From 82786d2061b1b92d4deab775aaacb79b520b8ecc Mon Sep 17 00:00:00 2001
From: Harsh Garg <gkharsh@amazon.com>
Date: Thu, 3 Oct 2024 23:36:46 +0530
Subject: [PATCH] Separating metadata filtering for pagination strategies

Signed-off-by: Harsh Garg <gkharsh@amazon.com>
---
 .../pagination/IndexPaginationStrategy.java   | 31 +++++++-------
 .../pagination/ShardPaginationStrategy.java   | 41 +++++++++++++++++--
 2 files changed, 54 insertions(+), 18 deletions(-)

diff --git a/server/src/main/java/org/opensearch/action/pagination/IndexPaginationStrategy.java b/server/src/main/java/org/opensearch/action/pagination/IndexPaginationStrategy.java
index 869ae736296d8..b4a7b18f8ec18 100644
--- a/server/src/main/java/org/opensearch/action/pagination/IndexPaginationStrategy.java
+++ b/server/src/main/java/org/opensearch/action/pagination/IndexPaginationStrategy.java
@@ -54,8 +54,7 @@ public IndexPaginationStrategy(PageParams pageParams, ClusterState clusterState)
             clusterState,
             pageParams.getSort(),
             Objects.isNull(requestedToken) ? null : requestedToken.lastIndexName,
-            Objects.isNull(requestedToken) ? null : requestedToken.lastIndexCreationTime,
-            false
+            Objects.isNull(requestedToken) ? null : requestedToken.lastIndexCreationTime
         );
 
         // Trim sortedIndicesList to get the list of indices metadata to be sent as response
@@ -69,12 +68,11 @@ public IndexPaginationStrategy(PageParams pageParams, ClusterState clusterState)
         );
     }
 
-    protected static List<IndexMetadata> getEligibleIndices(
+    private static List<IndexMetadata> getEligibleIndices(
         ClusterState clusterState,
         String sortOrder,
         String lastIndexName,
-        Long lastIndexCreationTime,
-        boolean includeLastIndex
+        Long lastIndexCreationTime
     ) {
         if (Objects.isNull(lastIndexName) || Objects.isNull(lastIndexCreationTime)) {
             return PaginationStrategy.getSortedIndexMetadata(
@@ -84,25 +82,28 @@ protected static List<IndexMetadata> getEligibleIndices(
         }
         return PaginationStrategy.getSortedIndexMetadata(
             clusterState,
-            getMetadataFilter(sortOrder, lastIndexName, lastIndexCreationTime, includeLastIndex),
+            getMetadataFilter(sortOrder, lastIndexName, lastIndexCreationTime),
             PageParams.PARAM_ASC_SORT_VALUE.equals(sortOrder) ? ASC_COMPARATOR : DESC_COMPARATOR
         );
     }
 
-    protected static Predicate<IndexMetadata> getMetadataFilter(
-        String sortOrder,
-        String lastIndexName,
-        Long lastIndexCreationTime,
-        boolean includeLastIndex
-    ) {
+    private static Predicate<IndexMetadata> getMetadataFilter(String sortOrder, String lastIndexName, Long lastIndexCreationTime) {
         if (Objects.isNull(lastIndexName) || Objects.isNull(lastIndexCreationTime)) {
             return indexMetadata -> true;
         }
-        boolean isAscendingSort = sortOrder.equals(PageParams.PARAM_ASC_SORT_VALUE);
         return metadata -> {
             if (metadata.getIndex().getName().equals(lastIndexName)) {
-                return includeLastIndex;
-            } else if (metadata.getCreationDate() == lastIndexCreationTime) {
+                return false;
+            } else {
+                return getIndexCreateTimeFilter(sortOrder, lastIndexName, lastIndexCreationTime).test(metadata);
+            }
+        };
+    }
+
+    protected static Predicate<IndexMetadata> getIndexCreateTimeFilter(String sortOrder, String lastIndexName, Long lastIndexCreationTime) {
+        boolean isAscendingSort = sortOrder.equals(PageParams.PARAM_ASC_SORT_VALUE);
+        return metadata -> {
+            if (metadata.getCreationDate() == lastIndexCreationTime) {
                 return isAscendingSort
                     ? metadata.getIndex().getName().compareTo(lastIndexName) > 0
                     : metadata.getIndex().getName().compareTo(lastIndexName) < 0;
diff --git a/server/src/main/java/org/opensearch/action/pagination/ShardPaginationStrategy.java b/server/src/main/java/org/opensearch/action/pagination/ShardPaginationStrategy.java
index 7201578a87aca..768f2993f454b 100644
--- a/server/src/main/java/org/opensearch/action/pagination/ShardPaginationStrategy.java
+++ b/server/src/main/java/org/opensearch/action/pagination/ShardPaginationStrategy.java
@@ -19,6 +19,10 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.function.Predicate;
+
+import static org.opensearch.action.pagination.IndexPaginationStrategy.ASC_COMPARATOR;
+import static org.opensearch.action.pagination.IndexPaginationStrategy.DESC_COMPARATOR;
 
 /**
  * This strategy can be used by the Rest APIs wanting to paginate the responses based on Shards.
@@ -35,12 +39,11 @@ public class ShardPaginationStrategy implements PaginationStrategy<ShardRouting>
     public ShardPaginationStrategy(PageParams pageParams, ClusterState clusterState) {
         ShardStrategyToken shardStrategyToken = getShardStrategyToken(pageParams.getRequestedToken());
         // Get list of indices metadata sorted by their creation time and filtered by the last sent index
-        List<IndexMetadata> filteredIndices = IndexPaginationStrategy.getEligibleIndices(
+        List<IndexMetadata> filteredIndices = getEligibleIndices(
             clusterState,
             pageParams.getSort(),
             Objects.isNull(shardStrategyToken) ? null : shardStrategyToken.lastIndexName,
-            Objects.isNull(shardStrategyToken) ? null : shardStrategyToken.lastIndexCreationTime,
-            true
+            Objects.isNull(shardStrategyToken) ? null : shardStrategyToken.lastIndexCreationTime
         );
         // Get the list of shards and indices belonging to current page.
         this.pageData = getPageData(
@@ -51,6 +54,38 @@ public ShardPaginationStrategy(PageParams pageParams, ClusterState clusterState)
         );
     }
 
+    private static List<IndexMetadata> getEligibleIndices(
+        ClusterState clusterState,
+        String sortOrder,
+        String lastIndexName,
+        Long lastIndexCreationTime
+    ) {
+        if (Objects.isNull(lastIndexName) || Objects.isNull(lastIndexCreationTime)) {
+            return PaginationStrategy.getSortedIndexMetadata(
+                clusterState,
+                PageParams.PARAM_ASC_SORT_VALUE.equals(sortOrder) ? ASC_COMPARATOR : DESC_COMPARATOR
+            );
+        }
+        return PaginationStrategy.getSortedIndexMetadata(
+            clusterState,
+            getMetadataFilter(sortOrder, lastIndexName, lastIndexCreationTime),
+            PageParams.PARAM_ASC_SORT_VALUE.equals(sortOrder) ? ASC_COMPARATOR : DESC_COMPARATOR
+        );
+    }
+
+    private static Predicate<IndexMetadata> getMetadataFilter(String sortOrder, String lastIndexName, Long lastIndexCreationTime) {
+        if (Objects.isNull(lastIndexName) || Objects.isNull(lastIndexCreationTime)) {
+            return indexMetadata -> true;
+        }
+        return metadata -> {
+            if (metadata.getIndex().getName().equals(lastIndexName)) {
+                return true;
+            } else {
+                return IndexPaginationStrategy.getIndexCreateTimeFilter(sortOrder, lastIndexName, lastIndexCreationTime).test(metadata);
+            }
+        };
+    }
+
     /**
      * Will be used to get the list of shards and respective indices to which they belong,
      * which are to be displayed in a page.