If no records are specified in the set then nothing will be updated. To update a record use action:"update". To remove a record use action:"remove". To add a record use action:"add". Different actions can be used within the same set. For example:
"set": [
{
"action": "update",
...........
},
{
"action": "remove",
...........
},
{
"action": "add",
...........
}
]