Method resize

sql/sql_cache.cc:1296–1351

size_t Query_cache::resize(size_t query_cache_size_arg)
{
  size_t new_query_cache_size;
  DBUG_ENTER("Query_cache::resize");
  DBUG_PRINT("qcache", ("from %zu to %zu",query_cache_size,
			query_cache_size_arg));
  DBUG_ASSERT(initialized);

  lock_and_suspend();

  /*
    Wait for all readers and writers to exit. When the list of all queries
    is iterated over with a block level lock, we are done.
  */
  Query_cache_block *block= queries_blocks;
  if (block)
  {
    do
    {
      BLOCK_LOCK_WR(block);
      Query_cache_query *query= block->query();
      if (query->writer())
      {
        /*
           Drop the writer; this will cancel any attempts to store
           the processed statement associated with this writer.
         */
        query->writer()->first_query_block= NULL;
        query->writer(0);
        refused++;
      }
      query->unlock_n_destroy();
      block= block->next;
    } while (block != queries_blocks);
    queries_blocks= NULL; // avoid second destroying by free_cache
  }
  free_cache();

  query_cache_size= query_cache_size_arg;
  new_query_cache_size= init_cache();

  /*
    m_cache_status is internal query cache switch so switching it on/off
    will not be reflected on global_system_variables.query_cache_type
  */
  if (new_query_cache_size && global_system_variables.query_cache_type != 0)
  {
    DBUG_EXECUTE("check_querycache",check_integrity(1););
    m_cache_status= OK;                         // size > 0 => enable cache
  }
  else
    m_cache_status= DISABLED;                   // size 0 means the cache disabled

  unlock();
  DBUG_RETURN(new_query_cache_size);
}