function apdqc_kill_metadata_lock in Asynchronous Prefetch Database Query Cache 7

Checks db processlist for metadata lock & kills query if waiting over 1s.

Parameters

string $thread_id: Name thread to check for the metadata lock.

Return value

bool TRUE if it did kill the query. FALSE if no killing was done.

3 calls to apdqc_kill_metadata_lock()

apdqc_admin_change_table_collation_queries in ./apdqc.admin.inc

Convert the table to the specified collation.

apdqc_convert_cache_index in ./apdqc.admin.inc

Converts a database index from one form to another.

apdqc_truncate_table in ./apdqc.mysql.inc

Empties out a database table in a non metadata locking fashion.

File

./apdqc.mysql.inc, line 979

APDQC Database interface code for MySQL database servers.

Code

function apdqc_kill_metadata_lock($thread_id) {
  $lock_found = TRUE;
  while ($lock_found) {

    // Check for a Metadata lock.
    // @ignore sql_curly
    $result = db_query("SELECT * FROM information_schema.processlist WHERE ID = :pid AND STATE LIKE 'Waiting for table metadata lock' LIMIT 1", array(
      ":pid" => $thread_id,
    ));
    foreach ($result as $record) {

      // Rename should not take over 1 second.
      if ($record->TIME >= 1) {

        // Kill query that is in a metadata lock state.
        db_query("KILL QUERY :pid", array(
          ":pid" => $thread_id,
        ));
        return TRUE;
      }

      // Wait 250ms.
      usleep(250000);

      // Goto top of while loop.
      continue 2;
    }

    // Metadata lock cleared.
    $lock_found = FALSE;
  }
  return FALSE;
}