From c3cacd148c7d0b235c0ee17e826c29e272be2b0b Mon Sep 17 00:00:00 2001
From: Martin Gaievski <gaievski@amazon.com>
Date: Thu, 19 Dec 2024 13:57:44 -0800
Subject: [PATCH] Use max_window_size as max for pagination depth

Signed-off-by: Martin Gaievski <gaievski@amazon.com>
---
 .../neuralsearch/query/HybridQueryBuilder.java     | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/main/java/org/opensearch/neuralsearch/query/HybridQueryBuilder.java b/src/main/java/org/opensearch/neuralsearch/query/HybridQueryBuilder.java
index 0b52b90e6..c6123c8bf 100644
--- a/src/main/java/org/opensearch/neuralsearch/query/HybridQueryBuilder.java
+++ b/src/main/java/org/opensearch/neuralsearch/query/HybridQueryBuilder.java
@@ -59,7 +59,6 @@ public final class HybridQueryBuilder extends AbstractQueryBuilder<HybridQueryBu
     static final int MAX_NUMBER_OF_SUB_QUERIES = 5;
     private final static int DEFAULT_PAGINATION_DEPTH = 10;
     private static final int LOWER_BOUND_OF_PAGINATION_DEPTH = 1;
-    private static final int UPPER_BOUND_OF_PAGINATION_DEPTH = 10000;
 
     public HybridQueryBuilder(StreamInput in) throws IOException {
         super(in);
@@ -128,6 +127,7 @@ protected Query doToQuery(QueryShardContext queryShardContext) throws IOExceptio
         if (queryCollection.isEmpty()) {
             return Queries.newMatchNoDocsQuery(String.format(Locale.ROOT, "no clauses for %s query", NAME));
         }
+        validatePaginationDepth(paginationDepth, queryShardContext);
         return new HybridQuery(queryCollection, paginationDepth);
     }
 
@@ -236,7 +236,6 @@ public static HybridQueryBuilder fromXContent(XContentParser parser) throws IOEx
         compoundQueryBuilder.queryName(queryName);
         compoundQueryBuilder.boost(boost);
         if (isClusterOnOrAfterMinReqVersionForPaginationInHybridQuery()) {
-            validatePaginationDepth(paginationDepth);
             compoundQueryBuilder.paginationDepth(paginationDepth);
         }
         for (QueryBuilder query : queries) {
@@ -326,9 +325,14 @@ private Collection<Query> toQueries(Collection<QueryBuilder> queryBuilders, Quer
         return queries;
     }
 
-    private static void validatePaginationDepth(Integer paginationDepth) {
-        if (paginationDepth != null
-            && (paginationDepth < LOWER_BOUND_OF_PAGINATION_DEPTH || paginationDepth > UPPER_BOUND_OF_PAGINATION_DEPTH)) {
+    private static void validatePaginationDepth(Integer paginationDepth, QueryShardContext queryShardContext) {
+        if (Objects.isNull(paginationDepth)) {
+            return;
+        }
+        // compare pagination depth with OpenSearch setting index.max_result_window
+        // see https://opensearch.org/docs/latest/install-and-configure/configuring-opensearch/index-settings/
+        int maxResultWindowIndexSetting = queryShardContext.getIndexSettings().getMaxResultWindow();
+        if (paginationDepth < LOWER_BOUND_OF_PAGINATION_DEPTH || paginationDepth > maxResultWindowIndexSetting) {
             throw new IllegalArgumentException(
                 String.format(Locale.ROOT, "Pagination depth should lie in the range of 1-1000. Received: %s", paginationDepth)
             );