Support Embedding for Large Amounts of Texts (#1142)

fix: #1140

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## Issue
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## Change
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## General checklist
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## Checklist for adding new model integration
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- [ ] I have added my new module in the
[BOM](https://github.com/langchain4j/langchain4j/blob/main/langchain4j-bom/pom.xml)


## Checklist for adding new embedding store integration
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- [ ] I have added a `{NameOfIntegration}EmbeddingStoreIT` that extends
from either `EmbeddingStoreIT` or `EmbeddingStoreWithFilteringIT`
- [ ] I have added my new module in the
[BOM](https://github.com/langchain4j/langchain4j/blob/main/langchain4j-bom/pom.xml)


## Checklist for changing existing embedding store integration
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[X] -->
- [ ] I have manually verified that the
`{NameOfIntegration}EmbeddingStore` works correctly with the data
persisted using the latest released version of LangChain4j

langchain4j-dashscope/src/main/java/dev/langchain4j/model/dashscope/QwenEmbeddingModel.java

@@ -24,6 +24,7 @@ public class QwenEmbeddingModel implements EmbeddingModel {
     public static final String TYPE_KEY = "type";
     public static final String TYPE_QUERY = "query";
     public static final String TYPE_DOCUMENT = "document";
+    private static final int MAX_BATCH_SIZE = 25;
 
     private final String apiKey;
     private final String modelName;
@@ -53,7 +54,30 @@ public class QwenEmbeddingModel implements EmbeddingModel {
                 .anyMatch(TYPE_QUERY::equalsIgnoreCase);
     }
 
-    private Response<List<Embedding>> embedTexts(List<TextSegment> textSegments, TextEmbeddingParam.TextType textType) {
+    private Response<List<Embedding>> embedTexts(List<TextSegment> textSegments,
+                                                 TextEmbeddingParam.TextType textType) {
+        int size = textSegments.size();
+        if (size < MAX_BATCH_SIZE) {
+            return batchEmbedTexts(textSegments, textType);
+        }
+
+        List<Embedding> allEmbeddings = new ArrayList<>(size);
+        TokenUsage allUsage = null;
+        int fromIndex = 0;
+        int toIndex = MAX_BATCH_SIZE;
+        while (fromIndex < size) {
+            List<TextSegment> batchTextSegments = textSegments.subList(fromIndex, toIndex);
+            Response<List<Embedding>> batchResponse = batchEmbedTexts(batchTextSegments, textType);
+            allEmbeddings.addAll(batchResponse.content());
+            allUsage = TokenUsage.sum(allUsage, batchResponse.tokenUsage());
+            fromIndex = toIndex;
+            toIndex = Math.min(size, fromIndex + MAX_BATCH_SIZE);
+        }
+
+        return Response.from(allEmbeddings, allUsage);
+    }
+
+    private Response<List<Embedding>> batchEmbedTexts(List<TextSegment> textSegments, TextEmbeddingParam.TextType textType) {
         TextEmbeddingParam param = TextEmbeddingParam.builder()
                 .apiKey(apiKey)
                 .model(modelName)

langchain4j-dashscope/src/test/java/dev/langchain4j/model/dashscope/QwenEmbeddingModelIT.java

@@ -7,9 +7,14 @@ import org.junit.jupiter.api.condition.EnabledIfEnvironmentVariable;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.MethodSource;
 
+import java.util.Collections;
 import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import static dev.langchain4j.data.segment.TextSegment.textSegment;
+import static dev.langchain4j.model.dashscope.QwenEmbeddingModel.TYPE_KEY;
+import static dev.langchain4j.model.dashscope.QwenEmbeddingModel.TYPE_QUERY;
 import static dev.langchain4j.model.dashscope.QwenTestHelper.apiKey;
 import static java.util.Arrays.asList;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -52,8 +57,8 @@ public class QwenEmbeddingModelIT {
     void should_embed_queries(String modelName) {
         EmbeddingModel model = getModel(modelName);
         List<Embedding> embeddings = model.embedAll(asList(
-                textSegment("hello", Metadata.from(QwenEmbeddingModel.TYPE_KEY, QwenEmbeddingModel.TYPE_QUERY)),
+                textSegment("hello", Metadata.from(TYPE_KEY, TYPE_QUERY)),
-                textSegment("how are you?", Metadata.from(QwenEmbeddingModel.TYPE_KEY, QwenEmbeddingModel.TYPE_QUERY))
+                textSegment("how are you?", Metadata.from(TYPE_KEY, TYPE_QUERY))
         )).content();
 
         assertThat(embeddings).hasSize(2);
@@ -66,7 +71,7 @@ public class QwenEmbeddingModelIT {
     void should_embed_mix_segments(String modelName) {
         EmbeddingModel model = getModel(modelName);
         List<Embedding> embeddings = model.embedAll(asList(
-                textSegment("hello", Metadata.from(QwenEmbeddingModel.TYPE_KEY, QwenEmbeddingModel.TYPE_QUERY)),
+                textSegment("hello", Metadata.from(TYPE_KEY, TYPE_QUERY)),
                 textSegment("how are you?")
         )).content();
 
@@ -74,4 +79,39 @@ public class QwenEmbeddingModelIT {
         assertThat(embeddings.get(0).vector()).isNotEmpty();
         assertThat(embeddings.get(1).vector()).isNotEmpty();
     }
+
+    @ParameterizedTest
+    @MethodSource("dev.langchain4j.model.dashscope.QwenTestHelper#embeddingModelNameProvider")
+    void should_embed_large_amounts_of_documents(String modelName) {
+        EmbeddingModel model = getModel(modelName);
+        List<Embedding> embeddings = model.embedAll(
+                Collections.nCopies(50, textSegment("hello"))).content();
+
+        assertThat(embeddings).hasSize(50);
+    }
+
+    @ParameterizedTest
+    @MethodSource("dev.langchain4j.model.dashscope.QwenTestHelper#embeddingModelNameProvider")
+    void should_embed_large_amounts_of_queries(String modelName) {
+        EmbeddingModel model = getModel(modelName);
+        List<Embedding> embeddings = model.embedAll(
+                Collections.nCopies(50, textSegment("hello", Metadata.from(TYPE_KEY, TYPE_QUERY)))
+        ).content();
+
+        assertThat(embeddings).hasSize(50);
+    }
+
+    @ParameterizedTest
+    @MethodSource("dev.langchain4j.model.dashscope.QwenTestHelper#embeddingModelNameProvider")
+    void should_embed_large_amounts_of_mix_segments(String modelName) {
+        EmbeddingModel model = getModel(modelName);
+        List<Embedding> embeddings = model.embedAll(
+                Stream.concat(
+                        Collections.nCopies(50, textSegment("hello", Metadata.from(TYPE_KEY, TYPE_QUERY))).stream(),
+                        Collections.nCopies(50, textSegment("how are you?")).stream()
+                ).collect(Collectors.toList())
+        ).content();
+
+        assertThat(embeddings).hasSize(100);
+    }
 }