mirror of
https://github.com/hwchase17/langchain
synced 2024-11-02 09:40:22 +00:00
92 lines
2.9 KiB
Python
92 lines
2.9 KiB
Python
"""Cassandra-based chat message history, based on cassIO."""
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from __future__ import annotations
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import json
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import uuid
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from typing import TYPE_CHECKING, List, Optional
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if TYPE_CHECKING:
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from cassandra.cluster import Session
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from langchain_core.chat_history import BaseChatMessageHistory
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from langchain_core.messages import (
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BaseMessage,
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message_to_dict,
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messages_from_dict,
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)
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DEFAULT_TABLE_NAME = "message_store"
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DEFAULT_TTL_SECONDS = None
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class CassandraChatMessageHistory(BaseChatMessageHistory):
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"""Chat message history that stores history in Cassandra.
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Args:
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session_id: arbitrary key that is used to store the messages
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of a single chat session.
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session: Cassandra driver session. If not provided, it is resolved from cassio.
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keyspace: Cassandra key space. If not provided, it is resolved from cassio.
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table_name: name of the table to use.
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ttl_seconds: time-to-live (seconds) for automatic expiration
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of stored entries. None (default) for no expiration.
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"""
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def __init__(
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self,
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session_id: str,
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session: Optional[Session] = None,
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keyspace: Optional[str] = None,
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table_name: str = DEFAULT_TABLE_NAME,
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ttl_seconds: Optional[int] = DEFAULT_TTL_SECONDS,
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) -> None:
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try:
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from cassio.table import ClusteredCassandraTable
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except (ImportError, ModuleNotFoundError):
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raise ImportError(
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"Could not import cassio python package. "
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"Please install it with `pip install cassio`."
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)
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self.session_id = session_id
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self.ttl_seconds = ttl_seconds
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self.table = ClusteredCassandraTable(
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session=session,
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keyspace=keyspace,
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table=table_name,
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ttl_seconds=ttl_seconds,
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primary_key_type=["TEXT", "TIMEUUID"],
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ordering_in_partition="DESC",
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)
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@property
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def messages(self) -> List[BaseMessage]: # type: ignore
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"""Retrieve all session messages from DB"""
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# The latest are returned, in chronological order
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message_blobs = [
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row["body_blob"]
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for row in self.table.get_partition(
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partition_id=self.session_id,
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)
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][::-1]
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items = [json.loads(message_blob) for message_blob in message_blobs]
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messages = messages_from_dict(items)
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return messages
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def add_message(self, message: BaseMessage) -> None:
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"""Write a message to the table
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Args:
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message: A message to write.
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"""
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this_row_id = uuid.uuid1()
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self.table.put(
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partition_id=self.session_id,
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row_id=this_row_id,
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body_blob=json.dumps(message_to_dict(message)),
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ttl_seconds=self.ttl_seconds,
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)
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def clear(self) -> None:
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"""Clear session memory from DB"""
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self.table.delete_partition(self.session_id)
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