如何查看LangChain中Chroma存储的文档Embedding？为何返回None？

执行db.get()后，返回结果中的embeddings字段始终为None，但文档内容、元数据等其他内容均正常显示。

已做的验证测试 #

• 单独验证embeddings组件功能正常，执行以下代码返回向量长度为1536：

len(embeddings.embed_documents(["EMBED THIS"])[0])
>> 1536

• 本地./data目录下存在chroma-embeddings.parquet文件

官方示例代码复现问题 #

即使使用官方示例代码创建Chroma实例，执行new_db.get()后，embeddings字段仍为None：

# Import Document class
from langchain.docstore.document import Document

# Initial document content and id
initial_content = "This is an initial document content"
document_id = "doc1"

# Create an instance of Document with initial content and metadata
original_doc = Document(page_content=initial_content, metadata={"page": "0"})

# Initialize a Chroma instance with the original document
new_db = Chroma.from_documents(
    collection_name="test_collection",
    documents=[original_doc],
    embedding=OpenAIEmbeddings(),  # using the same embeddings as before
    ids=[document_id],
)

我的核心代码 #

for db_collection_name in tqdm(["class1-sub2-chap3", "class2-sub3-chap4"]):
    documents = []
    doc_ids = []

    for doc_index in range(3):
        cl, sub, chap = db_collection_name.split("-")
        content = f"This is {db_collection_name}-doc{doc_index}"
        doc = Document(page_content=content, metadata={"chunk_num": doc_index, "chapter":chap, "class":cl, "subject":sub})
        documents.append(doc)
        doc_ids.append(str(doc_index))


    # Initialize a Chroma instance with the original document
    db = Chroma.from_documents(
         collection_name=db_collection_name,
         documents=documents, ids=doc_ids,
         embedding=embeddings, 
         persist_directory="./data")
     
     db.persist()

执行db.get()的返回结果示例 #

{'ids': ['0', '1', '2'],
 'embeddings': None,
 'documents': ['This is class1-sub2-chap3-doc0',
  'This is class1-sub2-chap3-doc1',
  'This is class1-sub2-chap3-doc2'],
 'metadatas': [{'chunk_num': 0,
   'chapter': 'chap3',
   'class': 'class1',
   'subject': 'sub2'},
  {'chunk_num': 1, 'chapter': 'chap3', 'class': 'class1', 'subject': 'sub2'},
  {'chunk_num': 2, 'chapter': 'chap3', 'class': 'class1', 'subject': 'sub2'}]}

内容的提问来源于stack exchange，提问作者Deshwal