From LangChain to Enterprise Applications: Best Practices for Fixed-Size Chunking in RAG

Written by
Clara Bennett
Updated on:June-13th-2025
Recommendation

Explore the practice and application of the fixed-size chunking strategy in the RAG architecture, and reveal the efficient implementation of Fixed-Size Chunking in enterprise-level AI scenarios.

Core content:
1. The core logic and implementation of the Fixed-Size Chunking strategy
2. The application scenarios and advantages of fixed chunking in the RAG system
3. Analysis of common misunderstandings and guidance on best practices

Yang Fangxian
Founder of 53A/Most Valuable Expert of Tencent Cloud (TVP)

     As we all know, in the process of building a RAG (Retrieval-Augmented Generation) system, the document segmentation strategy often determines the upper limit of the model's retrieval quality. If the segmentation is good, the information hit is more accurate and the generated answer has more contextual logic; if the segmentation is bad, the model is likely to "answer the wrong question".
    Among the many strategies, Fixed-Size Chunking is the simplest and most direct, but also the most often overlooked. It may seem crude, but it performs stably and has wide adaptability in actual projects, especially for scenarios that are sensitive to real-time response and cost.
     So, how should Fixed-Size Chunking be set up? What are some common misunderstandings? Is it really "simple and effective"? This article will take you through the core logic, code implementation, and applicable scenarios of the fixed-size chunking strategy, so that you can avoid pitfalls and improve efficiency when building RAG applications.

0 1 

How to understand  Fixed-Size Chunking?

     In the Retrieval Augmented Generation (RAG) system, document chunking is the first key step that affects retrieval efficiency and generation quality. Therefore, in actual business scenarios, it is crucial to understand and choose an appropriate chunking strategy.
     However, as the most basic and intuitive chunking method among the nine chunking strategies, Fixed-Size Chunking has a wider range of application scenarios and plays an important role.
     The core idea of ​​the Fixed-Size Chunking strategy is to mechanically divide long text content into preset, unified length units. This length unit can be the number of words (word count), the number of characters (character count), or the number of tokens (token count) input to the model.
    For example, we can split a lengthy document into independent text blocks every 200 words or 512 tokens. This method relies entirely on direct and programmatic text segmentation logic, without involving complex semantic analysis or linguistic judgment. It is particularly suitable for scenarios where downstream models or systems have strict fixed size requirements for input data, such as batch processing or fixed-dimensional input to certain machine learning models.

0 2 

What are the advantages and disadvantages of the Fixed-Size Chunking strategy?

     In actual business scenarios, the fixed -size chunking strategy has great advantages, as shown in the following two points:

     1. Simplicity and Speed

     The implementation logic of the fixed-size segmentation strategy is extremely intuitive and simple, and does not require complex linguistic analysis, deep learning model support, or advanced algorithm support. This makes it extremely low in resource consumption during the development and deployment phase, and can complete large-scale text segmentation tasks at a very high speed. It is the preferred strategy for quickly building RAG prototypes or processing massive unstructured data.

     2. High predictability and data uniformity

     In addition, this strategy can produce text blocks with uniform size and consistent format. This high degree of predictability greatly simplifies the storage, indexing, and retrieval of data in the subsequent RAG process. For example, in a vector database, the dimensions and storage space of all text blocks are predictable, which is conducive to database performance optimization, resource management, and system debugging.

     Although the fixed -size chunking strategy is widely used in actual scenarios, it faces the following problems as the business becomes more complex:

     One is context fragmentation, that is, because the segmentation is mechanical, it often forces segmentation in the middle of sentences, at the junction of paragraphs, or even inside important logical units (such as list items and key definitions). This semantic fragmentation will seriously undermine the natural semantic flow and contextual coherence of the text.

     During retrieval, the large model may obtain incomplete or fragmented context information, which may lead to misunderstanding, affect the accuracy of the answer, and even produce "hallucinations". This is also the most significant disadvantage of fixed-size segmentation.

    The second problem is the lack of adaptability and rigidity, because this method cannot make adaptive adjustments based on the logical structure, semantic boundaries, topic changes, or complexity of the document.

     Important related concepts or information may be unnecessarily split into different chunks, or irrelevant contexts may be forcibly bundled together. This rigidity makes it often unsatisfactory in retrieval and generation when dealing with documents with complex structures, close semantic connections, or containing multiple topics.

0 3 

Fixed-Size Chunking Strategy Simple Implementation Example Analysis

     Next, let's look at a simple example based on Python code to implement how to segment text according to a fixed number of words. The details are as follows:
def fixed_size_chunk(text: str, chunk_size: int = 50) -> list[str]: """ Split text into fixed words. Args: text (str): The original text string to be split. chunk_size (int): The number of words each text chunk contains. Default is 50 words. Returns: list[str]: A list of strings containing the split text chunks. """ words = text.split() chunks = [" ".join(words[i:i+chunk_size]) for i in range(0, len(words), chunk_size)] return chunks # --- Example Usage --- # Assume pdf_text_example is a long text content extracted from a PDF document # For demonstration, I will use a sufficiently long example text, but you can replace it with your actual text pdf_text_example = """In the field of artificial intelligence, retrieval-augmented generation (RAG) technology has become a core paradigm for building practical, knowledge-driven large-scale language model (LLM) applications. It effectively bridges the gap between static knowledge in the model and dynamic external information, allowing LLM to reference real-time or domain-specific data, greatly improving the accuracy and reliability of responses. However, as we move towards more complex AI applications, relying solely on vector similarity search often seems to be inadequate when dealing with data that is interrelated and where relationships are critical. Building truly intelligent agents or providing highly accurate and contextually informed responses requires understanding the 'connections' between information, not just the 'similarities'. This is exactly what is needed for the next generation of RAG applications. The database that supports these advanced capabilities must be able to handle both vector similarity and complex structured relationships. HelixDB was born to meet this challenge. It breaks the boundaries of traditional databases and is a revolutionary open source graph vector database that cleverly combines the powerful relational expression capabilities of graph databases with the efficient similarity search capabilities of vector databases. HelixDB is designed to power the next generation of RAG Applications provide a smarter and more flexible data storage foundation, allowing you to perform richer contextual retrieval based on content similarity and structured relationships. If you are exploring the future of RAG and looking for a powerful open source data solution that can handle both vectors and complex relationships, it is important to understand HelixDB. Through this article, you will understand the core concept, architectural advantages, and how it can help your intelligent innovation of this open source graph vector database tailored for the next generation of RAG applications. Let's take a deeper look at the uniqueness of HelixDB! This is an extra sentence to ensure that the text is long enough to be split into multiple chunks to demonstrate the printing of the second chunk. """# Split the text into chunks of 50 words chunks_result = fixed_size_chunk(pdf_text_example, chunk_size=10)print(f"The original text was split into {len(chunks_result)} chunks."")# --- The solution is here: add a safety check ---# Try to print the first chunkif len(chunks_result) > 0: print("\n--- Example of the first chunk content ---") print(chunks_result[0])else: print("\n--- List is empty, can't print first chunk ---")# Try to print second chunk, check if list length is at least 2 elements firstif len(chunks_result) > 1: print("\n--- Example of second chunk contents ---") print(chunks_result[1])else: print("\n--- Can't print second chunk because list is not long enough (less than 2 chunks) ---")# If you want to print all generated chunks, you can use a loop:# print("\n--- All generated chunks of text ---")# for i, chunk in enumerate(chunks_result):# print(f"chunk {i}:")# print(chunk)# print("-" * 20)
    The above code implements a fixed-size chunking function, which is used to split a long text into multiple chunks according to the specified number of words. It is suitable for document preprocessing in the RAG (Retrieval-Augmented Generation) system.
    Execute the run:
[(base) lugalee @labs  rag ] %  /opt/ homebrew /bin/ python3  /Volumes/ home /rag/ fixedsiz.pyThe original text is split into  2  blocks .
---  First block content example  ---In the field of artificial intelligence, retrieval-augmented generation ( RAG) technology has become a core paradigm for building practical , knowledge-driven large language model ( LLM) applications . It effectively bridges the gap between static knowledge in the model and dynamic external information, allowing  LLM  to reference real-time or domain-specific data, greatly improving the accuracy and reliability of responses . However, as we move towards more complex  AI  applications, relying solely on vector similarity search often seems to be inadequate when dealing with data that is interrelated and where relationships are critical . Building truly intelligent agents or providing highly accurate and context-sensitive answers requires understanding the 'connections' between information, not just the 'similarities' . This is exactly  what is needed for the next generation  of RAG applications . The database that supports these advanced capabilities must be able to handle both vector similarity and complex structured relationships . HelixDB  came into being to meet this challenge . It breaks the boundaries of traditional databases and is a revolutionary open source graph vector database that cleverly combines the powerful relational expression capabilities of graph databases with the efficient similarity search capabilities of vector databases . HelixDB  is designed to power the next generation  of RAG
---  Second block content example  ---The application provides a smarter and more flexible data storage foundation, allowing you to perform richer contextual retrieval based on content similarity and structured relationships . If you are exploring  the future of RAG  and looking for a powerful open source data solution that can handle both vectors and complex relationships, then understanding  HelixDB  is essential . Through this article, you will understand the core concepts , architectural advantages, and how this   open source graph vector database tailored for the next generation of RAG applications can help you innovate intelligently . Let's take a deeper look at   the uniqueness of HelixDB !
     That’s all for today’s analysis. For more  in-depth analysis of LM Studio-related technologies, best practices, and related technology frontiers, please follow our WeChat public account or video account: Architecture Station (priest-arc) to get more exclusive technical insights!

  ···········