for simple search
on library.js locate this
oTable.fnSetFilteringDelay(350);
and replace it with this
oTable.fnFilterOnReturn();  
you will have to add the datatable function : fnFilterOnReturn()
located here
paste it either at the end of dataTables.fnSetFilteringDelay.js or somewhere that it can be called (maybe library.js)
this will enable you to search on the simple search by pressing the return key thus preventing multiple querys to be done on the database on every character typed. Alternatevely and more easily you can simply increase the timer to 5000 (5 seconds) on oTable.fnSetFilteringDelay(350); -> oTable.fnSetFilteringDelay(5000); without adding any function making the search with a 5 second delay.
---- Advanced search--
On advanced search I couldn't do something similar.
What I did though and it is a bit dirty is enabling the search when a '%' character inserted on the end of each string typed.
this will fire the search once for every string when the '%' inserted in a field instead of firing a query on every character typed.
in ibrary.js locate :
 else if (searchTermType === "n") {
                    regExpr = new RegExp(numericRegEx);
                    if (searchTerm[i].charAt(0) === "-") {
                        searchTerm[i] = searchTerm[i].substr(1);
                    }

under it add
else if (searchTermType == "s")
                {
                if (searchTerm[i].charAt(searchTerm[i].length - 1) !="%")
                  {allValid = false;}
                } 

'%' has to be added on the end of every string typed in order for the query to be fired
If anyone has a better solution please share.
This is a dirty hack not extensively tested. USE AT YOUR OWN RISK.