Preamble

When using server-side processing with DataTables, it can be quite intensive on your server having an Ajax call every time the user performs some kind of interaction - you can effectively DDOS your server with your own application!

This example shows how you might over-come this by modifying the request set to the server to retrieve more information than is actually required for a single page's display. This means that the user can page multiple times (5 times the display size is the default) before a request must be made of the server. Paging is typically the most common interaction performed with a DataTable, so this can be most beneficial to your server's resource usage. Of course the pipeline must be cleared for interactions other than paging (sorting, filtering etc), but that's the trade off that can be made (sending extra information is cheep - while another XHR is expensive).

Live example

Initialisation code

var oCache = {
	iCacheLower: -1
};

function fnSetKey( aoData, sKey, mValue )
{
	for ( var i=0, iLen=aoData.length ; i<iLen ; i++ )
	{
		if ( aoData[i].name == sKey )
		{
			aoData[i].value = mValue;
		}
	}
}

function fnGetKey( aoData, sKey )
{
	for ( var i=0, iLen=aoData.length ; i<iLen ; i++ )
	{
		if ( aoData[i].name == sKey )
		{
			return aoData[i].value;
		}
	}
	return null;
}

function fnDataTablesPipeline ( sSource, aoData, fnCallback ) {
	var iPipe = 5; /* Ajust the pipe size */
	
	var bNeedServer = false;
	var sEcho = fnGetKey(aoData, "sEcho");
	var iRequestStart = fnGetKey(aoData, "iDisplayStart");
	var iRequestLength = fnGetKey(aoData, "iDisplayLength");
	var iRequestEnd = iRequestStart + iRequestLength;
	oCache.iDisplayStart = iRequestStart;
	
	/* outside pipeline? */
	if ( oCache.iCacheLower < 0 || iRequestStart < oCache.iCacheLower || iRequestEnd > oCache.iCacheUpper )
	{
		bNeedServer = true;
	}
	
	/* sorting etc changed? */
	if ( oCache.lastRequest && !bNeedServer )
	{
		for( var i=0, iLen=aoData.length ; i<iLen ; i++ )
		{
			if ( aoData[i].name != "iDisplayStart" && aoData[i].name != "iDisplayLength" && aoData[i].name != "sEcho" )
			{
				if ( aoData[i].value != oCache.lastRequest[i].value )
				{
					bNeedServer = true;
					break;
				}
			}
		}
	}
	
	/* Store the request for checking next time around */
	oCache.lastRequest = aoData.slice();
	
	if ( bNeedServer )
	{
		if ( iRequestStart < oCache.iCacheLower )
		{
			iRequestStart = iRequestStart - (iRequestLength*(iPipe-1));
			if ( iRequestStart < 0 )
			{
				iRequestStart = 0;
			}
		}
		
		oCache.iCacheLower = iRequestStart;
		oCache.iCacheUpper = iRequestStart + (iRequestLength * iPipe);
		oCache.iDisplayLength = fnGetKey( aoData, "iDisplayLength" );
		fnSetKey( aoData, "iDisplayStart", iRequestStart );
		fnSetKey( aoData, "iDisplayLength", iRequestLength*iPipe );
		
		$.getJSON( sSource, aoData, function (json) { 
			/* Callback processing */
			oCache.lastJson = jQuery.extend(true, {}, json);
			
			if ( oCache.iCacheLower != oCache.iDisplayStart )
			{
				json.aaData.splice( 0, oCache.iDisplayStart-oCache.iCacheLower );
			}
			json.aaData.splice( oCache.iDisplayLength, json.aaData.length );
			
			fnCallback(json)
		} );
	}
	else
	{
		json = jQuery.extend(true, {}, oCache.lastJson);
		json.sEcho = sEcho; /* Update the echo for each response */
		json.aaData.splice( 0, iRequestStart-oCache.iCacheLower );
		json.aaData.splice( iRequestLength, json.aaData.length );
		fnCallback(json);
		return;
	}
}

$(document).ready(function() {
	$('#example').dataTable( {
		"bProcessing": true,
		"bServerSide": true,
		"sAjaxSource": "scripts/server_processing.php",
		"fnServerData": fnDataTablesPipeline
	} );
} );

Other examples