[CASSANDRA-16671] Cassandra can return no row when the row columns have been deleted. - ASF JIRA

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Details

Type: Bug
Status: Resolved
Priority: Normal
Resolution: Fixed
Fix Version/s: 3.0.25, 3.11.11, 4.0-rc2, 4.0
Component/s: Legacy/Local Write-Read Paths
Labels:
None

Bug Category:
Correctness
Severity:
Normal
Complexity:
Normal
Discovered By:
Code Inspection
Platform:

All
Impacts:

None
Since Version:

3.11.10
Source Control Link:

https://github.com/apache/cassandra/commit/24346d17899df8610a5f425c7074ddd5dc8082bb
Test and Documentation Plan:

Hide

The patches add several extra unit tests and in-jvm dtests

Show
The patches add several extra unit tests and in-jvm dtests

Description

It is the semantic of CQL that a (CQL) row exists as long as it has one non-null column (including the PK columns).

To determine if a row has some non-null primary key, Cassandra relies on the row primary key liveness.

For example:

CREATE TABLE test (pk int, ck int, v int, PRIMARY KEY(pk, ck));
INSERT INTO test(pk, ck, v) VALUES (1, 1, 1);
DELETE v FROM test WHERE pk = 1 AND ck = 1
SELECT v FROM test;

will return

v
---
null

UPDATE statements do not set the row primary key liveness by consequence if the user had used an UPDATE statement instead of an INSERT the SELECT query would not have returned any rows.

~~CASSANDRA-16226~~ introduced a regression by stopping early in the timestamp ordered logic if an UPDATE statement covering all the columns was found in an SSTable. As the row returned did not have a primary key liveness if another node was also returning a column deletion, the expected row will not be returned.

The problem can be reproduced with the following test:

   @Test
    public void testSelectWithUpdatedColumnOnOneNodeAndColumnDeletionOnTheOther() throws Throwable
    {
        try (Cluster cluster = init(builder().withNodes(2).start()))
        {
            cluster.schemaChange(withKeyspace("CREATE TABLE %s.tbl (pk int, ck text, v int, PRIMARY KEY (pk, ck))"));
            cluster.get(1).executeInternal(withKeyspace("INSERT INTO %s.tbl (pk, ck, v) VALUES (1, '1', 1) USING TIMESTAMP 1000"));
            cluster.get(1).flush(KEYSPACE);
            cluster.get(1).executeInternal(withKeyspace("UPDATE %s.tbl USING TIMESTAMP 2000 SET v = 2 WHERE pk = 1 AND ck = '1'"));
            cluster.get(1).flush(KEYSPACE);

            cluster.get(2).executeInternal(withKeyspace("DELETE v FROM %s.tbl USING TIMESTAMP 3000 WHERE pk=1 AND ck='1'"));
            cluster.get(2).flush(KEYSPACE);

            assertRows(cluster.coordinator(2).execute(withKeyspace("SELECT * FROM %s.tbl WHERE pk=1 AND ck='1'"), ConsistencyLevel.ALL),
                       row(1, "1", null)); // <-- FAIL
            assertRows(cluster.coordinator(2).execute(withKeyspace("SELECT v FROM %s.tbl WHERE pk=1 AND ck='1'"), ConsistencyLevel.ALL),
                       row((Integer) null));

        }
    }