From 241f2078ed3f9dfd1f422088b530338ec31b226b 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
---
 .../org/apache/cassandra/db/LivenessInfo.java | 12 ++--
 .../cassandra/db/ReusableLivenessInfo.java    |  6 ++
 .../cassandra/cql3/ViewCompactionTest.java    | 65 +++++++++++++++++++
 3 files changed, 78 insertions(+), 5 deletions(-)
 create mode 100644 test/unit/org/apache/cassandra/cql3/ViewCompactionTest.java

diff --git a/src/java/org/apache/cassandra/db/LivenessInfo.java b/src/java/org/apache/cassandra/db/LivenessInfo.java
index e72c408d1ecd..22865b325bef 100644
--- a/src/java/org/apache/cassandra/db/LivenessInfo.java
+++ b/src/java/org/apache/cassandra/db/LivenessInfo.java
@@ -211,11 +211,7 @@ default boolean supersedes(LivenessInfo other)
         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 boolean isLive(long nowInSec)
             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 b3c34eac0132..1bc2b5cb4f85 100644
--- a/src/java/org/apache/cassandra/db/ReusableLivenessInfo.java
+++ b/src/java/org/apache/cassandra/db/ReusableLivenessInfo.java
@@ -49,6 +49,12 @@ public boolean isExpiring()
         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 000000000000..a1b5fc4b0c75
--- /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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