Added the code to disable the graph builds and create graphs once

Signed-off-by: Navneet Verma <navneev@amazon.com>

.gitattributes

@@ -0,0 +1 @@
+*.tar.gz filter=lfs diff=lfs merge=lfs -text

DEVELOPER_GUIDE.md

@@ -430,3 +430,35 @@ original PR with an appropriate label `backport <backport-branch-name>` is merge
 run successfully on the PR. For example, if a PR on main needs to be backported to `1.x` branch, add a label 
 `backport 1.x` to the PR and make sure the backport workflow runs on the PR along with other checks. Once this PR is 
 merged to main, the workflow will create a backport PR to the `1.x` branch.
+
+
+## Creating graphs once
+1. Run this command to setup the cluster (code for OS: https://github.com/navneet1v/OpenSearch/tree/build-time)
+```
+./gradlew run -PcustomDistributionUrl="/path/to/repo/k-NN/temp/cluster.tar.gz"
+```
+2. First disable graph creation:
+```
+PUT _cluster/settings
+{
+	"persistent": {
+		"knn.create_graphs": false
+	}
+}
+```
+
+3. Now go ahead and index your data. and force merge segments down to 1.
+4. Now enable the graph creation.
+```
+PUT _cluster/settings
+{
+	"persistent": {
+		"knn.create_graphs": true
+	}
+}
+```
+5. Now hit this API:
+```
+POST <index-name>/_forcemerge?one_merge=true
+```
+The above API will create a new segment and graph will be generated for that segment.

src/main/java/org/opensearch/knn/index/KNNSettings.java

@@ -108,6 +108,12 @@ public class KNNSettings {
         Setting.Property.Deprecated
     );
 
+    public static final Setting<Boolean> CREATE_GRAPHS = Setting.boolSetting(
+        "knn.create_graphs",
+        false,
+        NodeScope, Dynamic
+    );
+
     /**
      * M - the number of bi-directional links created for every new element during construction.
      * Reasonable range for M is 2-100. Higher M work better on datasets with high intrinsic
@@ -354,6 +360,10 @@ private Setting<?> getSetting(String key) {
             return KNN_FAISS_AVX2_DISABLED_SETTING;
         }
 
+        if("knn.create_graphs".equals(key)) {
+            return CREATE_GRAPHS;
+        }
+
         throw new IllegalArgumentException("Cannot find setting by key [" + key + "]");
     }
 
@@ -371,7 +381,7 @@ public List<Setting<?>> getSettings() {
             MODEL_INDEX_NUMBER_OF_REPLICAS_SETTING,
             MODEL_CACHE_SIZE_LIMIT_SETTING,
             ADVANCED_FILTERED_EXACT_SEARCH_THRESHOLD_SETTING,
-            KNN_FAISS_AVX2_DISABLED_SETTING
+            KNN_FAISS_AVX2_DISABLED_SETTING, CREATE_GRAPHS
         );
         return Stream.concat(settings.stream(), dynamicCacheSettings.values().stream()).collect(Collectors.toList());
     }
@@ -513,6 +523,10 @@ public void onIndexModule(IndexModule module) {
         });
     }
 
+    public static boolean canCreateGraphs() {
+        return KNNSettings.state().getSettingValue("knn.create_graphs");
+    }
+
     private static String percentageAsString(Integer percentage) {
         return percentage + "%";
     }

src/main/java/org/opensearch/knn/index/codec/KNN80Codec/KNN80DocValuesConsumer.java

@@ -108,6 +108,11 @@ private KNNEngine getKNNEngine(@NonNull FieldInfo field) {
 
     public void addKNNBinaryField(FieldInfo field, DocValuesProducer valuesProducer, boolean isMerge, boolean isRefresh)
         throws IOException {
+        if(KNNSettings.canCreateGraphs() == false) {
+            log.info("Not creating graphs as value is : {}", KNNSettings.canCreateGraphs());
+            return;
+        }
+        log.info("Creating graphs as value is : {}", KNNSettings.canCreateGraphs());
         // Get values to be indexed
         BinaryDocValues values = valuesProducer.getBinary(field);
         KNNCodecUtil.Pair pair = KNNCodecUtil.getFloats(values);