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Retrieving additional data


Retrieving additional data

The number of rows and columns retrieved with the first paint call is normally defined in initialProperties. But there are instances when this is not enough.

The maximum number of cells (qWidth * qHeight) allowed in an initial data fetch is 10,000. Retrieve additional data in chunks using the getData method in the Backend API.



var requestPage = [{
	qTop : lastrow + 1,
	qLeft : 0,
	qWidth : 10, //should be # of columns
	qHeight : Math.min(50, this.backendApi.getRowCount() - lastrow)
$element.find("#more").on("click", function() {
	self.backendApi.getData(requestPage).then(function(dataPages) {
Note: The call is asynchronous and returns a promise. You need to trigger the actual re-paint after the call has completed and you do this using the then() method.

Example: Retrieving additional data in chunks

In this example, the getData method will get the cells defined by requestPage and return the cells in the dataPages parameter. It will also update the layout buffer used by eachDataRow so when the paint function is called again, it will have all rows. This usage means the visualization will build up gradually.
paint: function ( $element ) {
     var lastrow = 0, me = this;
     //loop through the rows we have and render
     this.backendApi.eachDataRow( function ( rownum, row ) {
                lastrow = rownum;
                //do something with the row..
     if(this.backendApi.getRowCount() > lastrow +1){
             //we havent got all the rows yet, so get some more, 1000 rows
              var requestPage = [{
                    qTop: lastrow + 1,
                    qLeft: 0,
                    qWidth: 10, //should be # of columns
                    qHeight: Math.min( 1000, this.backendApi.getRowCount() - lastrow )
               this.backendApi.getData( requestPage ).then( function ( dataPages ) {
                        //when we get the result trigger paint again
                        me.paint( $element );
               } );