[Tickets #14075] Large mailboxes takes many seconds to load and causes CPU at 100%

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Ticket URL: https://bugs.horde.org/ticket/14075
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  Ticket             | 14075
  Created By         | cunha17 at gmail.com
  Summary            | Large mailboxes takes many seconds to load and causes
                     | CPU at 100%
  Queue              | Horde Framework Packages
  Type               | Bug
  State              | Unconfirmed
  Priority           | 3. High
  Milestone          |
  Patch              | 1
  Owners             |
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cunha17 at gmail.com (2015-08-03 23:28) wrote:

The library in question is Horde_Imap_Client.

The class where the performance problem reside is  
Horde_Imap_Client_Data_Thread.

And the method causing the high CPU usage is _getAllIndices().

This method uses a simple iteration through _thead array (in my case  
having 8088 elements) and merges the keys of each sub-array with the  
previous one. So it calls array_merge and array_keys 8088 times:

protected function _getAllIndices()
     {
         $out = array();
         reset($this->_thread);
         while (list(,$v) = each($this->_thread)) {
             $out = array_merge($out, array_keys($v));
         }

         return $out;
     }

I replaced this iteration with this and the performance issue were gone:

protected function _getAllIndices()
     {
             return array_keys(call_user_func_array('array_replace',  
$this->_thread));
     }

Hope it helps and best regards,

Cristiano da Cunha Duarte