SelfQueryRetriever is a retriever equipped with the capability to generate and resolve queries autonomously.
SelfQueryRetriever converts the natural language input provided by the user into a structured query using a query-constructing LLM chain . This structured query is then used to retrieve documents from the vector store .
Through this process, SelfQueryRetriever goes beyond merely comparing the user's input query with the content of stored documents semantically, and extracts filters on the metadata from the user's query and executes those filters to retrieve relevant documents.
The list of self-querying retrievers supported by LangChain can be found here.
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Sample Data
Let's build a vector store that enables similarity search based on the descriptions and metadata of some cosmetic products.
from langchain_chroma import Chroma
from langchain_core.documents import Document
from langchain_openai import OpenAIEmbeddings
# Generate sample data with the descriptions and metadata of cosmetic products.
docs = [
Document(
page_content="A hyaluronic acid serum packed with moisture, delivering hydration deep into the skin.",
metadata={"year": 2024, "category": "Skincare", "user_rating": 4.7},
),
Document(
page_content="A matte-finish foundation with 24-hour wear, covering pores and providing a natural skin appearance.",
metadata={"year": 2023, "category": "Makeup", "user_rating": 4.5},
),
Document(
page_content="A hypoallergenic cleansing oil made with plant-based ingredients, gently removes makeup and impurities.",
metadata={"year": 2023, "category": "Cleansers", "user_rating": 4.8},
),
Document(
page_content="A brightening cream with vitamin C, brightens dull skin tones for a radiant complexion.",
metadata={"year": 2023, "category": "Skincare", "user_rating": 4.6},
),
Document(
page_content="A long-lasting lipstick with vivid color payoff and a moisturizing texture for all-day comfort.",
metadata={"year": 2024, "category": "Makeup", "user_rating": 4.4},
),
Document(
page_content="A tone-up sunscreen with SPF50+/PA++++, offering high UV protection and keeping the skin safe.",
metadata={"year": 2024, "category": "Sunscreen", "user_rating": 4.9},
),
]
# Build a vector store
vectorstore = Chroma.from_documents(
docs, OpenAIEmbeddings(model="text-embedding-3-small")
)
SelfQueryRetriever
To instantiate the retriever , you need to define metadata fields and a brief description of the document contents in advance using the AttributeInfo class.
In this example, the metadata for cosmetic products is defined as follows:
category : String type, represents the category of the cosmetic product and takes one of the following values: ['Skincare', 'Makeup', 'Cleansers', 'Sunscreen'].
year : Integer type, represents the year the cosmetic product was released.
user_rating : Float type, represents the user rating in the range of 1 to 5.
from langchain.chains.query_constructor.schema import AttributeInfo
# Generate metadata field
metadata_field_info = [
AttributeInfo(
name="category",
description="The category of the cosmetic product. One of ['Skincare', 'Makeup', 'Cleansers', 'Sunscreen']",
type="string",
),
AttributeInfo(
name="year",
description="The year the cosmetic product was released",
type="integer",
),
AttributeInfo(
name="user_rating",
description="A user rating for the cosmetic product, ranging from 1 to 5",
type="float",
),
]
Create retriever object with SelfQueryRetriever.from_llm method.
llm: Large language model
vectorstore: Vector store
document_contents: Description of the contents of the documents
metadata_field_info: Metadata field information
from langchain.retrievers.self_query.base import SelfQueryRetriever
from langchain_openai import ChatOpenAI
# Define the LLM to use
llm = ChatOpenAI(model="gpt-4o-mini", temperature=0)
# Create SelfQueryRetriever
retriever = SelfQueryRetriever.from_llm(
llm=llm,
vectorstore=vectorstore,
document_contents="Brief summary of a cosmetic product",
metadata_field_info=metadata_field_info,
)
Now, let's test this SelfQueryRetriever with some example queries.
# Self-query retrieval
retriever.invoke("Please recommend products with a rating of 4.8 or higher.")
[Document(metadata={'category': 'Cleansers', 'user_rating': 4.8, 'year': 2023}, page_content='A hypoallergenic cleansing oil made with plant-based ingredients, gently removes makeup and impurities.'),
Document(metadata={'category': 'Sunscreen', 'user_rating': 4.9, 'year': 2024}, page_content='A tone-up sunscreen with SPF50+/PA++++, offering high UV protection and keeping the skin safe.')]
# Self-query retrieval
retriever.invoke("Please recommend products released in 2023.")
[Document(metadata={'category': 'Cleansers', 'user_rating': 4.8, 'year': 2023}, page_content='A hypoallergenic cleansing oil made with plant-based ingredients, gently removes makeup and impurities.'),
Document(metadata={'category': 'Skincare', 'user_rating': 4.6, 'year': 2023}, page_content='A brightening cream with vitamin C, brightens dull skin tones for a radiant complexion.'),
Document(metadata={'category': 'Makeup', 'user_rating': 4.5, 'year': 2023}, page_content='A matte-finish foundation with 24-hour wear, covering pores and providing a natural skin appearance.')]
# Self-query retrieval
retriever.invoke("Please recommend products in the Sunscreen category.")
[Document(metadata={'category': 'Sunscreen', 'user_rating': 4.9, 'year': 2024}, page_content='A tone-up sunscreen with SPF50+/PA++++, offering high UV protection and keeping the skin safe.')]
SelfQueryRetriever can also be used to retrieve items with two or more conditions.
# Self-query retrieval
retriever.invoke(
"Please recommend products in the 'Makeup' category with a rating of 4.5 or higher."
)
[Document(metadata={'category': 'Makeup', 'user_rating': 4.5, 'year': 2023}, page_content='A matte-finish foundation with 24-hour wear, covering pores and providing a natural skin appearance.')]
You can also specify the number of documents to retrieve using the argument k when using SelfQueryRetriever .
This can be done by passing enable_limit=True to the constructor.
retriever = SelfQueryRetriever.from_llm(
llm=llm,
vectorstore=vectorstore,
document_contents="Brief summary of a cosmetic product",
metadata_field_info=metadata_field_info,
enable_limit=True, # Enable to limit the search result.
search_kwargs={"k": 2}, # Limit the number of retrieved documents to 2.
)
There are 3 products released in 2023, but by setting the value of k to 2, only 2 products are retrieved.
# Self-query retrieval
retriever.invoke("Please recommend products released in 2023.")
[Document(metadata={'category': 'Cleansers', 'user_rating': 4.8, 'year': 2023}, page_content='A hypoallergenic cleansing oil made with plant-based ingredients, gently removes makeup and impurities.'),
Document(metadata={'category': 'Skincare', 'user_rating': 4.6, 'year': 2023}, page_content='A brightening cream with vitamin C, brightens dull skin tones for a radiant complexion.')]
However, you can also limit the number of search results by directly specifying the number of search results in the query without explicitly specifying search_kwargs in the code.
retriever = SelfQueryRetriever.from_llm(
llm=llm,
vectorstore=vectorstore,
document_contents="Brief summary of a cosmetic product",
metadata_field_info=metadata_field_info,
enable_limit=True, # Enable to limit the search result.
)
# Self-query retrieval
retriever.invoke("Please recommend one product released in 2023.")
[Document(metadata={'category': 'Cleansers', 'user_rating': 4.8, 'year': 2023}, page_content='A hypoallergenic cleansing oil made with plant-based ingredients, gently removes makeup and impurities.')]
# Self-query retrieval
retriever.invoke("Please recommend 2 products released in 2023.")
[Document(metadata={'category': 'Cleansers', 'user_rating': 4.8, 'year': 2023}, page_content='A hypoallergenic cleansing oil made with plant-based ingredients, gently removes makeup and impurities.'),
Document(metadata={'category': 'Skincare', 'user_rating': 4.6, 'year': 2023}, page_content='A brightening cream with vitamin C, brightens dull skin tones for a radiant complexion.')]
Query Constructor Chain
To see what happens internally and to have more custom control, we can construct a retriever from scratch.
First, we need to create a query_constructor chain that generates structured queries. Here, we use the get_query_constructor_prompt function to retrieve the prompt that helps constructing queries.
from langchain.chains.query_constructor.base import (
StructuredQueryOutputParser,
get_query_constructor_prompt,
)
# Retrieve the query constructor prompt using the document content description and metadata field information.
prompt = get_query_constructor_prompt(
"Brief summary of a cosmetic product", # Document content description
metadata_field_info, # Metadata field information
)
# Create StructuredQueryOutputParser
output_parser = StructuredQueryOutputParser.from_components()
# Create query_constructor chain
query_constructor = prompt | llm | output_parser
To check the content of the prompt, use the prompt.format method to pass the string "dummy question" to the query parameter and print the result.
Your goal is to structure the user's query to match the request schema provided below.
<< Structured Request Schema >>
When responding use a markdown code snippet with a JSON object formatted in the following schema:
```json
{
"query": string \ text string to compare to document contents
"filter": string \ logical condition statement for filtering documents
}
```
The query string should contain only text that is expected to match the contents of documents. Any conditions in the filter should not be mentioned in the query as well.
A logical condition statement is composed of one or more comparison and logical operation statements.
A comparison statement takes the form: `comp(attr, val)`:
- `comp` (eq | ne | gt | gte | lt | lte | contain | like | in | nin): comparator
- `attr` (string): name of attribute to apply the comparison to
- `val` (string): is the comparison value
A logical operation statement takes the form `op(statement1, statement2, ...)`:
- `op` (and | or | not): logical operator
- `statement1`, `statement2`, ... (comparison statements or logical operation statements): one or more statements to apply the operation to
Make sure that you only use the comparators and logical operators listed above and no others.
Make sure that filters only refer to attributes that exist in the data source.
Make sure that filters only use the attributed names with its function names if there are functions applied on them.
Make sure that filters only use format `YYYY-MM-DD` when handling date data typed values.
Make sure that filters take into account the descriptions of attributes and only make comparisons that are feasible given the type of data being stored.
Make sure that filters are only used as needed. If there are no filters that should be applied return "NO_FILTER" for the filter value.
<< Example 1. >>
Data Source:
```json
{
"content": "Lyrics of a song",
"attributes": {
"artist": {
"type": "string",
"description": "Name of the song artist"
},
"length": {
"type": "integer",
"description": "Length of the song in seconds"
},
"genre": {
"type": "string",
"description": "The song genre, one of "pop", "rock" or "rap""
}
}
}
```
User Query:
What are songs by Taylor Swift or Katy Perry about teenage romance under 3 minutes long in the dance pop genre
Structured Request:
```json
{
"query": "teenager love",
"filter": "and(or(eq(\"artist\", \"Taylor Swift\"), eq(\"artist\", \"Katy Perry\")), lt(\"length\", 180), eq(\"genre\", \"pop\"))"
}
```
<< Example 2. >>
Data Source:
```json
{
"content": "Lyrics of a song",
"attributes": {
"artist": {
"type": "string",
"description": "Name of the song artist"
},
"length": {
"type": "integer",
"description": "Length of the song in seconds"
},
"genre": {
"type": "string",
"description": "The song genre, one of "pop", "rock" or "rap""
}
}
}
```
User Query:
What are songs that were not published on Spotify
Structured Request:
```json
{
"query": "",
"filter": "NO_FILTER"
}
```
<< Example 3. >>
Data Source:
```json
{
"content": "Brief summary of a cosmetic product",
"attributes": {
"category": {
"description": "The category of the cosmetic product. One of ['Skincare', 'Makeup', 'Cleansers', 'Sunscreen']",
"type": "string"
},
"year": {
"description": "The year the cosmetic product was released",
"type": "integer"
},
"user_rating": {
"description": "A user rating for the cosmetic product, ranging from 1 to 5",
"type": "float"
}
}
}
```
User Query:
dummy question
Structured Request:
Call the query_constructor.invoke method to process the given query.
query_output = query_constructor.invoke(
{
# Call the query constructor to generate a query.
"query": "Please recommend skincare products released in 2023 with a rating of 4.5 or higher."
}
)
The core component of a SelfQueryRetriever is the query constructor . To build an effective retrieval system, it is essential to ensure that the query constructor is well defined.
To achieve this, you need to adjust the prompt, examples within the prompt, and attribute descriptions .
Structured Query Translator
You can also create a structured query using the structured query translator .
Structured query translator converts a query into metadata filters compatible with the syntax of the vector store with StructuredQuery object.
from langchain.retrievers.self_query.chroma import ChromaTranslator
retriever = SelfQueryRetriever(
query_constructor=query_constructor, # The query_constructor chain created in the previous step.
vectorstore=vectorstore, # Specify the VectorStore
structured_query_translator=ChromaTranslator(), # Query translator
)
Use the retriever.invoke method to generate an answer for the given question.
retriever.invoke(
"Please recommend skincare products released in 2023 with a rating of 4.5 or higher."
)
[Document(metadata={'category': 'Skincare', 'user_rating': 4.7, 'year': 2024}, page_content='A hyaluronic acid serum packed with moisture, delivering hydration deep into the skin.'),
Document(metadata={'category': 'Skincare', 'user_rating': 4.6, 'year': 2023}, page_content='A brightening cream with vitamin C, brightens dull skin tones for a radiant complexion.')]
