[Tickets #14368] Improve EAS performance with large History tables

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Ticket URL: https://bugs.horde.org/ticket/14368
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  Ticket             | 14368
  Created By         | hannes.brunssen at ewetel.de
  Summary            | Improve EAS performance with large History tables
  Queue              | Synchronization
  Version            | FRAMEWORK_5_2
  Type               | Enhancement
  State              | New
  Priority           | 2. Medium
  Milestone          |
  Patch              |
  Owners             |
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hannes.brunssen at ewetel.de (2016-05-21 20:43) wrote:

We noticed a few devices that never send SYNC requests for collections  
like calendar oder contacts, because there are no changes. Without  
SYNC requests the activesync_state entries are not updated and the  
sync_mod values stay relatively low. With the low sync_mod values the  
number of history entries that has to be checked on every PING  
requests grow larger and larger. It takes a few seconds to check for  
updates in over a million history entries for a single calendar which  
is a growing part of our total database load. I don't know if this is  
a client bug or just normal behavior.

These lookups can be reduced if we update the sync state from time to  
time. This could be done if we override the getChanges method in  
Horde_ActiveSync_State_Sql:

public function getChanges(array $options = array())
{
	parent::getChanges($options);
	if ($this->_type == Horde_ActiveSync::REQUEST_TYPE_PING &&
			empty($this->_changes) &&
			$this->_lastSyncStamp < $this->_thisSyncStamp - 10000) {

		$this->_lastSyncStamp = $this->_thisSyncStamp;
		$this->_type = Horde_ActiveSync::REQUEST_TYPE_SYNC;
		$this->save();
		$this->_type = Horde_ActiveSync::REQUEST_TYPE_PING;
	}
	return $this->_changes;
}

The type change is a bit ugly, but the save method would clear the  
sync_data otherwise. That could be changed in the save method.

The update might only be needed on collections that support modseq,  
but the connector is not available from the state. I don't know if it  
would cause problems with mail folders, every 10000 seconds would be 8  
times per day which would be more than necessary.