Issue #2056133 by chx, dawehner, plach, alexpott: Add db_copy_table().

core/includes/database.inc

@@ -679,6 +679,23 @@ function db_rename_table($table, $new_name) {
   return Database::getConnection()->schema()->renameTable($table, $new_name);
 }
 
+/**
+ * Copies the structure of a table.
+ *
+ * @param string $source
+ *   The name of the table to be copied.
+ * @param string $destination
+ *   The name for the new table.
+ *
+ * @return \Drupal\Core\Database\StatementInterface
+ *   The result of the executed query.
+ *
+ * @see \Drupal\Core\Database\Schema::copyTable()
+ */
+function db_copy_table_schema($source, $destination) {
+  return Database::getConnection()->schema()->copyTable($source, $destination);
+}
+
 /**
  * Drops a table.
  *

core/lib/Drupal/Core/Database/Driver/mysql/Schema.php

@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Database\Driver\mysql;
 
+use Drupal\Component\Utility\String;
 use Drupal\Core\Database\Database;
 use Drupal\Core\Database\Query\Condition;
 use Drupal\Core\Database\SchemaObjectExistsException;
@@ -327,6 +328,21 @@ class Schema extends DatabaseSchema {
     return TRUE;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function copyTable($source, $destination) {
+    if (!$this->tableExists($source)) {
+      throw new SchemaObjectDoesNotExistException(String::format("Cannot copy @source to @destination: table @source doesn't exist.", array('@source' => $source, '@destination' => $destination)));
+    }
+    if ($this->tableExists($destination)) {
+      throw new SchemaObjectExistsException(String::format("Cannot copy @source to @destination: table @destination already exists.", array('@source' => $source, '@destination' => $destination)));
+    }
+
+    $info = $this->getPrefixInfo($destination);
+    return $this->connection->query('CREATE TABLE `' . $info['table'] . '` LIKE {' . $source . '}');
+  }
+
   public function addField($table, $field, $spec, $keys_new = array()) {
     if (!$this->tableExists($table)) {
       throw new SchemaObjectDoesNotExistException(t("Cannot add field @table.@field: table doesn't exist.", array('@field' => $field, '@table' => $table)));

core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php

@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Database\Driver\pgsql;
 
+use Drupal\Component\Utility\String;
 use Drupal\Core\Database\Database;
 use Drupal\Core\Database\Query\Condition;
 use Drupal\Core\Database\SchemaObjectExistsException;
@@ -348,6 +349,16 @@ class Schema extends DatabaseSchema {
     $this->connection->query('ALTER TABLE {' . $table . '} RENAME TO ' . $prefixInfo['table']);
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function copyTable($source, $destination) {
+    // @TODO The server is likely going to rename indexes and constraints
+    //   during the copy process, and it will not match our
+    //   table_name + constraint name convention anymore.
+    throw new \Exception('Not implemented, see https://drupal.org/node/2061879');
+  }
+
   public function dropTable($table) {
     if (!$this->tableExists($table)) {
       return FALSE;

core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php

@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Database\Driver\sqlite;
 
+use Drupal\Component\Utility\String;
 use Drupal\Core\Database\SchemaObjectExistsException;
 use Drupal\Core\Database\SchemaObjectDoesNotExistException;
 use Drupal\Core\Database\Schema as DatabaseSchema;
@@ -272,6 +273,20 @@ class Schema extends DatabaseSchema {
     }
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function copyTable($source, $destination) {
+    if (!$this->tableExists($source)) {
+      throw new SchemaObjectDoesNotExistException(String::format("Cannot copy @source to @destination: table @source doesn't exist.", array('@source' => $source, '@destination' => $destination)));
+    }
+    if ($this->tableExists($destination)) {
+      throw new SchemaObjectExistsException(String::format("Cannot copy @source to @destination: table @destination already exists.", array('@source' => $source, '@destination' => $destination)));
+    }
+
+    $this->createTable($destination, $this->introspectSchema($source));
+  }
+
   public function dropTable($table) {
     if (!$this->tableExists($table)) {
       return FALSE;

core/lib/Drupal/Core/Database/Schema.php

@@ -407,6 +407,24 @@ abstract class Schema implements PlaceholderInterface {
    */
   abstract public function dropTable($table);
 
+  /**
+   * Copies the table schema.
+   *
+   * @param string $source
+   *   The name of the table to be used as source.
+   * @param string $destination
+   *   The name of the table to be used as destination.
+   *
+   * @return \Drupal\Core\Database\StatementInterface
+   *   The result of the executed query.
+   *
+   * @throws \Drupal\Core\Database\SchemaObjectExistsException
+   *   Thrown when the source table does not exist.
+   * @throws \Drupal\Core\Database\SchemaObjectDoesNotExistException
+   *   Thrown when the destination table already exists.
+   */
+  abstract public function copyTable($source, $destination);
+
   /**
    * Add a new field to a table.
    *

core/modules/system/lib/Drupal/system/Tests/Database/SchemaTest.php

@@ -8,6 +8,8 @@
 namespace Drupal\system\Tests\Database;
 
 use Drupal\Core\Database\Database;
+use Drupal\Core\Database\SchemaObjectDoesNotExistException;
+use Drupal\Core\Database\SchemaObjectExistsException;
 use Drupal\simpletest\UnitTestBase;
 
 /**
@@ -87,6 +89,38 @@ class SchemaTest extends UnitTestBase {
     $index_exists = Database::getConnection()->schema()->indexExists('test_table2', 'test_field');
     $this->assertTrue($index_exists, 'Index was renamed.');
 
+    // Copy the schema of the table.
+    db_copy_table_schema('test_table2', 'test_table3');
+
+    // Index should be copied.
+    $index_exists = Database::getConnection()->schema()->indexExists('test_table3', 'test_field');
+    $this->assertTrue($index_exists, 'Index was copied.');
+
+    // Data should still exist on the old table but not on the new one.
+    $count = db_select('test_table2')->countQuery()->execute()->fetchField();
+    $this->assertEqual($count, 1, 'The old table still has its content.');
+    $count = db_select('test_table3')->countQuery()->execute()->fetchField();
+    $this->assertEqual($count, 0, 'The new table has no content.');
+
+    // Ensure that the proper exceptions are thrown for db_copy_table_schema().
+    $fail = FALSE;
+    try {
+      db_copy_table_schema('test_table4', 'test_table5');
+    }
+    catch (SchemaObjectDoesNotExistException $e) {
+      $fail = TRUE;
+    }
+    $this->assertTrue($fail, 'Ensure that db_copy_table_schema() throws an exception when the source table does not exist.');
+
+    $fail = FALSE;
+    try {
+      db_copy_table_schema('test_table2', 'test_table3');
+    }
+    catch (SchemaObjectExistsException $e) {
+      $fail = TRUE;
+    }
+    $this->assertTrue($fail, 'Ensure that db_copy_table_schema() throws an exception when the destination table already exists.');
+
     // We need the default so that we can insert after the rename.
     db_field_set_default('test_table2', 'test_field', 0);
     $this->assertFalse($this->tryInsert(), 'Insert into the old table failed.');
@@ -154,9 +188,9 @@ class SchemaTest extends UnitTestBase {
    */
   function tryInsert($table = 'test_table') {
     try {
-       db_insert($table)
-         ->fields(array('id' => mt_rand(10, 20)))
-         ->execute();
+      db_insert($table)
+        ->fields(array('id' => mt_rand(10, 20)))
+        ->execute();
       return TRUE;
     }
     catch (\Exception $e) {
@@ -227,8 +261,8 @@ class SchemaTest extends UnitTestBase {
   function tryUnsignedInsert($table_name, $column_name) {
     try {
       db_insert($table_name)
-         ->fields(array($column_name => -1))
-         ->execute();
+        ->fields(array($column_name => -1))
+        ->execute();
       return TRUE;
     }
     catch (\Exception $e) {