RecursiveCharacterTextSplitter未生成chunk overlap的原因及疑问

你的猜测是对的——重叠部分必须在指定的分隔符位置拆分，而且只有当文本块的拆分逻辑触发重叠截取条件时，才会产生chunk_overlap。

具体原因： #

• RecursiveCharacterTextSplitter是按你指定的分隔符优先级（\n\n > \n > 句点后空格 > 空格 > 无分隔符）递归拆分文本的。你的测试文本刚好被最高优先级的\n\n拆成了两个独立段落，第一个段落长度248，第二个243，都远小于设置的chunk_size=350。
• 这个拆分器的核心逻辑是：如果当前待处理的文本段长度小于chunk_size，就直接将其作为一个完整块保留，不会触发重叠截取操作。只有当某个文本段长度超过chunk_size时，才会继续拆分，并且生成下一个块时，从上个块的末尾（必须落在分隔符位置）往前截取chunk_overlap长度的内容作为重叠部分。
• 你设置的100字符重叠，只有当拆分后的块接近或超过350字符时才会生效。比如如果第一个段落长度是400（超过chunk_size），拆分后第二个块会从第一个块末尾往前100字符（且在最近的分隔符处）开始截取，这样才会产生重叠。

测试代码： #

from langchain.text_splitter import RecursiveCharacterTextSplitter

some_text = """When writing documents, writers will use document structure to group content. \nThis can convey to the reader, which idea's are related. For example, closely related ideas \nare in sentances. Similar ideas are in paragraphs. Paragraphs form a document. \n\n  \nParagraphs are often delimited with a carriage return or two carriage returns. \nCarriage returns are the "backslash n" you see embedded in this string. \nSentences have a period at the end, but also, have a space.\nand words are separated by space."""

r_splitter = RecursiveCharacterTextSplitter(
    chunk_size=350,
    chunk_overlap=100,
    separators=["\n\n", "\n", "(?<=\\. )", " ", ""]
)
x = r_splitter.split_text(some_text)
print(x)
for thing in x:
    print(len(thing))

输出结果： #

["When writing documents, writers will use document structure to group content. This can convey to the reader, which idea's are related. For example, closely related ideas are in sentances. Similar ideas are in paragraphs. Paragraphs form a document.", 
'Paragraphs are often delimited with a carriage return or two carriage returns. Carriage returns are the "backslash n" you see embedded in this string. Sentences have a period at the end, but also, have a space.and words are separated by space.']
248
243

内容的提问来源于stack exchange，提问作者codeananda