.ReadDescriptors(2).size(),
                    descriptors2.size());
  BOOST_CHECK_EQUAL(merged_database.ReadDescriptors(3).size(),
                    descriptors3.size());
  BOOST_CHECK_EQUAL(merged_database.ReadDescriptors(4).size(),
                    descriptors4.size());
  BOOST_CHECK(merged_database.ExistsMatches(1, 2));
  BOOST_CHECK(!merged_database.ExistsMatches(2, 3));
  BOOST_CHECK(!merged_database.ExistsMatches(2, 4));
  BOOST_CHECK(merged_database.ExistsMatches(3, 4));
  merged_database.ClearAllTables();
  BOOST_CHECK_EQUAL(merged_database.NumCameras(), 0);
  BOOST_CHECK_EQUAL(merged_database.NumImages(), 0);
  BOOST_CHECK_EQUAL(merged_database.NumKeypoints(), 0);
  BOOST_CHECK_EQUAL(merged_database.NumDescriptors(), 0);
  BOOST_CHECK_EQUAL(merged_database.NumMatches(), 0);
}