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import logging
from typing import Any, List, Dict
from langchain.memory.chat_memory import BaseChatMemory
from langchain.schema import get_buffer_string, BaseMessage, HumanMessage, AIMessage
from langchain.schema.language_model import BaseLanguageModel
from server.db.repository.message_repository import filter_message
from server.db.models.message_model import MessageModel
class ConversationBufferDBMemory(BaseChatMemory):
conversation_id: str
human_prefix: str = "Human"
ai_prefix: str = "Assistant"
llm: BaseLanguageModel
memory_key: str = "history"
max_token_limit: int = 2000
message_limit: int = 10
@property
def buffer(self) -> List[BaseMessage]:
"""String buffer of memory."""
# fetch limited messages desc, and return reversed
messages = filter_message(conversation_id=self.conversation_id, limit=self.message_limit)
# 返回的记录按时间倒序，转为正序
messages = list(reversed(messages))
chat_messages: List[BaseMessage] = []
for message in messages:
chat_messages.append(HumanMessage(content=message["query"]))
chat_messages.append(AIMessage(content=message["response"]))
if not chat_messages:
return []
# prune the chat message if it exceeds the max token limit
curr_buffer_length = self.llm.get_num_tokens(get_buffer_string(chat_messages))
if curr_buffer_length > self.max_token_limit:
pruned_memory = []
while curr_buffer_length > self.max_token_limit and chat_messages:
pruned_memory.append(chat_messages.pop(0))
curr_buffer_length = self.llm.get_num_tokens(get_buffer_string(chat_messages))
return chat_messages
@property
def memory_variables(self) -> List[str]:
"""Will always return list of memory variables.
:meta private:
"""
return [self.memory_key]
def load_memory_variables(self, inputs: Dict[str, Any]) -> Dict[str, Any]:
"""Return history buffer."""
buffer: Any = self.buffer
if self.return_messages:
final_buffer: Any = buffer
else:
final_buffer = get_buffer_string(
buffer,
human_prefix=self.human_prefix,
ai_prefix=self.ai_prefix,
)
return {self.memory_key: final_buffer}
def save_context(self, inputs: Dict[str, Any], outputs: Dict[str, str]) -> None:
"""Nothing should be saved or changed"""
pass
def clear(self) -> None:
"""Nothing to clear, got a memory like a vault."""
pass |