Find child records having specified parent guid

Hello,

I am using CRMRestKit and want to determine in front-end code number of child entities having a given parentid.

Example, entity A and B have 1:N relationship.

I have GUID of entity A and now need to find how many records of B are related to the GUID of A.

I searched and tried many things, but i am still unable to get it to work.

Here is my best shot :

var filter = "new_childPrimaryId/new_parentPrimartId eq 'Guid(" + knownParentGuid + ")' ";

        CrmRestKit.ByQuery('new_childSchemaName', [], filter, false).
        then(function (data, status, xhr) {
            //alert("results are" + data.d.results);
            var details = data.d.results;
        },
             function (xhr, status, errorThrown) {
            }
        );

new_childPrimaryId = "Name" of feild of child entity, not the 'schema name' or 'display name'.

new_parentPrimartId = lookup field name of parent in child entity. Again, it is the "Name" of the lookup

The solution lies somewhere in a correct filter.

Thanks