From 1a9ab95c203c511ba13c209768f08d887602ed2e Mon Sep 17 00:00:00 2001
From: Dmitry Konstantinov <netudima@gmail.com>
Date: Sun, 29 Mar 2026 17:30:53 +0100
Subject: [PATCH] Fix a removed TTLed row re-appearance in a materialized view
 after a cursor compaction

Add an implementation of isExpired to ReusableLivenessInfo, before the change the method implementation was interited from an interface and always returned false, so livenessInfo().supersedes(...) did not work properly.

patch by Dmitry Konstantinov; reviewed by Branimir Lambov, Nitsan Wakart for CASSANDRA-21152
---
 CHANGES.txt                                   |  1 +
 .../org/apache/cassandra/db/LivenessInfo.java | 12 ++--
 .../cassandra/db/ReusableLivenessInfo.java    |  6 ++
 .../cassandra/cql3/ViewCompactionTest.java    | 65 +++++++++++++++++++
 4 files changed, 79 insertions(+), 5 deletions(-)
 create mode 100644 test/unit/org/apache/cassandra/cql3/ViewCompactionTest.java

diff --git a/CHANGES.txt b/CHANGES.txt
index a1fd10795c..f76adf7e41 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,4 +1,5 @@
 6.0-alpha1
+ * Fix a removed TTLed row re-appearance in a materialized view after a cursor compaction (CASSANDRA-21152)
  * Rework ZSTD dictionary compression logic to create a trainer per training (CASSANDRA-21209)
  * Improve performance when calculating settled placements during range movements (CASSANDRA-21144)
  * Make shadow gossip round parameters configurable for testing (CASSANDRA-21149)
diff --git a/src/java/org/apache/cassandra/db/LivenessInfo.java b/src/java/org/apache/cassandra/db/LivenessInfo.java
index e72c408d1e..22865b325b 100644
--- a/src/java/org/apache/cassandra/db/LivenessInfo.java
+++ b/src/java/org/apache/cassandra/db/LivenessInfo.java
@@ -211,11 +211,7 @@ public interface LivenessInfo extends IMeasurableMemory
         return isExpiring();
     }
 
-    default boolean isExpired()
-    {
-        return false;
-    }
-
+    boolean isExpired();
     /**
      * Returns a copy of this liveness info updated with the provided timestamp.
      *
@@ -404,6 +400,12 @@ public interface LivenessInfo extends IMeasurableMemory
             return !isEmpty();
         }
 
+        @Override
+        public boolean isExpired()
+        {
+            return false;
+        }
+
         @Override
         public String toString()
         {
diff --git a/src/java/org/apache/cassandra/db/ReusableLivenessInfo.java b/src/java/org/apache/cassandra/db/ReusableLivenessInfo.java
index b3c34eac01..1bc2b5cb4f 100644
--- a/src/java/org/apache/cassandra/db/ReusableLivenessInfo.java
+++ b/src/java/org/apache/cassandra/db/ReusableLivenessInfo.java
@@ -49,6 +49,12 @@ public class ReusableLivenessInfo implements LivenessInfo
         return localExpirationTime != NO_EXPIRATION_TIME;
     }
 
+    @Override
+    public boolean isExpired()
+    {
+        return ttl == EXPIRED_LIVENESS_TTL;
+    }
+
     /**
      * {@link org.apache.cassandra.db.rows.AbstractCell#isTombstone()}
      */
diff --git a/test/unit/org/apache/cassandra/cql3/ViewCompactionTest.java b/test/unit/org/apache/cassandra/cql3/ViewCompactionTest.java
new file mode 100644
index 0000000000..a1b5fc4b0c
--- /dev/null
+++ b/test/unit/org/apache/cassandra/cql3/ViewCompactionTest.java
@@ -0,0 +1,65 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.cassandra.cql3;
+
+import java.util.Collections;
+
+import org.junit.Test;
+
+import org.apache.cassandra.Util;
+import org.apache.cassandra.db.ColumnFamilyStore;
+import org.apache.cassandra.db.Keyspace;
+
+public class ViewCompactionTest extends ViewAbstractTest
+{
+
+    @Test
+    public void testCompactionOfDeletedRowWithTtl() throws Throwable
+    {
+        createTable("CREATE TABLE %s (k int, a int, b int, c int, primary key(k, a)) with default_time_to_live=6000");
+        createView("CREATE MATERIALIZED VIEW %s AS SELECT k,a,b FROM %s WHERE k IS NOT NULL AND a IS NOT NULL PRIMARY KEY (a, k)");
+
+        execute("UPDATE %s SET c=2 WHERE k=1 AND a=1");
+        flushView();
+        assertRows(execute("SELECT k,a,b,c FROM %s"), row(1, 1, null, 2));
+        assertRows(executeView("SELECT k,a,b FROM %s"), row(1, 1, null));
+
+        compact(keyspace(), currentView());
+
+        assertRows(execute("SELECT k,a,b,c FROM %s"), row(1, 1, null, 2));
+        assertRows(executeView("SELECT k,a,b FROM %s"), row(1, 1, null));
+
+        execute("DELETE c FROM %s WHERE k=1 AND a=1");
+        flushView();
+
+        assertRows(execute("SELECT k,a,b,c FROM %s"), Collections.emptyList());
+        assertRows(executeView("SELECT k,a,b FROM %s"), Collections.emptyList());
+
+        compact(keyspace(), currentView());
+
+        assertRows(execute("SELECT k,a,b,c FROM %s"), Collections.emptyList());
+        assertRows(executeView("SELECT k,a,b FROM %s"), Collections.emptyList());
+    }
+
+    private void flushView()
+    {
+        ColumnFamilyStore cfs = Keyspace.open(keyspace()).getColumnFamilyStore(currentView());
+        Util.flush(cfs);
+    }
+}
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