PostgresChatMessageHistory message order isn't guaranteed

[mattflo]

System Info

Langchain version: 0.0.208
OS version: macOS 13.4
Python version: 3.10.12

Who can help?

@hwchase17

Information

• The official example notebooks/scripts
• My own modified scripts

Related Components

• LLMs/Chat Models
• Embedding Models
• Prompts / Prompt Templates / Prompt Selectors
• Output Parsers
• Document Loaders
• Vector Stores / Retrievers
• Memory
• Agents / Agent Executors
• Tools / Toolkits
• Chains
• Callbacks/Tracing
• Async

Reproduction

Queries without an order by clause aren't guaranteed to have any particular order.

Expected behavior

Chat history should be in order.

[dosubot]

Answer generated by a 🤖

Answer

To ensure that the chat history is ordered, you can modify the messages property in the PostgresChatMessageHistory class to include an ORDER BY clause in the SQL query. You can order the messages by their id to maintain the order in which they were added to the database.

Here's the updated messages property:

@property
def messages(self) -> List[BaseMessage]:  # type: ignore
    """Retrieve the messages from PostgreSQL"""
    query = f"SELECT message FROM {self.table_name} WHERE session_id = %s ORDER BY id;"
    self.cursor.execute(query, (self.session_id,))
    items = [record["message"] for record in self.cursor.fetchall()]
    messages = messages_from_dict(items)
    return messages

This change will ensure that the chat history is returned in the order of the id column, which should maintain the order in which the messages were added.

Sources

• docs/extras/modules/memory/integrations/postgres_chat_message_history.ipynb
• langchain/memory/chat_message_histories/postgres.py
• tests/unit_tests/memory/chat_message_histories/test_sql.py

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