From 825748687b8a5e523e9ab7a12592186cfbcef06c Mon Sep 17 00:00:00 2001
From: zhichao-aws <zhichaog@amazon.com>
Date: Mon, 26 Feb 2024 16:10:17 +0800
Subject: [PATCH] feature: implement default model id for neural sparse

Signed-off-by: zhichao-aws <zhichaog@amazon.com>
---
 .../NeuralQueryEnricherProcessor.java         |  5 ++-
 .../query/NeuralSparseQueryBuilder.java       | 34 ++++++++++++++-----
 2 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/src/main/java/org/opensearch/neuralsearch/processor/NeuralQueryEnricherProcessor.java b/src/main/java/org/opensearch/neuralsearch/processor/NeuralQueryEnricherProcessor.java
index b20b889cb..d593503bd 100644
--- a/src/main/java/org/opensearch/neuralsearch/processor/NeuralQueryEnricherProcessor.java
+++ b/src/main/java/org/opensearch/neuralsearch/processor/NeuralQueryEnricherProcessor.java
@@ -67,7 +67,10 @@ private NeuralQueryEnricherProcessor(
     @Override
     public SearchRequest processRequest(SearchRequest searchRequest) {
         QueryBuilder queryBuilder = searchRequest.source().query();
-        queryBuilder.visit(new NeuralSearchQueryVisitor(modelId, neuralFieldDefaultIdMap));
+        /* Use null check to pass the case where users are using empty query body. i.e. GET /index_name/_search */
+        if (queryBuilder != null) {
+            queryBuilder.visit(new NeuralSearchQueryVisitor(modelId, neuralFieldDefaultIdMap));
+        }
         return searchRequest;
     }
 
diff --git a/src/main/java/org/opensearch/neuralsearch/query/NeuralSparseQueryBuilder.java b/src/main/java/org/opensearch/neuralsearch/query/NeuralSparseQueryBuilder.java
index 48c722011..6e87f4c38 100644
--- a/src/main/java/org/opensearch/neuralsearch/query/NeuralSparseQueryBuilder.java
+++ b/src/main/java/org/opensearch/neuralsearch/query/NeuralSparseQueryBuilder.java
@@ -18,6 +18,7 @@
 import org.apache.lucene.search.BooleanClause;
 import org.apache.lucene.search.BooleanQuery;
 import org.apache.lucene.search.Query;
+import org.opensearch.Version;
 import org.opensearch.common.SetOnce;
 import org.opensearch.core.ParseField;
 import org.opensearch.core.action.ActionListener;
@@ -32,6 +33,7 @@
 import org.opensearch.index.query.QueryRewriteContext;
 import org.opensearch.index.query.QueryShardContext;
 import org.opensearch.neuralsearch.ml.MLCommonsClientAccessor;
+import org.opensearch.neuralsearch.util.NeuralSearchClusterUtil;
 import org.opensearch.neuralsearch.util.TokenWeightUtil;
 
 import com.google.common.annotations.VisibleForTesting;
@@ -72,6 +74,7 @@ public static void initialize(MLCommonsClientAccessor mlClient) {
     private String queryText;
     private String modelId;
     private Supplier<Map<String, Float>> queryTokensSupplier;
+    private static final Version MINIMAL_SUPPORTED_VERSION_DEFAULT_MODEL_ID = Version.V_2_13_0;
 
     /**
      * Constructor from stream input
@@ -83,7 +86,11 @@ public NeuralSparseQueryBuilder(StreamInput in) throws IOException {
         super(in);
         this.fieldName = in.readString();
         this.queryText = in.readString();
-        this.modelId = in.readString();
+        if (isClusterOnOrAfterMinReqVersionForDefaultModelIdSupport()) {
+            this.modelId = in.readOptionalString();
+        } else {
+            this.modelId = in.readString();
+        }
         if (in.readBoolean()) {
             Map<String, Float> queryTokens = in.readMap(StreamInput::readString, StreamInput::readFloat);
             this.queryTokensSupplier = () -> queryTokens;
@@ -94,7 +101,11 @@ public NeuralSparseQueryBuilder(StreamInput in) throws IOException {
     protected void doWriteTo(StreamOutput out) throws IOException {
         out.writeString(fieldName);
         out.writeString(queryText);
-        out.writeString(modelId);
+        if (isClusterOnOrAfterMinReqVersionForDefaultModelIdSupport()) {
+            out.writeOptionalString(this.modelId);
+        } else {
+            out.writeString(this.modelId);
+        }
         if (!Objects.isNull(queryTokensSupplier) && !Objects.isNull(queryTokensSupplier.get())) {
             out.writeBoolean(true);
             out.writeMap(queryTokensSupplier.get(), StreamOutput::writeString, StreamOutput::writeFloat);
@@ -108,7 +119,9 @@ protected void doXContent(XContentBuilder xContentBuilder, Params params) throws
         xContentBuilder.startObject(NAME);
         xContentBuilder.startObject(fieldName);
         xContentBuilder.field(QUERY_TEXT_FIELD.getPreferredName(), queryText);
-        xContentBuilder.field(MODEL_ID_FIELD.getPreferredName(), modelId);
+        if (modelId != null) {
+            xContentBuilder.field(MODEL_ID_FIELD.getPreferredName(), modelId);
+        }
         printBoostAndQueryName(xContentBuilder);
         xContentBuilder.endObject();
         xContentBuilder.endObject();
@@ -152,11 +165,12 @@ public static NeuralSparseQueryBuilder fromXContent(XContentParser parser) throw
             sparseEncodingQueryBuilder.queryText(),
             String.format(Locale.ROOT, "%s field must be provided for [%s] query", QUERY_TEXT_FIELD.getPreferredName(), NAME)
         );
-        requireValue(
-            sparseEncodingQueryBuilder.modelId(),
-            String.format(Locale.ROOT, "%s field must be provided for [%s] query", MODEL_ID_FIELD.getPreferredName(), NAME)
-        );
-
+        if (!isClusterOnOrAfterMinReqVersionForDefaultModelIdSupport()) {
+            requireValue(
+                sparseEncodingQueryBuilder.modelId(),
+                String.format(Locale.ROOT, "%s field must be provided for [%s] query", MODEL_ID_FIELD.getPreferredName(), NAME)
+            );
+        }
         return sparseEncodingQueryBuilder;
     }
 
@@ -291,4 +305,8 @@ protected int doHashCode() {
     public String getWriteableName() {
         return NAME;
     }
+
+    private static boolean isClusterOnOrAfterMinReqVersionForDefaultModelIdSupport() {
+        return NeuralSearchClusterUtil.instance().getClusterMinVersion().onOrAfter(MINIMAL_SUPPORTED_VERSION_DEFAULT_MODEL_ID);
+    }
 }