Overlap and chunk boundaries in LangChain

Introduction

We split large texts into smaller parts called chunks to handle them easily. Overlap helps keep some shared words between chunks so we don't lose important connections.

When processing long documents that don't fit in memory all at once.

When you want to keep context between parts of a text for better understanding.

When preparing text for search or question-answering systems.

When you want to avoid cutting sentences or ideas abruptly.

When feeding text into models with input size limits.

Syntax

LangChain

text_splitter = RecursiveCharacterTextSplitter(chunk_size=1000, chunk_overlap=200)
chunks = text_splitter.split_text(long_text)

chunk_size sets how big each chunk is.

chunk_overlap sets how many characters repeat between chunks.

Examples

This splits text into 500-character chunks with 50 characters repeated between chunks.

LangChain

text_splitter = RecursiveCharacterTextSplitter(chunk_size=500, chunk_overlap=50)
chunks = text_splitter.split_text(long_text)

This splits text into 1000-character chunks with no overlap, so chunks are separate.

LangChain

text_splitter = RecursiveCharacterTextSplitter(chunk_size=1000, chunk_overlap=0)
chunks = text_splitter.split_text(long_text)

Sample Program

This example creates a long repeated text. It splits it into chunks of 100 characters each, with 20 characters overlapping between chunks. It prints the first 3 chunks to show how overlap works.

LangChain

from langchain.text_splitter import RecursiveCharacterTextSplitter

long_text = """LangChain helps you build applications with language models. """ * 50

text_splitter = RecursiveCharacterTextSplitter(chunk_size=100, chunk_overlap=20)
chunks = text_splitter.split_text(long_text)

for i, chunk in enumerate(chunks[:3]):
    print(f"Chunk {i+1} (length {len(chunk)}):")
    print(chunk)
    print('---')

Important Notes

Overlap helps keep context between chunks but increases total text size.

Too much overlap can slow down processing, so choose a balance.

Chunk boundaries try to split at natural breaks like spaces or punctuation.

Summary

Chunking breaks big text into smaller pieces for easier handling.

Overlap repeats some text between chunks to keep context.

Use LangChain's RecursiveCharacterTextSplitter to control chunk size and overlap.