docs: add Index Management Enhancements report for v3.3.0

docs/features/index-management/index-management.md

@@ -232,6 +232,9 @@ PUT _plugins/_rollup/jobs/sample_rollup
 
 | Version | PR | Description |
 |---------|-----|-------------|
+| v3.3.0 | [#1460](https://github.com/opensearch-project/index-management/pull/1460) | Using Scripted Avg Class in AvgAggregationBuilder for rollup aggregation fix |
+| v3.3.0 | [#1491](https://github.com/opensearch-project/index-management/pull/1491) | Fix the build for upstream OpenSearch changes |
+| v3.3.0 | [#1473](https://github.com/opensearch-project/index-management/pull/1473) | Dependabot: bump 1password/load-secrets-action from 2 to 3 |
 | v3.2.0 | [#1440](https://github.com/opensearch-project/index-management/pull/1440) | Support for no_alias and min_state_age in ISM Transitions |
 | v3.2.0 | [#1444](https://github.com/opensearch-project/index-management/pull/1444) | Add history index pattern to System Index descriptors |
 | v3.2.0 | [#1442](https://github.com/opensearch-project/index-management/pull/1442) | Fix Integration test and lint errors |
@@ -265,6 +268,7 @@ PUT _plugins/_rollup/jobs/sample_rollup
 
 ## Change History
 
+- **v3.3.0** (2026-01-11): Fixed rollup aggregation reduction bug when searching rollup and raw indices together by using ScriptedAvg class, build fixes for upstream OpenSearch changes, dependency updates
 - **v3.2.0** (2026-01-10): Added `no_alias` and `min_state_age` transition conditions for ISM, registered ISM history index as System Index descriptor, fixed integration tests and lint errors
 - **v3.1.0** (2026-01-10): Fixed false positive notifications in Snapshot Management by suppressing user notifications for internal VersionConflictEngineException errors
 - **v3.0.0** (2025-05-06): Added ISM unfollow action for CCR, rollup target index settings, CVE fixes, Java Agent migration

docs/releases/v3.3.0/features/index-management/index-management-enhancements.md

@@ -0,0 +1,93 @@
+# Index Management Enhancements
+
+## Summary
+
+This release includes bug fixes and maintenance updates for the Index Management plugin, including a fix for rollup aggregation reduction when searching across rollup and raw indices together, build fixes for upstream OpenSearch changes, and a dependency update for the 1password/load-secrets-action GitHub Action.
+
+## Details
+
+### What's New in v3.3.0
+
+#### Rollup Aggregation Fix (ScriptedAvg Class)
+
+The main enhancement addresses a bug in the rollup feature when searching rollup and raw indices together (introduced in v2.18.0). The fix uses the `ScriptedAvg` class in `AvgAggregationBuilder` instead of raw double arrays, enabling proper handling during aggregation reduction.
+
+**Problem**: When searching across both rollup and non-rollup indices, a `ClassCastException` occurred during the reduce phase of `InternalValueCount` and `InternalAvg` aggregations because both used `InternalScriptedMetric` internally.
+
+**Solution**: Updated the scripted metric aggregation scripts in `RollupUtils.kt` to use `ScriptedAvg` class for proper type handling:
+
+```kotlin
+// Before (v3.2.0 and earlier)
+combineScript: "def d = new double[2]; d[0] = state.sums; d[1] = state.counts; return d"
+reduceScript: "... for (a in states) { sum += a[0]; count += a[1]; } ..."
+
+// After (v3.3.0)
+combineScript: "def d = new org.opensearch.search.aggregations.metrics.ScriptedAvg(state.sums, state.counts); return d"
+reduceScript: "... for (a in states) { sum += a.getSum(); count += a.getCount(); } ..."
+```
+
+This change depends on OpenSearch core PR [#18411](https://github.com/opensearch-project/OpenSearch/pull/18411) which added support for `InternalScriptedMetric` in `InternalValueCount` and `InternalAvg` reduction.
+
+#### Build Fixes
+
+Updated test infrastructure to accommodate upstream OpenSearch changes:
+- Changed `LockService` instantiation in unit tests from direct constructor to mock
+- Updated `randomUser()` helper to generate proper custom attribute names format (`key=value`)
+- Added `error_prone_annotations` dependency resolution
+- Removed deprecated `log4j-core` test dependency
+
+#### Dependency Update
+
+Bumped `1password/load-secrets-action` from v2 to v3 in GitHub Actions workflows. This is a breaking change in the action that sets `export-env` to `false` by default.
+
+### Technical Changes
+
+#### Modified Files
+
+| File | Change |
+|------|--------|
+| `RollupUtils.kt` | Updated scripted metric scripts to use `ScriptedAvg` class |
+| `RollupInterceptorIT.kt` | Added `value_count` aggregation to test coverage |
+| `spi/build.gradle` | Added `error_prone_annotations` dependency |
+| `TestHelpers.kt` | Updated `randomUser()` for custom attribute format |
+| Multiple `*StepTests.kt` | Changed `LockService` to mock |
+
+### Usage Example
+
+Searching across rollup and raw indices with avg aggregation now works correctly:
+
+```json
+GET sample-data-*,sample-rollup/_search
+{
+  "size": 0,
+  "aggs": {
+    "avg_value": { "avg": { "field": "value" } },
+    "sum_value": { "sum": { "field": "value" } },
+    "count_value": { "value_count": { "field": "value" } }
+  }
+}
+```
+
+## Limitations
+
+- The rollup aggregation fix requires OpenSearch core v3.3.0+ with the `ScriptedAvg` class support
+- Mixed rollup/raw index search still requires `plugins.rollup.search.search_source_indices: true`
+
+## Related PRs
+
+| PR | Description |
+|----|-------------|
+| [#1460](https://github.com/opensearch-project/index-management/pull/1460) | Using Scripted Avg Class in AvgAggregationBuilder in place of double |
+| [#1491](https://github.com/opensearch-project/index-management/pull/1491) | Fix the build |
+| [#1473](https://github.com/opensearch-project/index-management/pull/1473) | Dependabot: bump 1password/load-secrets-action from 2 to 3 |
+
+## References
+
+- [OpenSearch PR #18411](https://github.com/opensearch-project/OpenSearch/pull/18411): Core changes for InternalScriptedMetric support in aggregation reduction
+- [OpenSearch PR #18288](https://github.com/opensearch-project/OpenSearch/pull/18288): Related aggregation changes
+- [Index Rollups Documentation](https://docs.opensearch.org/3.3/im-plugin/index-rollups/index/)
+- [Index Rollups API](https://docs.opensearch.org/3.3/im-plugin/index-rollups/rollup-api/)
+
+## Related Feature Report
+
+- [Full feature documentation](../../../../features/index-management/index-management.md)

docs/releases/v3.3.0/index.md

@@ -125,6 +125,10 @@
 
 - [Geospatial Deprecation Fixes](features/geospatial/geospatial-deprecation-fixes.md)
 
+### Index Management
+
+- [Index Management Enhancements](features/index-management/index-management-enhancements.md)
+
 ### Query Insights
 
 - [Query Insights Bug Fixes](features/query-insights/query-insights-bug-fixes.md)