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| """ | |
| backend/app/pipeline/nodes/rewrite_query.py | |
| CRAG (Corrective RAG) query rewriter — fires exactly once per request when: | |
| 1. The first retrieval attempt returned no chunks above the relevance threshold. | |
| 2. The query contains at least one meaningful non-stop-word token. | |
| Calls Gemini Flash (temp 0.7) to produce one alternative phrasing that preserves | |
| the visitor's intent but uses different vocabulary. The pipeline then runs Retrieve | |
| and Rerank a second time with this new query. There is exactly one retry — the | |
| graph routing enforces this via the retrieval_attempts counter in state. | |
| """ | |
| from __future__ import annotations | |
| import logging | |
| from typing import Any | |
| from app.models.pipeline import PipelineState | |
| from app.services.gemini_client import GeminiClient | |
| logger = logging.getLogger(__name__) | |
| _REWRITE_PROMPT = """\ | |
| A search query failed to find relevant results in a portfolio knowledge base about Darshan Chheda. | |
| The knowledge base contains his blog posts, project descriptions, CV/resume, and GitHub README files. | |
| Original query: {query} | |
| Rephrase this query using different vocabulary that might better match how the content is written. | |
| Strategies: expand abbreviations, use synonyms, reframe as "did Darshan..." if the query uses a name/tech. | |
| Output ONLY the rewritten query — one sentence, no explanation, no quotes. | |
| """ | |
| # Same stop-word set as generate.py — keeps modules consistent. | |
| _STOP_WORDS = frozenset({ | |
| "a", "an", "the", "is", "are", "was", "were", "be", "been", "being", | |
| "have", "has", "had", "do", "does", "did", "will", "would", "could", | |
| "should", "may", "might", "can", "to", "of", "in", "on", "for", | |
| "with", "at", "by", "from", "and", "or", "but", "not", "what", | |
| "who", "how", "why", "when", "where", "tell", "me", "about", "his", | |
| "he", "him", "any", "some", "that", "this", "it", "its", | |
| }) | |
| def _has_meaningful_token(query: str) -> bool: | |
| """True when the query has at least one non-stop-word token of length >= 3.""" | |
| return any( | |
| w not in _STOP_WORDS and len(w) >= 3 | |
| for w in __import__("re").findall(r"[a-z]+", query.lower()) | |
| ) | |
| def make_rewrite_query_node(gemini_client: GeminiClient) -> Any: | |
| async def rewrite_query_node(state: PipelineState) -> dict: | |
| query = state["query"] | |
| logger.info("CRAG: rewriting failed query %r", query) | |
| if not gemini_client.is_configured: | |
| # No Gemini — pass query through unchanged; second retrieve will also fail | |
| # and generate will handle the not-found path gracefully. | |
| logger.debug("Gemini not configured; skipping query rewrite.") | |
| return { | |
| "rewritten_query": query, | |
| "retrieval_attempts": state.get("retrieval_attempts", 1) + 1, | |
| "query_embedding": None, # Force re-embed so retrieve doesn't use stale embedding | |
| } | |
| try: | |
| response = await gemini_client._client.aio.models.generate_content( | |
| model=gemini_client._model, | |
| contents=_REWRITE_PROMPT.format(query=query), | |
| config={"temperature": 0.7}, | |
| ) | |
| rewritten = (response.text or query).strip().strip('"').strip("'") | |
| except Exception as exc: | |
| logger.warning("Query rewrite Gemini call failed (%s); using original.", exc) | |
| rewritten = query | |
| if not rewritten or rewritten == query: | |
| logger.debug("Rewrite produced no change; using original query.") | |
| rewritten = query | |
| else: | |
| logger.info("CRAG rewrite: %r → %r", query, rewritten) | |
| # Clearing query_embedding forces the retrieve node to re-embed the new query. | |
| # retrieval_attempts is incremented so the graph does not loop again after | |
| # this second retrieval attempt. | |
| return { | |
| "query": rewritten, | |
| "rewritten_query": rewritten, | |
| "retrieval_attempts": state.get("retrieval_attempts", 1) + 1, | |
| "query_embedding": None, | |
| } | |
| return rewrite_query_node | |