I found that the 'postData' is cached in jqgrid? Is that normal? e.g.

$("#grid").setGridParam({postData: {a:'aaa', b:'bbb'}).trigger("reloadGrid");

The http request would have param a=aaa&b=bbb

$("#grid").setGridParam({postData: {c:'ccc'}).trigger("reloadGrid");

The http request would have param a=aaa&b=bbb&c=ccc

Currently, I would like to have 'clean' postData every time, so I do

$("#grid").setGridParam({postData: null}).setGridParam({postData:freshDataToPost}).trigger("reloadGrid");

Is this the proper way?