diff --git a/core/includes/common.inc b/core/includes/common.inc
index c9fdd6f..218bae4 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -1333,14 +1333,6 @@ function drupal_flush_all_caches() {
   // actually loaded.
   $module_handler->loadAll();
 
-  // Rebuild the schema and cache a fully-built schema based on new module data.
-  // This is necessary for any invocation of index.php, because setting cache
-  // table entries requires schema information and that occurs during bootstrap
-  // before any modules are loaded, so if there is no cached schema,
-  // drupal_get_schema() will try to generate one, but with no loaded modules,
-  // it will return nothing.
-  drupal_get_schema(NULL, TRUE);
-
   // Rebuild all information based on new module data.
   $module_handler->invokeAll('rebuild');
 
diff --git a/core/includes/schema.inc b/core/includes/schema.inc
index fdd0df5..501b3e2 100644
--- a/core/includes/schema.inc
+++ b/core/includes/schema.inc
@@ -5,7 +5,6 @@
  * Schema API handling functions.
  */
 
-use Drupal\Core\Cache\Cache;
 use Drupal\Core\Database\Database;
 
 /**
@@ -19,83 +18,6 @@
 const SCHEMA_UNINSTALLED = -1;
 
 /**
- * Gets the schema definition of a table, or the whole database schema.
- *
- * The returned schema will include any modifications made by any
- * module that implements hook_schema_alter().
- *
- * @param string $table
- *   The name of the table. If not given, the schema of all tables is returned.
- * @param bool $rebuild
- *   If TRUE, the schema will be rebuilt instead of retrieved from the cache.
- */
-function drupal_get_schema($table = NULL, $rebuild = FALSE) {
-  static $schema;
-
-  if ($rebuild || !isset($schema)) {
-    $schema = drupal_get_complete_schema($rebuild);
-  }
-
-  if (!isset($table)) {
-    return $schema;
-  }
-  if (isset($schema[$table])) {
-    return $schema[$table];
-  }
-  else {
-    return FALSE;
-  }
-}
-
-/**
- * Gets the whole database schema.
- *
- * The returned schema will include any modifications made by any
- * module that implements hook_schema_alter().
- *
- * @param bool $rebuild
- *   If TRUE, the schema will be rebuilt instead of retrieved from the cache.
- */
-function drupal_get_complete_schema($rebuild = FALSE) {
-  static $schema;
-
-  if (!isset($schema) || $rebuild) {
-    // Try to load the schema from cache.
-    if (!$rebuild && $cached = \Drupal::cache()->get('schema')) {
-      $schema = $cached->data;
-    }
-    // Otherwise, rebuild the schema cache.
-    else {
-      $schema = array();
-      // Load the .install files to get hook_schema.
-      \Drupal::moduleHandler()->loadAllIncludes('install');
-
-      require_once __DIR__ . '/common.inc';
-      // Invoke hook_schema for all modules.
-      foreach (\Drupal::moduleHandler()->getImplementations('schema') as $module) {
-        // Cast the result of hook_schema() to an array, as a NULL return value
-        // would cause array_merge() to set the $schema variable to NULL as well.
-        // That would break modules which use $schema further down the line.
-        $current = (array) \Drupal::moduleHandler()->invoke($module, 'schema');
-        // Set 'module' and 'name' keys for each table, and remove descriptions,
-        // as they needlessly slow down \Drupal::cache()->get() for every single request.
-        _drupal_schema_initialize($current, $module);
-        $schema = array_merge($schema, $current);
-      }
-      \Drupal::moduleHandler()->alter('schema', $schema);
-
-      // If the schema is empty, avoid saving it: some database engines require
-      // the schema to perform queries, and this could lead to infinite loops.
-      if (!empty($schema)) {
-        \Drupal::cache()->set('schema', $schema, Cache::PERMANENT);
-      }
-    }
-  }
-
-  return $schema;
-}
-
-/**
  * Returns an array of available schema versions for a module.
  *
  * @param string $module
@@ -199,7 +121,7 @@ function drupal_set_installed_schema_version($module, $version) {
  *   The module for which the tables will be created.
  */
 function drupal_install_schema($module) {
-  $schema = drupal_get_schema_unprocessed($module);
+  $schema = drupal_get_module_schema($module);
   _drupal_schema_initialize($schema, $module, FALSE);
 
   foreach ($schema as $name => $table) {
@@ -224,7 +146,7 @@ function drupal_install_schema($module) {
  *      \Drupal\Component\Utility\SafeMarkup::checkPlain().
  */
 function drupal_uninstall_schema($module) {
-  $schema = drupal_get_schema_unprocessed($module);
+  $schema = drupal_get_module_schema($module);
   _drupal_schema_initialize($schema, $module, FALSE);
 
   foreach ($schema as $table) {
@@ -235,30 +157,19 @@ function drupal_uninstall_schema($module) {
 }
 
 /**
- * Returns the unprocessed and unaltered version of a module's schema.
- *
- * Use this function only if you explicitly need the original
- * specification of a schema, as it was defined in a module's
- * hook_schema(). No additional default values will be set,
- * hook_schema_alter() is not invoked and these unprocessed
- * definitions won't be cached.
+ * Returns a module's schema.
  *
  * This function can be used to retrieve a schema specification in
  * hook_schema(), so it allows you to derive your tables from existing
  * specifications.
  *
- * It is also used by drupal_install_schema() and
- * drupal_uninstall_schema() to ensure that a module's tables are
- * created exactly as specified without any changes introduced by a
- * module that implements hook_schema_alter().
- *
  * @param string $module
  *   The module to which the table belongs.
  * @param string $table
  *   The name of the table. If not given, the module's complete schema
  *   is returned.
  */
-function drupal_get_schema_unprocessed($module, $table = NULL) {
+function drupal_get_module_schema($module, $table = NULL) {
   // Load the .install file to get hook_schema.
   module_load_install($module);
   $schema = \Drupal::moduleHandler()->invoke($module, 'schema');
diff --git a/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php b/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php
index 21672fb..d3c1762 100644
--- a/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php
+++ b/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php
@@ -424,7 +424,6 @@ protected function alterTable($table, $old_schema, $new_schema, array $mapping =
    *   Name of the table.
    * @return
    *   An array representing the schema, from drupal_get_schema().
-   * @see drupal_get_schema()
    */
   protected function introspectSchema($table) {
     $mapped_fields = array_flip($this->getFieldTypeMap());
diff --git a/core/lib/Drupal/Core/Database/database.api.php b/core/lib/Drupal/Core/Database/database.api.php
index cd6459b..dc2e208 100644
--- a/core/lib/Drupal/Core/Database/database.api.php
+++ b/core/lib/Drupal/Core/Database/database.api.php
@@ -474,8 +474,6 @@ function hook_query_TAG_alter(Drupal\Core\Database\Query\AlterableInterface $que
  *   array, the key is a table name and the value is a table structure
  *   definition.
  *
- * @see hook_schema_alter()
- *
  * @ingroup schemaapi
  */
 function hook_schema() {
@@ -535,30 +533,5 @@ function hook_schema() {
 }
 
 /**
- * Perform alterations to existing database schemas.
- *
- * When a module modifies the database structure of another module (by
- * changing, adding or removing fields, keys or indexes), it should
- * implement hook_schema_alter() to update the default $schema to take its
- * changes into account.
- *
- * See hook_schema() for details on the schema definition structure.
- *
- * @param $schema
- *   Nested array describing the schemas for all modules.
- *
- * @ingroup schemaapi
- */
-function hook_schema_alter(&$schema) {
-  // Add field to existing schema.
-  $schema['users']['fields']['timezone_id'] = array(
-    'type' => 'int',
-    'not null' => TRUE,
-    'default' => 0,
-    'description' => 'Per-user timezone configuration.',
-  );
-}
-
-/**
  * @} End of "addtogroup hooks".
  */
diff --git a/core/lib/Drupal/Core/Extension/ModuleInstaller.php b/core/lib/Drupal/Core/Extension/ModuleInstaller.php
index d99c9dd..e523943 100644
--- a/core/lib/Drupal/Core/Extension/ModuleInstaller.php
+++ b/core/lib/Drupal/Core/Extension/ModuleInstaller.php
@@ -205,9 +205,6 @@ public function install(array $module_list, $enable_dependencies = TRUE) {
         // Update the kernel to include it.
         $this->updateKernel($module_filenames);
 
-        // Refresh the schema to include it.
-        drupal_get_schema(NULL, TRUE);
-
         // Allow modules to react prior to the installation of a module.
         $this->moduleHandler->invokeAll('module_preinstall', array($module));
 
diff --git a/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php b/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
index d17f065..5634000 100644
--- a/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
+++ b/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
@@ -147,15 +147,6 @@ public function buildForm(array $form, FormStateInterface $form_state) {
     // work during installation.
     $form['#attached']['drupalSettings']['copyFieldValue']['edit-site-mail'] = ['edit-account-mail'];
 
-    // Cache a fully-built schema. This is necessary for any invocation of
-    // index.php because: (1) setting cache table entries requires schema
-    // information, (2) that occurs during bootstrap before any module are
-    // loaded, so (3) if there is no cached schema, drupal_get_schema() will
-    // try to generate one but with no loaded modules will return nothing.
-    //
-    // @todo Move this to the 'install_finished' task?
-    drupal_get_schema(NULL, TRUE);
-
     $form['site_information'] = array(
       '#type' => 'fieldgroup',
       '#title' => $this->t('Site information'),
diff --git a/core/modules/simpletest/simpletest.module b/core/modules/simpletest/simpletest.module
index 94e12e9..254be0c 100644
--- a/core/modules/simpletest/simpletest.module
+++ b/core/modules/simpletest/simpletest.module
@@ -552,7 +552,7 @@ function simpletest_clean_environment() {
  */
 function simpletest_clean_database() {
   $tables = db_find_tables(Database::getConnection()->prefixTables('{simpletest}') . '%');
-  $schema = drupal_get_schema_unprocessed('simpletest');
+  $schema = drupal_get_module_schema('simpletest');
   $count = 0;
   foreach (array_diff_key($tables, $schema) as $table) {
     // Strip the prefix and skip tables without digits following "simpletest",
diff --git a/core/modules/simpletest/src/KernelTestBase.php b/core/modules/simpletest/src/KernelTestBase.php
index e8d1ba2..481b031 100644
--- a/core/modules/simpletest/src/KernelTestBase.php
+++ b/core/modules/simpletest/src/KernelTestBase.php
@@ -405,7 +405,7 @@ protected function installConfig(array $modules) {
    *   found in the module specified.
    */
   protected function installSchema($module, $tables) {
-    // drupal_get_schema_unprocessed() is technically able to install a schema
+    // drupal_get_module_schema() is technically able to install a schema
     // of a non-enabled module, but its ability to load the module's .install
     // file depends on many other factors. To prevent differences in test
     // behavior and non-reproducible test failures, we only allow the schema of
@@ -417,7 +417,7 @@ protected function installSchema($module, $tables) {
     }
     $tables = (array) $tables;
     foreach ($tables as $table) {
-      $schema = drupal_get_schema_unprocessed($module, $table);
+      $schema = drupal_get_module_schema($module, $table);
       if (empty($schema)) {
         throw new \RuntimeException(format_string("Unknown '@table' table schema in '@module' module.", array(
           '@module' => $module,
@@ -426,10 +426,6 @@ protected function installSchema($module, $tables) {
       }
       $this->container->get('database')->schema()->createTable($table, $schema);
     }
-    // We need to refresh the schema cache, as any call to drupal_get_schema()
-    // would not know of/return the schema otherwise.
-    // @todo Refactor Schema API to make this obsolete.
-    drupal_get_schema(NULL, TRUE);
     $this->pass(format_string('Installed %module tables: %tables.', array(
       '%tables' => '{' . implode('}, {', $tables) . '}',
       '%module' => $module,
diff --git a/core/modules/simpletest/src/Tests/KernelTestBaseTest.php b/core/modules/simpletest/src/Tests/KernelTestBaseTest.php
index 6d92255..9d0af0e 100644
--- a/core/modules/simpletest/src/Tests/KernelTestBaseTest.php
+++ b/core/modules/simpletest/src/Tests/KernelTestBaseTest.php
@@ -108,8 +108,8 @@ function testEnableModulesInstall() {
     $this->assertFalse(in_array($module, $list), "{$module}_hook_info() in \Drupal::moduleHandler()->getImplementations() not found.");
 
     $this->assertFalse(db_table_exists($table), "'$table' database table not found.");
-    $schema = drupal_get_schema($table, TRUE);
-    $this->assertFalse($schema, "'$table' table schema not found.");
+    $schema = drupal_get_module_schema($module, $table);
+    $this->assertTrue($schema, "'$table' table schema found.");
 
     // Install the module.
     \Drupal::service('module_installer')->install(array($module));
@@ -122,7 +122,7 @@ function testEnableModulesInstall() {
     $this->assertTrue(in_array($module, $list), "{$module}_hook_info() in \Drupal::moduleHandler()->getImplementations() found.");
 
     $this->assertTrue(db_table_exists($table), "'$table' database table found.");
-    $schema = drupal_get_schema($table);
+    $schema = drupal_get_module_schema($module, $table);
     $this->assertTrue($schema, "'$table' table schema found.");
   }
 
@@ -154,9 +154,7 @@ function testInstallSchema() {
     $this->assertTrue(db_table_exists($table), "'$table' database table found.");
 
     // Verify that the schema is known to Schema API.
-    $schema = drupal_get_schema();
-    $this->assertTrue($schema[$table], "'$table' table found in schema.");
-    $schema = drupal_get_schema($table);
+    $schema = drupal_get_module_schema($module, $table);
     $this->assertTrue($schema, "'$table' table schema found.");
 
     // Verify that a unknown table from an enabled module throws an error.
@@ -169,7 +167,7 @@ function testInstallSchema() {
       $this->pass('Exception for non-retrievable schema found.');
     }
     $this->assertFalse(db_table_exists($table), "'$table' database table not found.");
-    $schema = drupal_get_schema($table);
+    $schema = drupal_get_module_schema($module, $table);
     $this->assertFalse($schema, "'$table' table schema not found.");
 
     // Verify that a table from a unknown module cannot be installed.
@@ -183,14 +181,14 @@ function testInstallSchema() {
       $this->pass('Exception for non-retrievable schema found.');
     }
     $this->assertFalse(db_table_exists($table), "'$table' database table not found.");
-    $schema = drupal_get_schema($table);
-    $this->assertFalse($schema, "'$table' table schema not found.");
+    $schema = drupal_get_module_schema($module, $table);
+    $this->assertTrue($schema, "'$table' table schema found.");
 
     // Verify that the same table can be installed after enabling the module.
     $this->enableModules(array($module));
     $this->installSchema($module, $table);
     $this->assertTrue(db_table_exists($table), "'$table' database table found.");
-    $schema = drupal_get_schema($table);
+    $schema = drupal_get_module_schema($module, $table);
     $this->assertTrue($schema, "'$table' table schema found.");
   }
 
diff --git a/core/modules/system/src/Tests/Database/InsertDefaultsTest.php b/core/modules/system/src/Tests/Database/InsertDefaultsTest.php
index d5f60dd..576d53f 100644
--- a/core/modules/system/src/Tests/Database/InsertDefaultsTest.php
+++ b/core/modules/system/src/Tests/Database/InsertDefaultsTest.php
@@ -23,7 +23,7 @@ function testDefaultInsert() {
     $query = db_insert('test')->useDefaults(array('job'));
     $id = $query->execute();
 
-    $schema = drupal_get_schema('test');
+    $schema = drupal_get_module_schema('database_test', 'test');
 
     $job = db_query('SELECT job FROM {test} WHERE id = :id', array(':id' => $id))->fetchField();
     $this->assertEqual($job, $schema['fields']['job']['default'], 'Default field value is set.');
@@ -56,7 +56,7 @@ function testDefaultInsertWithFields() {
       ->useDefaults(array('job'));
     $id = $query->execute();
 
-    $schema = drupal_get_schema('test');
+    $schema = drupal_get_module_schema('database_test', 'test');
 
     $job = db_query('SELECT job FROM {test} WHERE id = :id', array(':id' => $id))->fetchField();
     $this->assertEqual($job, $schema['fields']['job']['default'], 'Default field value is set.');
diff --git a/core/modules/system/src/Tests/Entity/EntityFieldTest.php b/core/modules/system/src/Tests/Entity/EntityFieldTest.php
index c932856..0ac3dc7 100644
--- a/core/modules/system/src/Tests/Entity/EntityFieldTest.php
+++ b/core/modules/system/src/Tests/Entity/EntityFieldTest.php
@@ -58,6 +58,7 @@ protected function setUp() {
     }
 
     // Create the test field.
+    module_load_install('entity_test');
     entity_test_install();
 
     // Install required default configuration for filter module.
diff --git a/core/modules/system/src/Tests/Entity/EntityLanguageTestBase.php b/core/modules/system/src/Tests/Entity/EntityLanguageTestBase.php
index 48eac84..666ea03 100644
--- a/core/modules/system/src/Tests/Entity/EntityLanguageTestBase.php
+++ b/core/modules/system/src/Tests/Entity/EntityLanguageTestBase.php
@@ -61,6 +61,7 @@ protected function setUp() {
     $this->installConfig(array('language'));
 
     // Create the test field.
+    module_load_install('entity_test');
     entity_test_install();
 
     // Enable translations for the test entity type.
diff --git a/core/modules/system/src/Tests/Entity/EntityValidationTest.php b/core/modules/system/src/Tests/Entity/EntityValidationTest.php
index d4358fc..4df83b1 100644
--- a/core/modules/system/src/Tests/Entity/EntityValidationTest.php
+++ b/core/modules/system/src/Tests/Entity/EntityValidationTest.php
@@ -45,6 +45,7 @@ protected function setUp() {
     parent::setUp();
 
     // Create the test field.
+    module_load_install('entity_test');
     entity_test_install();
 
     // Install required default configuration for filter module.
diff --git a/core/modules/system/src/Tests/Module/ModuleTestBase.php b/core/modules/system/src/Tests/Module/ModuleTestBase.php
index 1bd44bb..d421d43 100644
--- a/core/modules/system/src/Tests/Module/ModuleTestBase.php
+++ b/core/modules/system/src/Tests/Module/ModuleTestBase.php
@@ -59,7 +59,7 @@ function assertTableCount($base_table, $count = TRUE) {
    *   The name of the module.
    */
   function assertModuleTablesExist($module) {
-    $tables = array_keys(drupal_get_schema_unprocessed($module));
+    $tables = array_keys(drupal_get_module_schema($module));
     $tables_exist = TRUE;
     foreach ($tables as $table) {
       if (!db_table_exists($table)) {
@@ -76,7 +76,7 @@ function assertModuleTablesExist($module) {
    *   The name of the module.
    */
   function assertModuleTablesDoNotExist($module) {
-    $tables = array_keys(drupal_get_schema_unprocessed($module));
+    $tables = array_keys(drupal_get_module_schema($module));
     $tables_exist = FALSE;
     foreach ($tables as $table) {
       if (db_table_exists($table)) {
diff --git a/core/modules/system/tests/modules/module_test/module_test.install b/core/modules/system/tests/modules/module_test/module_test.install
index 53dfa33..e90fc57 100644
--- a/core/modules/system/tests/modules/module_test/module_test.install
+++ b/core/modules/system/tests/modules/module_test/module_test.install
@@ -28,7 +28,7 @@ function module_test_schema() {
  * Implements hook_install().
  */
 function module_test_install() {
-  $schema = drupal_get_schema('module_test');
+  $schema = drupal_get_module_schema('module_test', 'module_test');
   db_insert('module_test')
     ->fields(array(
       'data' => $schema['fields']['data']['type'],