hudi-agent commented on code in PR #19081:
URL: https://github.com/apache/hudi/pull/19081#discussion_r3823634853


##########
hudi-client/hudi-client-common/src/main/java/org/apache/hudi/table/action/ttl/strategy/KeepByEventTimeStrategy.java:
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@@ -0,0 +1,351 @@
+/*
+ * 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.hudi.table.action.ttl.strategy;
+
+import org.apache.hudi.common.table.timeline.HoodieInstantTimeGenerator;
+import org.apache.hudi.common.util.PartitionPathEncodeUtils;
+import org.apache.hudi.common.util.collection.Pair;
+import org.apache.hudi.config.HoodieTTLConfig;
+import org.apache.hudi.keygen.constant.KeyGeneratorOptions;
+import org.apache.hudi.table.HoodieTable;
+
+import lombok.extern.slf4j.Slf4j;
+
+import java.text.ParseException;
+import java.time.DateTimeException;
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.ZoneOffset;
+import java.time.format.DateTimeFormatter;
+import java.time.format.DateTimeParseException;
+import java.time.temporal.TemporalAccessor;
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Event-time based partition TTL strategy: lifetime is read from the 
partition path, not from
+ * commit metadata. Late-arriving writes into an old partition do not extend 
its lifetime, and
+ * backfilled historic partitions are still considered old. Compare with 
{@link KeepByTimeStrategy}
+ * (last commit time) and {@link KeepByCreationTimeStrategy} (creation commit 
time).
+ *
+ * <h3>Supported path shapes</h3>
+ * The first-class, tested shapes are day and hour granularity. Each example 
shows the partition
+ * path on the left and the required {@code timeSegStartIndex} on the right 
(see
+ * <i>Locating the time block</i> below); non-time segments may appear before 
and/or after the
+ * time block.
+ * <ul>
+ *   <li>Day, {@code format=yyyy-MM-dd}
+ *     <ul>
+ *       <li>time only: {@code 2026-06-27}, {@code dt=2026-06-27} — 
timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time: {@code region=us/2026-06-27}, {@code 
region=us/dt=2026-06-27} — timeSegStartIndex {@code 1}</li>
+ *       <li>time + suffix: {@code 2026-06-27/source=app}, {@code 
dt=2026-06-27/source=app} — timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time + suffix: {@code 
region=us/dt=2026-06-27/source=app} — timeSegStartIndex {@code 1}</li>
+ *     </ul>
+ *   </li>
+ *   <li>Day, {@code format=yyyyMMdd}
+ *     <ul>
+ *       <li>time only: {@code 20260627}, {@code dt=20260627} — 
timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time: {@code region=us/20260627}, {@code 
region=us/dt=20260627} — timeSegStartIndex {@code 1}</li>
+ *       <li>time + suffix: {@code 20260627/source=app}, {@code 
dt=20260627/source=app} — timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time + suffix: {@code region=us/dt=20260627/source=app} 
— timeSegStartIndex {@code 1}</li>
+ *     </ul>
+ *   </li>
+ *   <li>Hour, {@code format=yyyy-MM-dd/HH}
+ *     <ul>
+ *       <li>time only: {@code 2026-06-27/12}, {@code dt=2026-06-27/hh=12} — 
timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time: {@code region=us/2026-06-27/12}, {@code 
region=us/dt=2026-06-27/hh=12} — timeSegStartIndex {@code 1}</li>
+ *       <li>time + suffix: {@code 2026-06-27/12/source=app}, {@code 
dt=2026-06-27/hh=12/source=app} — timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time + suffix: {@code 
region=us/dt=2026-06-27/hh=12/source=app} — timeSegStartIndex {@code 1}</li>
+ *     </ul>
+ *   </li>
+ *   <li>Hour, {@code format=yyyyMMdd/HH}
+ *     <ul>
+ *       <li>time only: {@code 20260627/12}, {@code dt=20260627/hh=12} — 
timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time: {@code region=us/20260627/12}, {@code 
region=us/dt=20260627/hh=12} — timeSegStartIndex {@code 1}</li>
+ *       <li>time + suffix: {@code 20260627/12/source=app}, {@code 
dt=20260627/hh=12/source=app} — timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time + suffix: {@code 
region=us/dt=20260627/hh=12/source=app} — timeSegStartIndex {@code 1}</li>
+ *     </ul>
+ *   </li>
+ * </ul>
+ * Hive-style key names are not constrained: {@code dt=}, {@code day=}, {@code 
event_date=},
+ * {@code hh=}, {@code hour=} all work; only the value after {@code =} is 
parsed.
+ * <p>
+ * Any {@link java.time.format.DateTimeFormatter} pattern works as long as the 
resulting
+ * {@link java.time.temporal.TemporalAccessor} can be resolved to either an 
{@link java.time.Instant}
+ * or a {@link java.time.LocalDate} (day-only patterns are anchored at UTC 
start-of-day). A
+ * {@code /} in the pattern means the time value spans that many consecutive 
path segments.
+ * Patterns missing day-of-month, e.g. month-only {@code yyyy-MM}, cannot be 
resolved and will
+ * raise the standard parse-failure error at runtime.
+ *
+ * <h3>Locating the time block</h3>
+ * The time block must occupy a <i>contiguous</i> segment range of the 
partition path. Only the
+ * segments before it count toward {@code timeSegStartIndex}; segments after 
are ignored. Interleaved
+ * layouts such as {@code dt=20260627/source=app/hh=12} are not supported -- 
the time block must
+ * be in one piece.
+ *
+ * <h3>Time zone</h3>
+ * Both the partition's event time and the cutoff derived from {@code 
instantTime} are interpreted
+ * in UTC. Set {@code hoodie.table.timeline.timezone=UTC} so the timeline 
writes instants under the
+ * same convention; otherwise the cutoff drifts by the JVM's UTC offset -- a 
boundary effect at
+ * day granularity, a full-offset shift at hour granularity.
+ *
+ * <h3>Configuration</h3>
+ * All three knobs come with defaults, so a table whose partition path is 
purely a date in
+ * {@code yyyy-MM-dd} form works out of the box.
+ * <ul>
+ *   <li>{@link org.apache.hudi.config.HoodieTTLConfig#EVENT_TIME_FORMAT} — 
date-time pattern of
+ *       the time block in the partition path. Default {@code yyyy-MM-dd}. A 
{@code /} in the
+ *       pattern means the time block spans that many consecutive 
segments.</li>
+ *   <li>{@link 
org.apache.hudi.config.HoodieTTLConfig#EVENT_TIME_SEGMENT_START_INDEX} —
+ *       0-based index of the first segment that carries the time block. 
Default {@code 0}.
+ *       Raise it when non-time segments come before the time block (see 
examples above).</li>
+ *   <li>{@link 
org.apache.hudi.config.HoodieTTLConfig#EVENT_TIME_DELETE_HIVE_DEFAULT_PARTITION}
 —
+ *       whether to treat partitions whose time block contains {@code 
__HIVE_DEFAULT_PARTITION__}
+ *       in <i>any</i> segment as expired. Such a partition has an undefined 
event time (one of
+ *       its event-time columns was {@code NULL}, so the row cannot be placed 
on the configured
+ *       time axis) and falls outside the normal cutoff comparison. Default 
{@code false}, i.e.
+ *       such partitions are skipped with a WARN and the user keeps explicit 
control over them.
+ *       Applies to both single-segment formats (e.g. {@code 
dt=__HIVE_DEFAULT_PARTITION__}) and
+ *       multi-segment ones (e.g. {@code 
dt=2026-06-28/hh=__HIVE_DEFAULT_PARTITION__}).</li>
+ * </ul>
+ */
+@Slf4j
+public class KeepByEventTimeStrategy extends KeepByTimeStrategy {
+
+  private final String eventTimeFormat;
+  private final int timeSegStartIndex;
+  private final boolean shouldDeleteHiveDefaultPartition;
+  private final boolean hiveStylePartitioning;
+
+  public KeepByEventTimeStrategy(HoodieTable hoodieTable, String instantTime) {
+    super(hoodieTable, instantTime);
+    // Defaults: format='yyyy-MM-dd', timeSegStartIndex=0, 
deleteHiveDefaultPartition=false. The
+    // two guards below catch users who set the values explicitly to 
obviously-broken inputs.
+    this.eventTimeFormat = writeConfig.getPartitionTTLEventTimeFormat();
+    if (eventTimeFormat == null || eventTimeFormat.isEmpty()) {
+      throw new IllegalArgumentException(
+          HoodieTTLConfig.EVENT_TIME_FORMAT.key() + " must not be empty.");
+    }
+    this.timeSegStartIndex = 
writeConfig.getPartitionTTLEventTimeSegmentStartIndex();
+    if (timeSegStartIndex < 0) {
+      throw new IllegalArgumentException(
+          HoodieTTLConfig.EVENT_TIME_SEGMENT_START_INDEX.key() + " must be >= 
0, got " + timeSegStartIndex);
+    }
+    this.shouldDeleteHiveDefaultPartition = 
writeConfig.shouldPartitionTTLEventTimeDeleteHiveDefaultPartition();
+    // Hive-style partitioning is a table-level property recorded at table 
creation; trust it
+    // rather than guessing per-segment from a stray '=' character in a value.
+    this.hiveStylePartitioning = Boolean.parseBoolean(
+        
hoodieTable.getMetaClient().getTableConfig().getHiveStylePartitioningEnable());
+  }
+
+  @Override
+  protected List<String> getExpiredPartitionsForTimeStrategy(List<String> 
partitionPathsForTTL) {
+    long cutoffMillis = resolveCutoffMillis(instantTime, ttlInMilis);
+    DateTimeFormatter formatter = 
DateTimeFormatter.ofPattern(eventTimeFormat).withZone(ZoneOffset.UTC);
+    int segCount = segmentCount(eventTimeFormat);
+
+    // Step 1: filter by event time. Pure computation over immutable inputs 
(no shared state, no
+    // I/O), so a raw parallel stream on the common ForkJoinPool is safe. In a 
healthy table the
+    // vast majority of partitions survive this filter, so most of the work 
stays here and never
+    // reaches the more expensive step 2.
+    List<String> eventTimeExpired = partitionPathsForTTL.stream().parallel()
+        .filter(path -> isPartitionExpiredByEventTime(
+            path, formatter, timeSegStartIndex, segCount, cutoffMillis,
+            shouldDeleteHiveDefaultPartition, hiveStylePartitioning))
+        .collect(Collectors.toList());
+    if (eventTimeExpired.isEmpty()) {
+      return Collections.emptyList();
+    }
+
+    // Step 2: drop partitions that an earlier TTL replace already emptied. 
Their event time is
+    // derived from the (unchanged) path, so without this filter they would be 
re-selected on
+    // every batch -- issuing an empty replace commit each time and never 
converging. Keep only
+    // partitions that still have a live file slice, mirroring 
KeepByTimeStrategy which keys off
+    // the surviving slices' last commit time and thus naturally skips deleted 
ones.
+    //
+    // hasLiveFileSlice touches hoodieTable.getHoodieView(), which for 
non-default view types
+    // (SPILLABLE_DISK, EMBEDDED_KV_STORE) mutates a backing store during 
first-time partition
+    // load under a shared read lock -- unsafe under unbounded concurrent 
access on the common
+    // ForkJoinPool. Route the lookup through the engine context with bounded 
parallelism, the
+    // same pattern KeepByTimeStrategy#getLastCommitTimeForPartitions uses, so 
that blocking file
+    // listings don't run on the common pool and respect 
getPartitionTTLStatsMaxParallelism.
+    int statsParallelism = Math.min(eventTimeExpired.size(), 
writeConfig.getPartitionTTLStatsMaxParallelism());
+    return hoodieTable.getContext().map(eventTimeExpired,
+        partitionPath -> Pair.of(partitionPath, 
hasLiveFileSlice(partitionPath)),
+        statsParallelism).stream()
+        .filter(Pair::getRight)
+        .map(Pair::getLeft)
+        .collect(Collectors.toList());
+  }
+
+  /**
+   * Whether the partition still has at least one live file slice as of {@code 
instantTime}.
+   * File groups replaced by an earlier TTL delete are excluded by the file 
system view, so an
+   * already-deleted partition returns {@code false} here even while its 
directory lingers on
+   * storage awaiting the cleaner.
+   */
+  private boolean hasLiveFileSlice(String partitionPath) {
+    return hoodieTable.getHoodieView()
+        .getLatestFileSlicesBeforeOrOn(partitionPath, instantTime, true)
+        .findAny()
+        .isPresent();
+  }
+
+  /**
+   * Number of '/'-separated path segments the configured format occupies.
+   * Example: {@code yyyy-MM-dd/HH} -> 2.
+   */
+  static int segmentCount(String format) {
+    return format.split("/").length;
+  }
+
+  /**
+   * Resolve the "now" reference timestamp from {@code instantTime}, in UTC.
+   * <p>
+   * Anchoring on {@code instantTime} keeps the strategy idempotent across 
retries of the same
+   * replace commit. We parse it in UTC so the cutoff and the partition's 
event time (also parsed
+   * in UTC above) sit on the same axis -- otherwise expiry drifts by the 
JVM's UTC offset, which
+   * is negligible at day granularity but a full-offset shift at hour 
granularity.
+   */
+  static long resolveCutoffMillis(String instantTime, long ttlInMillis) {
+    try {
+      return HoodieInstantTimeGenerator.parseDateFromInstantTime(instantTime, 
ZoneOffset.UTC).getTime() - ttlInMillis;
+    } catch (ParseException e) {
+      throw new IllegalStateException("Failed to parse instant time " + 
instantTime, e);
+    }
+  }
+
+  /**
+   * Decide whether a partition path is expired.
+   * <p>
+   * The strategy treats any partition that cannot be parsed under the 
configured format /
+   * start-index / hive-style as a hard error. Reasoning: this class derives 
lifetime from the
+   * path itself, so a partition we cannot parse has no defined lifetime, and 
silently skipping
+   * it would leave it in the table forever while the rest of TTL appears to 
succeed. Switch to
+   * {@code KEEP_BY_TIME} or {@code KEEP_BY_CREATION_TIME} (which key off 
commit metadata, not
+   * the path) if the table contains partitions that don't conform to a single 
event-time shape.
+   * <p>
+   * Package-private so unit tests can exercise it directly without spinning 
up a HoodieTable.
+   * <p>
+   * Note the two trailing {@code boolean} flags are easy to transpose at call 
sites; keep them in
+   * this order: {@code deleteHiveDefaultPartition} first, {@code 
hiveStylePartitioning} last.
+   *
+   * @param partitionPath              the partition path to evaluate
+   * @param formatter                  formatter built from the configured 
event-time format
+   * @param timeSegStartIndex          0-based index of the first segment 
carrying the time block
+   * @param segCount                   number of segments the time block spans
+   * @param cutoffMillis               partitions with event time strictly 
before this are expired
+   * @param deleteHiveDefaultPartition treat a time block containing the Hive 
default marker as expired
+   * @param hiveStylePartitioning      whether segments carry a {@code 
field=value} prefix to strip
+   */
+  static boolean isPartitionExpiredByEventTime(String partitionPath,
+                                               DateTimeFormatter formatter,
+                                               int timeSegStartIndex,
+                                               int segCount,
+                                               long cutoffMillis,
+                                               boolean 
deleteHiveDefaultPartition,
+                                               boolean hiveStylePartitioning) {
+    String[] segments = partitionPath.split("/");
+    if (segments.length < timeSegStartIndex + segCount) {
+      throw new IllegalArgumentException(String.format(
+          "Partition '%s' has %d segment(s) but the configured event time 
spans %d segment(s) starting at index %d. "
+              + "Check %s and %s, "
+              + "or switch to KEEP_BY_TIME / KEEP_BY_CREATION_TIME if not all 
partitions of this table follow an event-time shape.",
+          partitionPath, segments.length, segCount, timeSegStartIndex,
+          HoodieTTLConfig.EVENT_TIME_FORMAT.key(), 
HoodieTTLConfig.EVENT_TIME_SEGMENT_START_INDEX.key()));
+    }
+
+    String[] timeSegs = new String[segCount];
+    boolean hasDefaultSegment = false;
+    for (int i = 0; i < segCount; i++) {
+      String seg = segments[timeSegStartIndex + i];
+      if (hiveStylePartitioning) {
+        int eq = seg.indexOf('=');
+        if (eq < 0) {
+          throw new IllegalArgumentException(String.format(
+              "Partition '%s' segment '%s' has no hive-style 'field=value' 
prefix but "
+                  + "%s=true on the table. "
+                  + "Switch to KEEP_BY_TIME / KEEP_BY_CREATION_TIME if such 
legacy partitions must coexist.",
+              partitionPath, seg, 
KeyGeneratorOptions.HIVE_STYLE_PARTITIONING_ENABLE.key()));
+        }
+        timeSegs[i] = seg.substring(eq + 1);
+      } else {
+        timeSegs[i] = seg;
+      }
+      if (PartitionPathEncodeUtils.DEFAULT_PARTITION_PATH.equals(timeSegs[i])) 
{

Review Comment:
   🤖 Hudi's canonical `PartitionPathParser.parseValue` (and `Type`) treat both 
`DEFAULT_PARTITION_PATH` and `DEPRECATED_DEFAULT_PARTITION_PATH` (`"default"`) 
as the null marker, but this only matches the former. On a legacy table whose 
null partition is encoded as `dt=default`, `hasDefaultSegment` stays false, 
`parseEventMillis("default", ...)` fails, and the throw a few lines below 
aborts the entire TTL run every batch. Should this also check the deprecated 
marker so those partitions get the same graceful skip?
   
   <sub><i>⚠️ AI-generated; verify before applying. React 👍/👎 to flag 
quality.</i></sub>



##########
hudi-client/hudi-client-common/src/main/java/org/apache/hudi/table/action/ttl/strategy/KeepByEventTimeStrategy.java:
##########
@@ -0,0 +1,351 @@
+/*
+ * 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.hudi.table.action.ttl.strategy;
+
+import org.apache.hudi.common.table.timeline.HoodieInstantTimeGenerator;
+import org.apache.hudi.common.util.PartitionPathEncodeUtils;
+import org.apache.hudi.common.util.collection.Pair;
+import org.apache.hudi.config.HoodieTTLConfig;
+import org.apache.hudi.keygen.constant.KeyGeneratorOptions;
+import org.apache.hudi.table.HoodieTable;
+
+import lombok.extern.slf4j.Slf4j;
+
+import java.text.ParseException;
+import java.time.DateTimeException;
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.ZoneOffset;
+import java.time.format.DateTimeFormatter;
+import java.time.format.DateTimeParseException;
+import java.time.temporal.TemporalAccessor;
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Event-time based partition TTL strategy: lifetime is read from the 
partition path, not from
+ * commit metadata. Late-arriving writes into an old partition do not extend 
its lifetime, and
+ * backfilled historic partitions are still considered old. Compare with 
{@link KeepByTimeStrategy}
+ * (last commit time) and {@link KeepByCreationTimeStrategy} (creation commit 
time).
+ *
+ * <h3>Supported path shapes</h3>
+ * The first-class, tested shapes are day and hour granularity. Each example 
shows the partition
+ * path on the left and the required {@code timeSegStartIndex} on the right 
(see
+ * <i>Locating the time block</i> below); non-time segments may appear before 
and/or after the
+ * time block.
+ * <ul>
+ *   <li>Day, {@code format=yyyy-MM-dd}
+ *     <ul>
+ *       <li>time only: {@code 2026-06-27}, {@code dt=2026-06-27} — 
timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time: {@code region=us/2026-06-27}, {@code 
region=us/dt=2026-06-27} — timeSegStartIndex {@code 1}</li>
+ *       <li>time + suffix: {@code 2026-06-27/source=app}, {@code 
dt=2026-06-27/source=app} — timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time + suffix: {@code 
region=us/dt=2026-06-27/source=app} — timeSegStartIndex {@code 1}</li>
+ *     </ul>
+ *   </li>
+ *   <li>Day, {@code format=yyyyMMdd}
+ *     <ul>
+ *       <li>time only: {@code 20260627}, {@code dt=20260627} — 
timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time: {@code region=us/20260627}, {@code 
region=us/dt=20260627} — timeSegStartIndex {@code 1}</li>
+ *       <li>time + suffix: {@code 20260627/source=app}, {@code 
dt=20260627/source=app} — timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time + suffix: {@code region=us/dt=20260627/source=app} 
— timeSegStartIndex {@code 1}</li>
+ *     </ul>
+ *   </li>
+ *   <li>Hour, {@code format=yyyy-MM-dd/HH}
+ *     <ul>
+ *       <li>time only: {@code 2026-06-27/12}, {@code dt=2026-06-27/hh=12} — 
timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time: {@code region=us/2026-06-27/12}, {@code 
region=us/dt=2026-06-27/hh=12} — timeSegStartIndex {@code 1}</li>
+ *       <li>time + suffix: {@code 2026-06-27/12/source=app}, {@code 
dt=2026-06-27/hh=12/source=app} — timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time + suffix: {@code 
region=us/dt=2026-06-27/hh=12/source=app} — timeSegStartIndex {@code 1}</li>
+ *     </ul>
+ *   </li>
+ *   <li>Hour, {@code format=yyyyMMdd/HH}
+ *     <ul>
+ *       <li>time only: {@code 20260627/12}, {@code dt=20260627/hh=12} — 
timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time: {@code region=us/20260627/12}, {@code 
region=us/dt=20260627/hh=12} — timeSegStartIndex {@code 1}</li>
+ *       <li>time + suffix: {@code 20260627/12/source=app}, {@code 
dt=20260627/hh=12/source=app} — timeSegStartIndex {@code 0}</li>
+ *       <li>prefix + time + suffix: {@code 
region=us/dt=20260627/hh=12/source=app} — timeSegStartIndex {@code 1}</li>
+ *     </ul>
+ *   </li>
+ * </ul>
+ * Hive-style key names are not constrained: {@code dt=}, {@code day=}, {@code 
event_date=},
+ * {@code hh=}, {@code hour=} all work; only the value after {@code =} is 
parsed.
+ * <p>
+ * Any {@link java.time.format.DateTimeFormatter} pattern works as long as the 
resulting
+ * {@link java.time.temporal.TemporalAccessor} can be resolved to either an 
{@link java.time.Instant}
+ * or a {@link java.time.LocalDate} (day-only patterns are anchored at UTC 
start-of-day). A
+ * {@code /} in the pattern means the time value spans that many consecutive 
path segments.
+ * Patterns missing day-of-month, e.g. month-only {@code yyyy-MM}, cannot be 
resolved and will
+ * raise the standard parse-failure error at runtime.
+ *
+ * <h3>Locating the time block</h3>
+ * The time block must occupy a <i>contiguous</i> segment range of the 
partition path. Only the
+ * segments before it count toward {@code timeSegStartIndex}; segments after 
are ignored. Interleaved
+ * layouts such as {@code dt=20260627/source=app/hh=12} are not supported -- 
the time block must
+ * be in one piece.
+ *
+ * <h3>Time zone</h3>
+ * Both the partition's event time and the cutoff derived from {@code 
instantTime} are interpreted
+ * in UTC. Set {@code hoodie.table.timeline.timezone=UTC} so the timeline 
writes instants under the
+ * same convention; otherwise the cutoff drifts by the JVM's UTC offset -- a 
boundary effect at
+ * day granularity, a full-offset shift at hour granularity.
+ *
+ * <h3>Configuration</h3>
+ * All three knobs come with defaults, so a table whose partition path is 
purely a date in
+ * {@code yyyy-MM-dd} form works out of the box.
+ * <ul>
+ *   <li>{@link org.apache.hudi.config.HoodieTTLConfig#EVENT_TIME_FORMAT} — 
date-time pattern of
+ *       the time block in the partition path. Default {@code yyyy-MM-dd}. A 
{@code /} in the
+ *       pattern means the time block spans that many consecutive 
segments.</li>
+ *   <li>{@link 
org.apache.hudi.config.HoodieTTLConfig#EVENT_TIME_SEGMENT_START_INDEX} —
+ *       0-based index of the first segment that carries the time block. 
Default {@code 0}.
+ *       Raise it when non-time segments come before the time block (see 
examples above).</li>
+ *   <li>{@link 
org.apache.hudi.config.HoodieTTLConfig#EVENT_TIME_DELETE_HIVE_DEFAULT_PARTITION}
 —
+ *       whether to treat partitions whose time block contains {@code 
__HIVE_DEFAULT_PARTITION__}
+ *       in <i>any</i> segment as expired. Such a partition has an undefined 
event time (one of
+ *       its event-time columns was {@code NULL}, so the row cannot be placed 
on the configured
+ *       time axis) and falls outside the normal cutoff comparison. Default 
{@code false}, i.e.
+ *       such partitions are skipped with a WARN and the user keeps explicit 
control over them.
+ *       Applies to both single-segment formats (e.g. {@code 
dt=__HIVE_DEFAULT_PARTITION__}) and
+ *       multi-segment ones (e.g. {@code 
dt=2026-06-28/hh=__HIVE_DEFAULT_PARTITION__}).</li>
+ * </ul>
+ */
+@Slf4j
+public class KeepByEventTimeStrategy extends KeepByTimeStrategy {
+
+  private final String eventTimeFormat;
+  private final int timeSegStartIndex;
+  private final boolean shouldDeleteHiveDefaultPartition;
+  private final boolean hiveStylePartitioning;
+
+  public KeepByEventTimeStrategy(HoodieTable hoodieTable, String instantTime) {
+    super(hoodieTable, instantTime);
+    // Defaults: format='yyyy-MM-dd', timeSegStartIndex=0, 
deleteHiveDefaultPartition=false. The
+    // two guards below catch users who set the values explicitly to 
obviously-broken inputs.
+    this.eventTimeFormat = writeConfig.getPartitionTTLEventTimeFormat();
+    if (eventTimeFormat == null || eventTimeFormat.isEmpty()) {
+      throw new IllegalArgumentException(
+          HoodieTTLConfig.EVENT_TIME_FORMAT.key() + " must not be empty.");
+    }
+    this.timeSegStartIndex = 
writeConfig.getPartitionTTLEventTimeSegmentStartIndex();
+    if (timeSegStartIndex < 0) {
+      throw new IllegalArgumentException(
+          HoodieTTLConfig.EVENT_TIME_SEGMENT_START_INDEX.key() + " must be >= 
0, got " + timeSegStartIndex);
+    }
+    this.shouldDeleteHiveDefaultPartition = 
writeConfig.shouldPartitionTTLEventTimeDeleteHiveDefaultPartition();
+    // Hive-style partitioning is a table-level property recorded at table 
creation; trust it
+    // rather than guessing per-segment from a stray '=' character in a value.
+    this.hiveStylePartitioning = Boolean.parseBoolean(
+        
hoodieTable.getMetaClient().getTableConfig().getHiveStylePartitioningEnable());
+  }
+
+  @Override
+  protected List<String> getExpiredPartitionsForTimeStrategy(List<String> 
partitionPathsForTTL) {
+    long cutoffMillis = resolveCutoffMillis(instantTime, ttlInMilis);
+    DateTimeFormatter formatter = 
DateTimeFormatter.ofPattern(eventTimeFormat).withZone(ZoneOffset.UTC);
+    int segCount = segmentCount(eventTimeFormat);
+
+    // Step 1: filter by event time. Pure computation over immutable inputs 
(no shared state, no
+    // I/O), so a raw parallel stream on the common ForkJoinPool is safe. In a 
healthy table the
+    // vast majority of partitions survive this filter, so most of the work 
stays here and never
+    // reaches the more expensive step 2.
+    List<String> eventTimeExpired = partitionPathsForTTL.stream().parallel()
+        .filter(path -> isPartitionExpiredByEventTime(
+            path, formatter, timeSegStartIndex, segCount, cutoffMillis,
+            shouldDeleteHiveDefaultPartition, hiveStylePartitioning))
+        .collect(Collectors.toList());
+    if (eventTimeExpired.isEmpty()) {
+      return Collections.emptyList();
+    }
+
+    // Step 2: drop partitions that an earlier TTL replace already emptied. 
Their event time is
+    // derived from the (unchanged) path, so without this filter they would be 
re-selected on
+    // every batch -- issuing an empty replace commit each time and never 
converging. Keep only
+    // partitions that still have a live file slice, mirroring 
KeepByTimeStrategy which keys off
+    // the surviving slices' last commit time and thus naturally skips deleted 
ones.
+    //
+    // hasLiveFileSlice touches hoodieTable.getHoodieView(), which for 
non-default view types
+    // (SPILLABLE_DISK, EMBEDDED_KV_STORE) mutates a backing store during 
first-time partition
+    // load under a shared read lock -- unsafe under unbounded concurrent 
access on the common
+    // ForkJoinPool. Route the lookup through the engine context with bounded 
parallelism, the
+    // same pattern KeepByTimeStrategy#getLastCommitTimeForPartitions uses, so 
that blocking file
+    // listings don't run on the common pool and respect 
getPartitionTTLStatsMaxParallelism.
+    int statsParallelism = Math.min(eventTimeExpired.size(), 
writeConfig.getPartitionTTLStatsMaxParallelism());
+    return hoodieTable.getContext().map(eventTimeExpired,
+        partitionPath -> Pair.of(partitionPath, 
hasLiveFileSlice(partitionPath)),
+        statsParallelism).stream()
+        .filter(Pair::getRight)
+        .map(Pair::getLeft)
+        .collect(Collectors.toList());
+  }
+
+  /**
+   * Whether the partition still has at least one live file slice as of {@code 
instantTime}.
+   * File groups replaced by an earlier TTL delete are excluded by the file 
system view, so an
+   * already-deleted partition returns {@code false} here even while its 
directory lingers on
+   * storage awaiting the cleaner.
+   */
+  private boolean hasLiveFileSlice(String partitionPath) {
+    return hoodieTable.getHoodieView()
+        .getLatestFileSlicesBeforeOrOn(partitionPath, instantTime, true)
+        .findAny()
+        .isPresent();
+  }
+
+  /**
+   * Number of '/'-separated path segments the configured format occupies.
+   * Example: {@code yyyy-MM-dd/HH} -> 2.
+   */
+  static int segmentCount(String format) {
+    return format.split("/").length;
+  }
+
+  /**

Review Comment:
   🤖 nit: the method's own Javadoc calls out that the two trailing `boolean` 
params are easy to transpose — could you consider bundling 
`deleteHiveDefaultPartition` and `hiveStylePartitioning` (and maybe the other 
config fields) into a small `EventTimeParseContext` value object? Even just 
reordering so `hiveStylePartitioning` (a table-level constant) comes before 
`deleteHiveDefaultPartition` (user opt-in, opposite semantics) would reduce the 
risk at call sites.
   
   <sub><i>⚠️ AI-generated; verify before applying. React 👍/👎 to flag 
quality.</i></sub>



##########
hudi-client/hudi-client-common/src/main/java/org/apache/hudi/table/action/ttl/strategy/KeepByEventTimeStrategy.java:
##########
@@ -0,0 +1,275 @@
+/*
+ * 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.hudi.table.action.ttl.strategy;
+
+import org.apache.hudi.common.table.timeline.HoodieInstantTimeGenerator;
+import org.apache.hudi.common.util.PartitionPathEncodeUtils;
+import org.apache.hudi.table.HoodieTable;
+
+import lombok.extern.slf4j.Slf4j;
+
+import java.text.ParseException;
+import java.time.ZoneOffset;
+import java.time.format.DateTimeFormatter;
+import java.time.format.DateTimeParseException;
+import java.time.temporal.TemporalAccessor;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Event-time based partition TTL strategy: lifetime is read from the 
partition path, not from
+ * commit metadata. Late-arriving writes into an old partition do not extend 
its lifetime, and
+ * backfilled historic partitions are still considered old. Compare with 
{@link KeepByTimeStrategy}
+ * (last commit time) and {@link KeepByCreationTimeStrategy} (creation commit 
time).
+ *
+ * <h3>Supported path shapes</h3>
+ * The first-class, tested shapes are day and hour granularity. Each example 
shows the partition
+ * path on the left and the required {@code startIndex} on the right (see
+ * <i>Locating the time block</i> below); non-time segments may appear before 
and/or after the
+ * time block.
+ * <ul>
+ *   <li>Day, {@code format=yyyy-MM-dd}
+ *     <ul>
+ *       <li>time only: {@code 2026-06-27}, {@code dt=2026-06-27} — startIndex 
{@code 0}</li>
+ *       <li>prefix + time: {@code region=us/2026-06-27}, {@code 
region=us/dt=2026-06-27} — startIndex {@code 1}</li>
+ *       <li>time + suffix: {@code 2026-06-27/source=app}, {@code 
dt=2026-06-27/source=app} — startIndex {@code 0}</li>
+ *       <li>prefix + time + suffix: {@code 
region=us/dt=2026-06-27/source=app} — startIndex {@code 1}</li>
+ *     </ul>
+ *   </li>
+ *   <li>Day, {@code format=yyyyMMdd}
+ *     <ul>
+ *       <li>time only: {@code 20260627}, {@code dt=20260627} — startIndex 
{@code 0}</li>
+ *       <li>prefix + time: {@code region=us/20260627}, {@code 
region=us/dt=20260627} — startIndex {@code 1}</li>
+ *       <li>time + suffix: {@code 20260627/source=app}, {@code 
dt=20260627/source=app} — startIndex {@code 0}</li>
+ *       <li>prefix + time + suffix: {@code region=us/dt=20260627/source=app} 
— startIndex {@code 1}</li>
+ *     </ul>
+ *   </li>
+ *   <li>Hour, {@code format=yyyy-MM-dd/HH}
+ *     <ul>
+ *       <li>time only: {@code 2026-06-27/12}, {@code dt=2026-06-27/hh=12} — 
startIndex {@code 0}</li>
+ *       <li>prefix + time: {@code region=us/2026-06-27/12}, {@code 
region=us/dt=2026-06-27/hh=12} — startIndex {@code 1}</li>
+ *       <li>time + suffix: {@code 2026-06-27/12/source=app}, {@code 
dt=2026-06-27/hh=12/source=app} — startIndex {@code 0}</li>
+ *       <li>prefix + time + suffix: {@code 
region=us/dt=2026-06-27/hh=12/source=app} — startIndex {@code 1}</li>
+ *     </ul>
+ *   </li>
+ *   <li>Hour, {@code format=yyyyMMdd/HH}
+ *     <ul>
+ *       <li>time only: {@code 20260627/12}, {@code dt=20260627/hh=12} — 
startIndex {@code 0}</li>
+ *       <li>prefix + time: {@code region=us/20260627/12}, {@code 
region=us/dt=20260627/hh=12} — startIndex {@code 1}</li>
+ *       <li>time + suffix: {@code 20260627/12/source=app}, {@code 
dt=20260627/hh=12/source=app} — startIndex {@code 0}</li>
+ *       <li>prefix + time + suffix: {@code 
region=us/dt=20260627/hh=12/source=app} — startIndex {@code 1}</li>
+ *     </ul>
+ *   </li>
+ * </ul>
+ * Hive-style key names are not constrained: {@code dt=}, {@code day=}, {@code 
event_date=},
+ * {@code hh=}, {@code hour=} all work; only the value after {@code =} is 
parsed.
+ * <p>
+ * Any {@link java.time.format.DateTimeFormatter} pattern works as long as the 
resulting
+ * {@link java.time.temporal.TemporalAccessor} can be resolved to either an 
{@link java.time.Instant}
+ * or a {@link java.time.LocalDate} (day-only patterns are anchored at UTC 
start-of-day). A
+ * {@code /} in the pattern means the time value spans that many consecutive 
path segments.
+ * Patterns missing day-of-month, e.g. month-only {@code yyyy-MM}, cannot be 
resolved and will
+ * raise the standard parse-failure error at runtime.
+ *
+ * <h3>Locating the time block</h3>
+ * The time block must occupy a <i>contiguous</i> segment range of the 
partition path. Only the
+ * segments before it count toward {@code startIndex}; segments after are 
ignored. Interleaved
+ * layouts such as {@code dt=20260627/source=app/hh=12} are not supported -- 
the time block must
+ * be in one piece.
+ *
+ * <h3>Time zone</h3>
+ * Both the partition's event time and the cutoff derived from {@code 
instantTime} are interpreted
+ * in UTC. Set {@code hoodie.table.timeline.timezone=UTC} so the timeline 
writes instants under the
+ * same convention; otherwise the cutoff drifts by the JVM's UTC offset -- a 
boundary effect at
+ * day granularity, a full-offset shift at hour granularity.
+ *
+ * <h3>Configuration</h3>
+ * All three knobs come with defaults, so a table whose partition path is 
purely a date in
+ * {@code yyyy-MM-dd} form works out of the box.
+ * <ul>
+ *   <li>{@link org.apache.hudi.config.HoodieTTLConfig#EVENT_TIME_FORMAT} — 
date-time pattern of
+ *       the time block in the partition path. Default {@code yyyy-MM-dd}. A 
{@code /} in the
+ *       pattern means the time block spans that many consecutive 
segments.</li>
+ *   <li>{@link 
org.apache.hudi.config.HoodieTTLConfig#EVENT_TIME_PARTITION_START_INDEX} —
+ *       0-based index of the first segment that carries the time block. 
Default {@code 0}.
+ *       Raise it when non-time segments come before the time block (see 
examples above).</li>
+ *   <li>{@link 
org.apache.hudi.config.HoodieTTLConfig#EVENT_TIME_DELETE_HIVE_DEFAULT_PARTITION}
 —
+ *       whether to treat partitions containing {@code 
__HIVE_DEFAULT_PARTITION__} (i.e. data
+ *       whose event-time column was {@code NULL}) as expired. Default {@code 
false}, i.e. such
+ *       partitions are skipped with a WARN and the user keeps explicit 
control over them.</li>
+ * </ul>
+ */
+@Slf4j
+public class KeepByEventTimeStrategy extends KeepByTimeStrategy {
+
+  private final String eventTimeFormat;
+  private final int startIndex;
+  private final boolean deleteHiveDefaultPartition;
+  private final boolean hiveStylePartitioning;
+
+  public KeepByEventTimeStrategy(HoodieTable hoodieTable, String instantTime) {
+    super(hoodieTable, instantTime);
+    // Defaults: format='yyyy-MM-dd', startIndex=0, 
deleteHiveDefaultPartition=false. The two
+    // guards below catch users who set the values explicitly to 
obviously-broken inputs.
+    this.eventTimeFormat = writeConfig.getPartitionTTLEventTimeFormat();
+    if (eventTimeFormat == null || eventTimeFormat.isEmpty()) {
+      throw new IllegalArgumentException(
+          "hoodie.partition.ttl.strategy.event.time.format must not be 
empty.");
+    }
+    this.startIndex = 
writeConfig.getPartitionTTLEventTimePartitionStartIndex();
+    if (startIndex < 0) {
+      throw new IllegalArgumentException(
+          "hoodie.partition.ttl.strategy.event.time.partition.start.index must 
be >= 0, got " + startIndex);
+    }
+    this.deleteHiveDefaultPartition = 
writeConfig.shouldDeleteHiveDefaultPartitionForEventTimeTTL();
+    // Hive-style partitioning is a table-level property recorded at table 
creation; trust it
+    // rather than guessing per-segment from a stray '=' character in a value.
+    this.hiveStylePartitioning = Boolean.parseBoolean(
+        
hoodieTable.getMetaClient().getTableConfig().getHiveStylePartitioningEnable());
+  }
+
+  @Override
+  protected List<String> getExpiredPartitionsForTimeStrategy(List<String> 
partitionPathsForTTL) {
+    long cutoffMillis = resolveCutoffMillis(instantTime, ttlInMilis);

Review Comment:
   🤖 I don't think this overflow holds against the current code. `ttlInMilis` 
in the parent `KeepByTimeStrategy` is 
`TimeUnit.DAYS.toMillis(writeConfig.getPartitionTTLStrategyDaysRetain())`, not 
`days * 1000 * 3600 * 24`. `toMillis(long)` widens its argument to `long` 
before multiplying, so the whole computation is 64-bit and 30/90/365-day 
retentions don't wrap. Worth double-checking, but I believe the premise here is 
stale. A realistic-retention test (e.g. 90 days) is still a nice addition 
regardless.



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