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The following commit(s) were added to refs/heads/branch_10_0 by this push:
new ae8b468b104 SOLR-17725: Add MergePolicy to block older segments from
participating in merges (#3883)
ae8b468b104 is described below
commit ae8b468b1043c6e50a387756d9ceab8d1fe974c7
Author: Rahul Goswami <[email protected]>
AuthorDate: Tue Dec 2 20:53:29 2025 -0500
SOLR-17725: Add MergePolicy to block older segments from participating in
merges (#3883)
Helps with Solr upgrades in conjunction with re-indexing.
New: LatestVersionFilterMergePolicy
---------
Co-authored-by: Rahul Goswami <[email protected]>
---
...-for-compatibility-with-future-Solr-version.yml | 8 ++
.../solr/index/LatestVersionFilterMergePolicy.java | 111 +++++++++++++++++++++
.../index/LatestVersionMergePolicyFactory.java | 43 ++++++++
3 files changed, 162 insertions(+)
diff --git
a/changelog/unreleased/SOLR-17725-Merge-policy-to-upgrade-index-for-compatibility-with-future-Solr-version.yml
b/changelog/unreleased/SOLR-17725-Merge-policy-to-upgrade-index-for-compatibility-with-future-Solr-version.yml
new file mode 100644
index 00000000000..502be026e8e
--- /dev/null
+++
b/changelog/unreleased/SOLR-17725-Merge-policy-to-upgrade-index-for-compatibility-with-future-Solr-version.yml
@@ -0,0 +1,8 @@
+# See https://github.com/apache/solr/blob/main/dev-docs/changelog.adoc
+title: Merge policy to upgrade index for compatibility with future Solr version
+type: added
+authors:
+ - name: Rahul Goswami
+links:
+ - name: SOLR-17725
+ url: https://issues.apache.org/jira/browse/SOLR-17725
diff --git
a/solr/core/src/java/org/apache/solr/index/LatestVersionFilterMergePolicy.java
b/solr/core/src/java/org/apache/solr/index/LatestVersionFilterMergePolicy.java
new file mode 100644
index 00000000000..c5a088220b2
--- /dev/null
+++
b/solr/core/src/java/org/apache/solr/index/LatestVersionFilterMergePolicy.java
@@ -0,0 +1,111 @@
+/*
+ * 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.solr.index;
+
+import java.io.IOException;
+import java.util.Map;
+import org.apache.lucene.index.FilterMergePolicy;
+import org.apache.lucene.index.MergePolicy;
+import org.apache.lucene.index.MergeTrigger;
+import org.apache.lucene.index.SegmentCommitInfo;
+import org.apache.lucene.index.SegmentInfos;
+import org.apache.lucene.util.Version;
+
+/**
+ * Prevents any older version segment (i.e. older than current lucene major
version), either
+ * original or one derived as a result of merging with an older version
segment, from being
+ * considered for merges. That way a snapshot of older segments remains
consistent. This assists in
+ * upgrading to a future Lucene major version if existing documents are
reindexed in the current
+ * version with this merge policy in place.
+ */
+public class LatestVersionFilterMergePolicy extends FilterMergePolicy {
+
+ public LatestVersionFilterMergePolicy(MergePolicy in) {
+ super(in);
+ }
+
+ @Override
+ public MergeSpecification findMerges(
+ MergeTrigger mergeTrigger, SegmentInfos infos, MergeContext
mergeContext) throws IOException {
+ return in.findMerges(mergeTrigger, getFilteredInfos(infos), mergeContext);
+ }
+
+ @Override
+ public MergeSpecification findForcedMerges(
+ SegmentInfos infos,
+ int maxSegmentCount,
+ Map<SegmentCommitInfo, Boolean> segmentsToMerge,
+ MergeContext mergeContext)
+ throws IOException {
+ return in.findForcedMerges(
+ getFilteredInfos(infos), maxSegmentCount, segmentsToMerge,
mergeContext);
+ }
+
+ @Override
+ public MergeSpecification findForcedDeletesMerges(SegmentInfos infos,
MergeContext mergeContext)
+ throws IOException {
+ return in.findForcedDeletesMerges(getFilteredInfos(infos), mergeContext);
+ }
+
+ @Override
+ public MergeSpecification findFullFlushMerges(
+ MergeTrigger mergeTrigger, SegmentInfos infos, MergeContext
mergeContext) throws IOException {
+ return in.findFullFlushMerges(mergeTrigger, getFilteredInfos(infos),
mergeContext);
+ }
+
+ private SegmentInfos getFilteredInfos(SegmentInfos infos) {
+ SegmentInfos infosClone = null;
+
+ for (SegmentCommitInfo info : infos) {
+ if (!allowSegmentForMerge(info)) {
+ // There are older version segments present.
+ // We should not remove from the original SegmentInfos. Hence we clone.
+ infosClone = infos.clone();
+ infosClone.clear();
+ break;
+ }
+ }
+
+ if (infosClone == null) {
+ // All segments are latest major version and allowed to participate in
merge
+ return infos;
+ } else {
+ // Either mixed versions or all older version segments.
+ // If we are here, most runs should fall in the former case.
+ // The latter case should only happen once right after an upgrade, so we
are ok with incurring
+ // this redundant iteration for that one time to keep the logic simple
+ for (SegmentCommitInfo info : infos) {
+ if (allowSegmentForMerge(info)) {
+ infosClone.add(info);
+ }
+ }
+ }
+
+ return infosClone;
+ }
+
+ /**
+ * Determines if a SegmentCommitInfo should be part of the candidate set of
segments that will be
+ * considered for merges. By default, we only allow LATEST version segments
to participate in
+ * merges.
+ */
+ protected boolean allowSegmentForMerge(SegmentCommitInfo info) {
+ return info.info.getMinVersion() != null
+ && info.info.getMinVersion().major == Version.LATEST.major;
+ }
+}
diff --git
a/solr/core/src/java/org/apache/solr/index/LatestVersionMergePolicyFactory.java
b/solr/core/src/java/org/apache/solr/index/LatestVersionMergePolicyFactory.java
new file mode 100644
index 00000000000..047830d3199
--- /dev/null
+++
b/solr/core/src/java/org/apache/solr/index/LatestVersionMergePolicyFactory.java
@@ -0,0 +1,43 @@
+/*
+ * 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.solr.index;
+
+import org.apache.lucene.index.MergePolicy;
+import org.apache.lucene.index.TieredMergePolicy;
+import org.apache.solr.core.SolrResourceLoader;
+import org.apache.solr.schema.IndexSchema;
+
+/**
+ * A {@link MergePolicyFactory} for {@link LatestVersionFilterMergePolicy}
objects. The returned
+ * LatestVersionFilterMergePolicy instance blocks older version segments (<
current version of
+ * Lucene) from participating in merges and delegates the merging to a
TieredMergePolicy instance by
+ * default. This can be used to reindex the data and ensure all segments are
the latest version
+ * segments by the end of the reindexing. This can help prepare the index for
upgrade to a later
+ * version of Solr/Lucene even if it was initially created on a now
unsupported version
+ */
+public class LatestVersionMergePolicyFactory extends SimpleMergePolicyFactory {
+
+ public LatestVersionMergePolicyFactory(
+ SolrResourceLoader resourceLoader, MergePolicyFactoryArgs args,
IndexSchema schema) {
+ super(resourceLoader, args, schema);
+ }
+
+ @Override
+ protected MergePolicy getMergePolicyInstance() {
+ return new LatestVersionFilterMergePolicy(new TieredMergePolicy());
+ }
+}
