Remove unused *ParallelQueries() database connection methods

Summary:
`executeParallelQueries()` is never called as `supportsParallelQueries()` returns `false` both in `AphrontDatabaseConnection` and `AphrontMySQLDatabaseConnection`.
Thus remove this unused code which was intentionally meant for HHVM which does not support PHP>=7 anyway.

P.S. Dear Facebook, if you are using this, let us know. We don't want to hurt your legacy Phabricator installation.

Closes T15919

Test Plan: Grep for both functions.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15919

Differential Revision: https://we.phorge.it/D25789

src/infrastructure/storage/connection/AphrontDatabaseConnection.php

@@ -63,10 +63,6 @@ abstract class AphrontDatabaseConnection
     return false;
   }
 
-  public function supportsParallelQueries() {
-    return false;
-  }
-
   public function setReadOnly($read_only) {
     $this->readOnly = $read_only;
     return $this;

src/infrastructure/storage/connection/mysql/AphrontMySQLDatabaseConnection.php

@@ -145,79 +145,6 @@ final class AphrontMySQLDatabaseConnection
     mysql_free_result($result);
   }
 
-  public function supportsParallelQueries() {
-    // fb_parallel_query() doesn't support results with different columns.
-    return false;
-  }
-
-  /**
-   * @phutil-external-symbol function fb_parallel_query
-   */
-  public function executeParallelQueries(
-    array $queries,
-    array $conns = array()) {
-    assert_instances_of($conns, __CLASS__);
-
-    $map = array();
-    $is_write = false;
-    foreach ($queries as $id => $query) {
-      $is_write = $is_write || $this->checkWrite($query);
-      $conn = idx($conns, $id, $this);
-
-      $host = $conn->getConfiguration('host');
-      $port = 0;
-      $match = null;
-      if (preg_match('/(.+):(.+)/', $host, $match)) {
-        list(, $host, $port) = $match;
-      }
-
-      $pass = $conn->getConfiguration('pass');
-      if ($pass instanceof PhutilOpaqueEnvelope) {
-        $pass = $pass->openEnvelope();
-      }
-
-      $map[$id] = array(
-        'sql' => $query,
-        'ip' => $host,
-        'port' => $port,
-        'username' => $conn->getConfiguration('user'),
-        'password' => $pass,
-        'db' => $conn->getConfiguration('database'),
-      );
-    }
-
-    $profiler = PhutilServiceProfiler::getInstance();
-    $call_id = $profiler->beginServiceCall(
-      array(
-        'type'    => 'multi-query',
-        'queries' => $queries,
-        'write'   => $is_write,
-      ));
-
-    $map = fb_parallel_query($map);
-
-    $profiler->endServiceCall($call_id, array());
-
-    $results = array();
-    $pos = 0;
-    $err_pos = 0;
-    foreach ($queries as $id => $query) {
-      $errno = idx(idx($map, 'errno', array()), $err_pos);
-      $err_pos++;
-      if ($errno) {
-        try {
-          $this->throwQueryCodeException($errno, $map['error'][$id]);
-        } catch (Exception $ex) {
-          $results[$id] = $ex;
-        }
-        continue;
-      }
-      $results[$id] = $map['result'][$pos];
-      $pos++;
-    }
-    return $results;
-  }
-
   protected function fetchAssoc($result) {
     return mysql_fetch_assoc($result);
   }

src/infrastructure/storage/future/QueryFuture.php

@@ -56,18 +56,6 @@ final class QueryFuture extends Future {
     }
 
     if (!$this->conn->supportsAsyncQueries()) {
-      if ($this->conn->supportsParallelQueries()) {
-        $queries = array();
-        $conns = array();
-        foreach (self::$futures as $id => $future) {
-          $queries[$id] = $future->query;
-          $conns[$id] = $future->conn;
-        }
-        $results = $this->conn->executeParallelQueries($queries, $conns);
-        $this->processResults($results);
-        return true;
-      }
-
       $conns = array();
       $conn_queries = array();
       foreach (self::$futures as $id => $future) {