Feed in docs till we reach a token limit (#401)

backend/danswer/configs/app_configs.py

@@ -138,7 +138,12 @@
 #####
 NUM_RETURNED_HITS = 50
 NUM_RERANKED_RESULTS = 15
-NUM_GENERATIVE_AI_INPUT_DOCS = 5
+# We feed in document chunks until we reach this token limit.
+# Default is ~5 full chunks (max chunk size is 2000 chars), although some chunks
+# may be smaller which could result in passing in more total chunks
+NUM_DOCUMENT_TOKENS_FED_TO_GENERATIVE_MODEL = int(
+    os.environ.get("NUM_DOCUMENT_TOKENS_FED_TO_GENERATIVE_MODEL") or (512 * 5)
+)
 # 1 edit per 2 characters, currently unused due to fuzzy match being too slow
 QUOTE_ALLOWED_ERROR_PERCENT = 0.05
 QA_TIMEOUT = int(os.environ.get("QA_TIMEOUT") or "10")  # 10 seconds

backend/danswer/direct_qa/answer_question.py

@@ -2,7 +2,7 @@
 
 from danswer.chunking.models import InferenceChunk
 from danswer.configs.app_configs import DISABLE_GENERATIVE_AI
-from danswer.configs.app_configs import NUM_GENERATIVE_AI_INPUT_DOCS
+from danswer.configs.app_configs import NUM_DOCUMENT_TOKENS_FED_TO_GENERATIVE_MODEL
 from danswer.configs.app_configs import QA_TIMEOUT
 from danswer.configs.constants import IGNORE_FOR_QA
 from danswer.datastores.document_index import get_default_document_index
@@ -11,6 +11,7 @@
 from danswer.direct_qa.exceptions import OpenAIKeyMissing
 from danswer.direct_qa.exceptions import UnknownModelError
 from danswer.direct_qa.llm_utils import get_default_qa_model
+from danswer.direct_qa.qa_utils import get_usable_chunks
 from danswer.search.danswer_helper import query_intent
 from danswer.search.keyword_search import retrieve_keyword_documents
 from danswer.search.models import QueryFlow
@@ -107,18 +108,19 @@ def answer_qa_query(
         chunk for chunk in ranked_chunks if chunk.metadata.get(IGNORE_FOR_QA)
     ]
 
-    chunk_offset = offset_count * NUM_GENERATIVE_AI_INPUT_DOCS
-    if chunk_offset >= len(filtered_ranked_chunks):
-        raise ValueError("Chunks offset too large, should not retry this many times")
+    # get all chunks that fit into the token limit
+    usable_chunks = get_usable_chunks(
+        chunks=filtered_ranked_chunks,
+        token_limit=NUM_DOCUMENT_TOKENS_FED_TO_GENERATIVE_MODEL,
+        offset=offset_count,
+    )
+    logger.debug(
+        f"Chunks fed to LLM: {[chunk.semantic_identifier for chunk in usable_chunks]}"
+    )
 
     error_msg = None
     try:
-        answer, quotes = qa_model.answer_question(
-            query,
-            filtered_ranked_chunks[
-                chunk_offset : chunk_offset + NUM_GENERATIVE_AI_INPUT_DOCS
-            ],
-        )
+        answer, quotes = qa_model.answer_question(query, usable_chunks)
     except Exception as e:
         # exception is logged in the answer_question method, no need to re-log
         answer, quotes = None, None

backend/danswer/direct_qa/qa_utils.py

@@ -10,6 +10,7 @@
 import regex
 
 from danswer.chunking.models import InferenceChunk
+from danswer.configs.app_configs import NUM_DOCUMENT_TOKENS_FED_TO_GENERATIVE_MODEL
 from danswer.configs.app_configs import QUOTE_ALLOWED_ERROR_PERCENT
 from danswer.configs.constants import GEN_AI_API_KEY_STORAGE_KEY
 from danswer.configs.model_configs import GEN_AI_API_KEY
@@ -21,6 +22,7 @@
 from danswer.direct_qa.qa_prompts import QUOTE_PAT
 from danswer.direct_qa.qa_prompts import UNCERTAINTY_PAT
 from danswer.dynamic_configs import get_dynamic_config_store
+from danswer.llm.utils import check_number_of_tokens
 from danswer.utils.logger import setup_logger
 from danswer.utils.text_processing import clean_model_quote
 from danswer.utils.text_processing import shared_precompare_cleanup
@@ -254,3 +256,48 @@ def simulate_streaming_response(model_out: str) -> Generator[str, None, None]:
     """Mock streaming by generating the passed in model output, character by character"""
     for token in model_out:
         yield token
+
+
+def _get_usable_chunks(
+    chunks: list[InferenceChunk], token_limit: int
+) -> list[InferenceChunk]:
+    total_token_count = 0
+    usable_chunks = []
+    for chunk in chunks:
+        chunk_token_count = check_number_of_tokens(chunk.content)
+        if total_token_count + chunk_token_count > token_limit:
+            break
+
+        total_token_count += chunk_token_count
+        usable_chunks.append(chunk)
+
+    # try and return at least one chunk if possible. This chunk will
+    # get truncated later on in the pipeline. This would only occur if
+    # the first chunk is larger than the token limit (usually due to character
+    # count -> token count mismatches caused by special characters / non-ascii
+    # languages)
+    if not usable_chunks and chunks:
+        usable_chunks = [chunks[0]]
+
+    return usable_chunks
+
+
+def get_usable_chunks(
+    chunks: list[InferenceChunk],
+    token_limit: int = NUM_DOCUMENT_TOKENS_FED_TO_GENERATIVE_MODEL,
+    offset: int = 0,
+) -> list[InferenceChunk]:
+    offset_into_chunks = 0
+    usable_chunks: list[InferenceChunk] = []
+    for _ in range(min(offset + 1, 1)):  # go through this process at least once
+        if offset_into_chunks >= len(chunks) and offset_into_chunks > 0:
+            raise ValueError(
+                "Chunks offset too large, should not retry this many times"
+            )
+
+        usable_chunks = _get_usable_chunks(
+            chunks=chunks[offset_into_chunks:], token_limit=token_limit
+        )
+        offset_into_chunks += len(usable_chunks)
+
+    return usable_chunks

backend/danswer/llm/utils.py

@@ -1,5 +1,7 @@
+from collections.abc import Callable
 from collections.abc import Iterator
 
+import tiktoken
 from langchain.prompts.base import StringPromptValue
 from langchain.prompts.chat import ChatPromptValue
 from langchain.schema import PromptValue
@@ -69,3 +71,17 @@ def convert_input(lm_input: LanguageModelInput) -> str:
 
 def should_be_verbose() -> bool:
     return LOG_LEVEL == "debug"
+
+
+def check_number_of_tokens(
+    text: str, encode_fn: Callable[[str], list] | None = None
+) -> int:
+    """Get's the number of tokens in the provided text, using the provided encoding
+    function. If none is provided, default to the tiktoken encoder used by GPT-3.5
+    and GPT-4.
+    """
+
+    if encode_fn is None:
+        encode_fn = tiktoken.get_encoding("cl100k_base").encode
+
+    return len(encode_fn(text))

backend/danswer/server/search_backend.py

@@ -9,7 +9,7 @@
 from danswer.auth.users import current_user
 from danswer.chunking.models import InferenceChunk
 from danswer.configs.app_configs import DISABLE_GENERATIVE_AI
-from danswer.configs.app_configs import NUM_GENERATIVE_AI_INPUT_DOCS
+from danswer.configs.app_configs import NUM_DOCUMENT_TOKENS_FED_TO_GENERATIVE_MODEL
 from danswer.configs.constants import IGNORE_FOR_QA
 from danswer.datastores.document_index import get_default_document_index
 from danswer.db.engine import get_session
@@ -22,6 +22,7 @@
 from danswer.direct_qa.exceptions import UnknownModelError
 from danswer.direct_qa.interfaces import DanswerAnswerPiece
 from danswer.direct_qa.llm_utils import get_default_qa_model
+from danswer.direct_qa.qa_utils import get_usable_chunks
 from danswer.search.danswer_helper import query_intent
 from danswer.search.danswer_helper import recommend_search_flow
 from danswer.search.keyword_search import retrieve_keyword_documents
@@ -247,17 +248,19 @@ def stream_qa_portions(
             chunk for chunk in ranked_chunks if not chunk.metadata.get(IGNORE_FOR_QA)
         ]
 
-        chunk_offset = offset_count * NUM_GENERATIVE_AI_INPUT_DOCS
-        if chunk_offset >= len(filtered_ranked_chunks):
-            raise ValueError(
-                "Chunks offset too large, should not retry this many times"
-            )
+        # get all chunks that fit into the token limit
+        usable_chunks = get_usable_chunks(
+            chunks=filtered_ranked_chunks,
+            token_limit=NUM_DOCUMENT_TOKENS_FED_TO_GENERATIVE_MODEL,
+            offset=offset_count,
+        )
+        logger.debug(
+            f"Chunks fed to LLM: {[chunk.semantic_identifier for chunk in usable_chunks]}"
+        )
+
         try:
             for response_packet in qa_model.answer_question_stream(
-                query,
-                filtered_ranked_chunks[
-                    chunk_offset : chunk_offset + NUM_GENERATIVE_AI_INPUT_DOCS
-                ],
+                query, usable_chunks
             ):
                 if response_packet is None:
                     continue

deployment/docker_compose/docker-compose.dev.legacy.yml

@@ -64,6 +64,7 @@ services:
       - GEN_AI_API_KEY=${GEN_AI_API_KEY:-}
       - GEN_AI_ENDPOINT=${GEN_AI_ENDPOINT:-}
       - GEN_AI_HOST_TYPE=${GEN_AI_HOST_TYPE:-}
+      - NUM_DOCUMENT_TOKENS_FED_TO_GENERATIVE_MODEL=${NUM_DOCUMENT_TOKENS_FED_TO_GENERATIVE_MODEL:-}
       - POSTGRES_HOST=relational_db
       - QDRANT_HOST=vector_db
       - TYPESENSE_HOST=search_engine

deployment/docker_compose/docker-compose.dev.yml

@@ -21,6 +21,7 @@ services:
       - GEN_AI_API_KEY=${GEN_AI_API_KEY:-}
       - GEN_AI_ENDPOINT=${GEN_AI_ENDPOINT:-}
       - GEN_AI_HOST_TYPE=${GEN_AI_HOST_TYPE:-}
+      - NUM_DOCUMENT_TOKENS_FED_TO_GENERATIVE_MODEL=${NUM_DOCUMENT_TOKENS_FED_TO_GENERATIVE_MODEL:-}
       - POSTGRES_HOST=relational_db
       - VESPA_HOST=index
       - LOG_LEVEL=${LOG_LEVEL:-info}