[CASSANDRA-13657] Materialized Views: Index MV on TTL'ed column produces orphanized view entry if another column keeps entry live

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Duplicate
• Component/s: Feature/Materialized Views
• Labels: materializedviews ttl
• Severity: Normal
• Assignee: Krishna Dattu Koneru
• Reporter: Fridtjof Sander

Authors

Krishna Dattu Koneru

• Created: 03/Jul/17 10:32
• Updated: 16/Apr/19 09:30
• Resolved: 05/Sep/17 07:58

Description

CREATE TABLE t (k int, a int, b int, PRIMARY KEY (k));
CREATE MATERIALIZED VIEW mv AS SELECT * FROM t WHERE k IS NOT NULL AND a IS NOT NULL PRIMARY KEY (a, k);
INSERT INTO t (k) VALUES (1);
UPDATE t USING TTL 5 SET a = 10 WHERE k = 1;
UPDATE t SET b = 100 WHERE k = 1;
SELECT * from t; SELECT * from mv;

 k | a  | b
---+----+-----
 1 | 10 | 100

(1 rows)

 a  | k | b
----+---+-----
 10 | 1 | 100

(1 rows)

-- 5 seconds later

SELECT * from t; SELECT * from mv;

 k | a    | b
---+------+-----
 1 | null | 100

(1 rows)

 a  | k | b
----+---+-----
 10 | 1 | 100

(1 rows)

-- that view entry's liveness-info is (probably) dead, but the entry is kept alive by b=100

DELETE b FROM t WHERE k=1;
SELECT * from t; SELECT * from mv;

 k | a    | b
---+------+------
 1 | null | null

(1 rows)

 a  | k | b
----+---+-----
 10 | 1 | 100

(1 rows)

DELETE FROM t WHERE k=1;
cqlsh:test> SELECT * from t; SELECT * from mv;

 k | a | b
---+---+---

(0 rows)

 a  | k | b
----+---+-----
 10 | 1 | 100

(1 rows)

-- deleting the base-entry doesn't help, because the view-key can not be constructed anymore (a=10 already expired)

The problem here is that although the view-entry's liveness-info (probably) expired correctly a regular column (`b`) keeps the view-entry live. It should have disappeared since it's indexed column (`a`) expired in the corresponding base-row. This is pretty severe, since that view-entry is now orphanized.

Issue Links

• relates to: CASSANDRA-11500 Obsolete MV entry may not be properly deleted