Does Cassandra Insert JSON creates Tombstones?

I am using Cassandra's insert JSON feature to insert data into the table. In the JSON that I create, I do not include the null values. Meaning, ignore the fields that have null values in it.

Does Cassandra create tombstones in such cases, if I am inserting the record say, for the first time?

I assume for subsequent upsert for the same key will create tombstone. Is that right?

Cell tombstone should still get created for the values which are not included in the json you are trying to insert.

Consider a table called cyclist having id, first name and last name. We will insert a row using a json string which contains only last name.

CREATE KEYSPACE IF NOT EXISTS cycling WITH REPLICATION = { 'class' : 'NetworkTopologyStrategy', 'datacenter1' : 3 };

CREATE TABLE cycling.cyclist ( id UUID PRIMARY KEY, first_name text, last_name text );

CREATE TABLE cycling.cyclist ( id UUID PRIMARY KEY, first_name text, last_name text );

INSERT INTO cycling.cyclist JSON '{"id" : "829aa84a-4bba-411f-a4fb-38167a987cda", "last_name" : "MYLASTNAME" }';

Now if we look at the data structure within sstable, it looks like below.

[
  {
    "partition" : {
      "key" : [ "829aa84a-4bba-411f-a4fb-38167a987cda" ],
      "position" : 0
    },
    "rows" : [
      {
        "type" : "row",
        "position" : 30,
        "liveness_info" : { "tstamp" : "2020-05-13T07:10:59.298374Z" },
        "cells" : [
          { "name" : "first_name", "deletion_info" : { "local_delete_time" : "2020-05-13T07:10:59Z" }
          },
          { "name" : "last_name", "value" : "MYLASTNAME" }
        ]
      }
    ]
  }
]

Observe the cell tombstone created for first_name.

This is different than the sstable structure when we insert the data using selective fields.

INSERT INTO cycling.cyclist(id, first_name) VALUES ( 'c49d1614-e841-4bd4-993b-02d49ae7414c', 'MYFIRSTNAME');

Now look at the sstable structure

[
  {
    "partition" : {
      "key" : [ "829aa84a-4bba-411f-a4fb-38167a987cda" ],
      "position" : 0
    },
    "rows" : [
      {
        "type" : "row",
        "position" : 30,
        "liveness_info" : { "tstamp" : "2020-05-13T07:10:59.298374Z" },
        "cells" : [
          { "name" : "first_name", "deletion_info" : { "local_delete_time" : "2020-05-13T07:10:59Z" }
          },
          { "name" : "last_name", "value" : "MYLASTNAME" }
        ]
      }
    ]
  },
  {
    "partition" : {
      "key" : [ "c49d1614-e841-4bd4-993b-02d49ae7414c" ],
      "position" : 47
    },
    "rows" : [
      {
        "type" : "row",
        "position" : 77,
        "liveness_info" : { "tstamp" : "2020-05-13T07:23:42.964609Z" },
        "cells" : [
          { "name" : "first_name", "value" : "MYFIRSTNAME" }
        ]
      }
    ]
  }
]