When I do a table repair, I see a lot of warnings like the following:
WARN [CompactionExecutor:112958] 2016-04-07 15:39:33,160 SliceQueryFilter.java:236 - Read 10002 live and 2857 tombstoned cells
But I do not delete anything and do not set TTLs, so nothing has been deleted. Why are there so many tombstones? The datasize is about 200G, but I have inserted some cells with NULL.
I had the same issue recently. And the reason was that I was inserting NULL values. I just did not know that I did.
If you use a prepared statement and you do not set some of the parameters, or you set them to NULL, or if you insert a JSON object that does not contain a key for every column of the table, then you end up with a tombstone for each of those columns.
In case of the prepared statement you can avoid the tombstone by explicitly setting unused parameters as unset. See CASSANDRA-7304.
Unfortunately there is no such syntax/API for JSON inserts yet. Have a look at CASSANDRA-11424 to check the progress.
