Remove Schema::copyTable

Problem/Motivation

Schema::copyTable() was implemented because it was used at one point during Drupal 8 development. However it is no longer used, and can be safely removed from core.

Proposed resolution

Remove Schema::copyTable() method.

Remaining tasks

• Write a patch that removes the method, its uses, and tests from MySQL (and SQLite?)
• Write a change record since we're in late beta, and some developer may be confused.
• Consider follow-up issue regarding 8.1.x or 9.0.x, or add to meta discussion around database driver.

User interface changes

None

API changes

Yes. Schema::copyTable() will no longer be available in 8.0.0 for Drupal developers.

Original report by chx

Followup from #2056133: Add db_copy_table_schema The code wanted to be this:

    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 . '} INCLUDING ALL)');

Damien has this to say:

Sadly, this is not going to be enough, because indexes and constraints are globally-named on PostgreSQL. The server is likely going to rename those during the copy process, and it will not match our table_name + constraint name convention anymore. PostgreSQL support is critically broken due to several other issues, so let's not hold off this patch with PostgreSQL... but please add a TODO here.