Cassandra Delete query with If condition not working - cassandra

Question

I've got a cassandra table and want to delete a row, but only if one column has one specific value.
Even if cassandra claims that deleting succeeded (it returned "applied: true") the message will still be present.
Let's create the table and insert some data:
CREATE TABLE IF NOT EXISTS test
(
id uuid PRIMARY KEY,
recipient text,
message text
);
INSERT INTO test (id, recipient, message)
VALUES (7ee055ee-b5dd-4bfd-b184-614d51e268d5, 'felix', 'foo');
INSERT INTO test (id, recipient, message)
VALUES (86c9d632-dc24-4635-8277-c987c78bd242, 'andrew', 'bar');
Now I want to delete one message, but only if the user who requests the deletion (in this case felix) is the recipient and thus has permissions to do so:
cqlsh:service_message> DELETE FROM test WHERE id=7ee055ee-b5dd-4bfd-b184-614d51e268d5 IF recipient='felix';
[applied]
-----------
True
So I would now think that the query did succeed, but if we have a look at the table we'll see that the message still exists.
cqlsh:service_message> SELECT * FROM test;
id | message | recipient
--------------------------------------+---------+-----------
86c9d632-dc24-4635-8277-c987c78bd242 | bar | andrew
7ee055ee-b5dd-4bfd-b184-614d51e268d5 | foo | felix
(2 rows)
Some additional information:
cqlsh 5.0.1 | Cassandra 3.11.2 | CQL spec 3.4.4 | Native protocol v4
cqlsh> DESCRIBE KEYSPACE service_message
CREATE KEYSPACE service_message WITH replication = {'class': 'SimpleStrategy', 'replication_factor': '3'} AND durable_writes = true;
CREATE TABLE service_message.test (
id uuid PRIMARY KEY,
message text,
recipient text
) WITH bloom_filter_fp_chance = 0.01
AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
AND comment = ''
AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'}
AND compression = {'chunk_length_in_kb': '64', 'class': 'org.apache.cassandra.io.compress.LZ4Compressor'}
AND crc_check_chance = 1.0
AND dclocal_read_repair_chance = 0.1
AND default_time_to_live = 0
AND gc_grace_seconds = 864000
AND max_index_interval = 2048
AND memtable_flush_period_in_ms = 0
AND min_index_interval = 128
AND read_repair_chance = 0.0
AND speculative_retry = '99PERCENTILE';

Answer 1

INSERT and UPDATE statements using the IF clause support lightweight transactions .
From Datastax docs on CQL: https://docs.datastax.com/en/cql/3.3/cql/cql_using/useInsertLWT.html
I'm pretty sure deletes are not supported. If you want to effectively delete your information, you may consider setting the values of the cells in an UPDATE statement to null. Either by delete or by setting nulls, you are still creating tombstones.