Added the single embeddings provider

Author: Mikep86

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/InferencePlugin.java

@@ -99,6 +99,7 @@
 import org.elasticsearch.xpack.inference.queries.SemanticMatchQueryRewriteInterceptor;
 import org.elasticsearch.xpack.inference.queries.SemanticQueryBuilder;
 import org.elasticsearch.xpack.inference.queries.SemanticSparseVectorQueryRewriteInterceptor;
+import org.elasticsearch.xpack.inference.queries.SingleEmbeddingsProvider;
 import org.elasticsearch.xpack.inference.rank.random.RandomRankBuilder;
 import org.elasticsearch.xpack.inference.rank.random.RandomRankRetrieverBuilder;
 import org.elasticsearch.xpack.inference.rank.textsimilarity.TextSimilarityRankBuilder;
@@ -429,6 +430,9 @@ public List<NamedWriteableRegistry.Entry> getNamedWriteables() {
         entries.add(new NamedWriteableRegistry.Entry(Metadata.ProjectCustom.class, ModelRegistryMetadata.TYPE, ModelRegistryMetadata::new));
         entries.add(new NamedWriteableRegistry.Entry(NamedDiff.class, ModelRegistryMetadata.TYPE, ModelRegistryMetadata::readDiffFrom));
         entries.add(new NamedWriteableRegistry.Entry(EmbeddingsProvider.class, MapEmbeddingsProvider.NAME, MapEmbeddingsProvider::new));
+        entries.add(
+            new NamedWriteableRegistry.Entry(EmbeddingsProvider.class, SingleEmbeddingsProvider.NAME, SingleEmbeddingsProvider::new)
+        );
         return entries;
     }
 

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/queries/MapEmbeddingsProvider.java

@@ -25,7 +25,7 @@ public MapEmbeddingsProvider() {
     }
 
     public MapEmbeddingsProvider(StreamInput in) throws IOException {
-        embeddings = in.readMap(InferenceEndpointKey::new, i -> i.readNamedWriteable(InferenceResults.class));
+        this.embeddings = in.readMap(InferenceEndpointKey::new, i -> i.readNamedWriteable(InferenceResults.class));
     }
 
     @Override

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/queries/SingleEmbeddingsProvider.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.inference.queries;
+
+import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.inference.InferenceResults;
+
+import java.io.IOException;
+
+public class SingleEmbeddingsProvider implements EmbeddingsProvider {
+    public static final String NAME = "single_embeddings_provider";
+
+    private final InferenceResults embeddings;
+
+    public SingleEmbeddingsProvider(InferenceResults embeddings) {
+        this.embeddings = embeddings;
+    }
+
+    public SingleEmbeddingsProvider(StreamInput in) throws IOException {
+        this.embeddings = in.readNamedWriteable(InferenceResults.class);
+    }
+
+    @Override
+    public String getWriteableName() {
+        return NAME;
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        out.writeNamedWriteable(embeddings);
+    }
+
+    @Override
+    public InferenceResults getEmbeddings(InferenceEndpointKey key) {
+        return embeddings;
+    }
+}