refactor: migrate from qdrant to postgres+pgvector

manifests/deployment.yaml

@@ -23,8 +23,8 @@ spec:
             - containerPort: 8000
               name: http
           env:
-            - name: QDRANT_URL
-              value: "http://qdrant.knowledge-mcp.svc:6333"
+            - name: DATABASE_URL
+              value: "postgresql://postgres:password@postgres.knowledge-mcp.svc:5432/knowledge"
             - name: TEI_URL
               value: "http://text-embeddings.tei.svc.cluster.local:8080"
           resources:

manifests/postgres.yaml

@@ -0,0 +1,66 @@
+apiVersion: apps/v1
+kind: StatefulSet
+metadata:
+  name: postgres
+  namespace: knowledge-mcp
+  labels:
+    app: postgres
+spec:
+  serviceName: postgres
+  replicas: 1
+  selector:
+    matchLabels:
+      app: postgres
+  template:
+    metadata:
+      labels:
+        app: postgres
+    spec:
+      containers:
+        - name: postgres
+          image: ankane/pgvector:v0.5.1
+          ports:
+            - containerPort: 5432
+              name: postgres
+          env:
+            - name: POSTGRES_USER
+              value: "postgres"
+            - name: POSTGRES_PASSWORD
+              value: "password"
+            - name: POSTGRES_DB
+              value: "knowledge"
+            - name: PGDATA
+              value: "/var/lib/postgresql/data/pgdata"
+          volumeMounts:
+            - name: storage
+              mountPath: /var/lib/postgresql/data
+          resources:
+            requests:
+              cpu: "100m"
+              memory: "256Mi"
+            limits:
+              cpu: "500m"
+              memory: "512Mi"
+  volumeClaimTemplates:
+    - metadata:
+        name: storage
+      spec:
+        accessModes: [ "ReadWriteOnce" ]
+        resources:
+          requests:
+            storage: 5Gi
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: postgres
+  namespace: knowledge-mcp
+  labels:
+    app: postgres
+spec:
+  ports:
+    - port: 5432
+      targetPort: 5432
+      name: postgres
+  selector:
+    app: postgres

manifests/qdrant.yaml

@@ -1,65 +0,0 @@
-apiVersion: apps/v1
-kind: StatefulSet
-metadata:
-  name: qdrant
-  namespace: knowledge-mcp
-  labels:
-    app: qdrant
-spec:
-  serviceName: qdrant
-  replicas: 1
-  selector:
-    matchLabels:
-      app: qdrant
-  template:
-    metadata:
-      labels:
-        app: qdrant
-    spec:
-      containers:
-        - name: qdrant
-          image: qdrant/qdrant:v1.13.0
-          ports:
-            - containerPort: 6333
-              name: http
-            - containerPort: 6334
-              name: grpc
-          env:
-            - name: QDRANT__STORAGE__STORAGE_PATH
-              value: /qdrant/storage
-          volumeMounts:
-            - name: storage
-              mountPath: /qdrant/storage
-          resources:
-            requests:
-              cpu: "200m"
-              memory: "512Mi"
-            limits:
-              cpu: "1000m"
-              memory: "1Gi"
-  volumeClaimTemplates:
-    - metadata:
-        name: storage
-      spec:
-        accessModes: [ "ReadWriteOnce" ]
-        resources:
-          requests:
-            storage: 10Gi
----
-apiVersion: v1
-kind: Service
-metadata:
-  name: qdrant
-  namespace: knowledge-mcp
-  labels:
-    app: qdrant
-spec:
-  ports:
-    - port: 6333
-      targetPort: 6333
-      name: http
-    - port: 6334
-      targetPort: 6334
-      name: grpc
-  selector:
-    app: qdrant

requirements.txt

@@ -1,6 +1,7 @@
 mcp
 httpx
-qdrant-client
+psycopg[binary]
+pgvector
 beautifulsoup4
 pypdf
 python-dotenv

server.py

@@ -1,21 +1,75 @@
 import os
 import httpx
 from mcp.server.fastmcp import FastMCP
-from qdrant_client import QdrantClient
-from qdrant_client.models import Distance, VectorParams, PointStruct
+import psycopg
+from pgvector.psycopg import register_vector
 import uuid
 import logging
-import io
+import json
 from pypdf import PdfReader
+from contextlib import contextmanager
 
 # Configuration
-QDRANT_URL = os.getenv("QDRANT_URL", "http://qdrant.openshift-gitops.svc:6333")
+DATABASE_URL = os.getenv("DATABASE_URL", "postgresql://postgres:password@postgres.knowledge-mcp.svc:5432/knowledge")
 TEI_URL = os.getenv("TEI_URL", "http://text-embeddings.tei.svc.cluster.local:8080")
 EMBEDDING_DIM = 768  # BAAI/bge-base-en-v1.5
 
 # Initialize
 mcp = FastMCP("knowledge-mcp")
-qdrant = QdrantClient(url=QDRANT_URL)
+
+@contextmanager
+def get_db():
+    """Provide a database connection."""
+    conn = psycopg.connect(DATABASE_URL, autocommit=True)
+    # Register vector type handler
+    register_vector(conn)
+    try:
+        yield conn
+    finally:
+        conn.close()
+
+def init_db():
+    """Initialize database schema."""
+    try:
+        with get_db() as conn:
+            conn.execute("CREATE EXTENSION IF NOT EXISTS vector")
+            
+            # Notebooks table (simple registry)
+            conn.execute("""
+                CREATE TABLE IF NOT EXISTS notebooks (
+                    name TEXT PRIMARY KEY,
+                    created_at TIMESTAMP DEFAULT NOW()
+                )
+            """)
+            
+            # Chunks table
+            conn.execute(f"""
+                CREATE TABLE IF NOT EXISTS chunks (
+                    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+                    notebook TEXT REFERENCES notebooks(name) ON DELETE CASCADE,
+                    content TEXT NOT NULL,
+                    embedding VECTOR({EMBEDDING_DIM}),
+                    source TEXT,
+                    metadata JSONB,
+                    created_at TIMESTAMP DEFAULT NOW()
+                )
+            """)
+            
+            # Index for fast search
+            conn.execute("""
+                CREATE INDEX IF NOT EXISTS chunks_embedding_idx ON chunks 
+                USING hnsw (embedding vector_cosine_ops)
+            """)
+            logging.info("Database initialized successfully.")
+    except Exception as e:
+        logging.error(f"Database initialization failed: {e}")
+
+# Run init on import (or startup)
+# In a real app, this might be a separate migration step, but for MCP self-contained:
+try:
+    init_db()
+except Exception as e:
+    logging.warning(f"Could not initialize DB immediately (might be waiting for connection): {e}")
 
 def get_embedding(text: str) -> list[float]:
     """Get embedding from TEI."""
@@ -43,18 +97,20 @@ def chunk_text(text: str, chunk_size: int = 500, overlap: int = 50) -> list[str]
 
 @mcp.tool()
 def create_notebook(name: str) -> str:
-    """Create a new RAG notebook (Qdrant collection)."""
+    """Create a new RAG notebook."""
     clean_name = name.lower().replace(" ", "-")
     
-    # Check if exists
-    if qdrant.collection_exists(clean_name):
-        return f"Notebook '{clean_name}' already exists."
-
-    qdrant.create_collection(
-        collection_name=clean_name,
-        vectors_config=VectorParams(size=EMBEDDING_DIM, distance=Distance.COSINE),
-    )
-    return f"Notebook '{clean_name}' created successfully."
+    try:
+        with get_db() as conn:
+            # Check existence
+            res = conn.execute("SELECT 1 FROM notebooks WHERE name = %s", (clean_name,)).fetchone()
+            if res:
+                return f"Notebook '{clean_name}' already exists."
+            
+            conn.execute("INSERT INTO notebooks (name) VALUES (%s)", (clean_name,))
+            return f"Notebook '{clean_name}' created successfully."
+    except Exception as e:
+        return f"Error creating notebook: {e}"
 
 @mcp.tool()
 def add_source(notebook: str, content: str, source_name: str, format: str = "text") -> str:
@@ -62,8 +118,14 @@ def add_source(notebook: str, content: str, source_name: str, format: str = "tex
     Add content to a notebook.
     format: 'text' or 'pdf_path' (local path inside container)
     """
-    if not qdrant.collection_exists(notebook):
-        return f"Error: Notebook '{notebook}' does not exist."
+    clean_name = notebook.lower().replace(" ", "-")
+    
+    try:
+        with get_db() as conn:
+            if not conn.execute("SELECT 1 FROM notebooks WHERE name = %s", (clean_name,)).fetchone():
+                return f"Error: Notebook '{clean_name}' does not exist."
+    except Exception as e:
+        return f"Database error: {e}"
 
     text_to_process = ""
     
@@ -78,52 +140,63 @@ def add_source(notebook: str, content: str, source_name: str, format: str = "tex
         text_to_process = content
 
     chunks = chunk_text(text_to_process)
-    points = []
+    count = 0
 
-    for i, chunk in enumerate(chunks):
-        try:
-            vector = get_embedding(chunk)
-            points.append(PointStruct(
-                id=str(uuid.uuid4()),
-                vector=vector,
-                payload={
-                    "source": source_name,
-                    "text": chunk,
-                    "chunk_index": i,
-                    "total_chunks": len(chunks)
-                }
-            ))
-        except Exception as e:
-            logging.error(f"Failed to embed chunk {i}: {e}")
-            continue
-
-    if points:
-        qdrant.upsert(collection_name=notebook, points=points)
-        return f"Added {len(points)} chunks from '{source_name}' to '{notebook}'."
-    return "No content added (empty or failed)."
+    try:
+        with get_db() as conn:
+            for i, chunk in enumerate(chunks):
+                try:
+                    vector = get_embedding(chunk)
+                    meta = {
+                        "chunk_index": i,
+                        "total_chunks": len(chunks)
+                    }
+                    
+                    conn.execute("""
+                        INSERT INTO chunks (notebook, content, embedding, source, metadata)
+                        VALUES (%s, %s, %s, %s, %s)
+                    """, (clean_name, chunk, vector, source_name, json.dumps(meta)))
+                    count += 1
+                except Exception as e:
+                    logging.error(f"Failed to process chunk {i}: {e}")
+                    continue
+            return f"Added {count} chunks from '{source_name}' to '{clean_name}'."
+            
+    except Exception as e:
+        return f"Failed to add source: {e}"
 
 @mcp.tool()
 def query_notebook(notebook: str, query: str, limit: int = 5) -> str:
     """Query the notebook for relevant context."""
-    if not qdrant.collection_exists(notebook):
-        return f"Error: Notebook '{notebook}' does not exist."
-
+    clean_name = notebook.lower().replace(" ", "-")
+    
     try:
         vector = get_embedding(query)
-        hits = qdrant.search(
-            collection_name=notebook,
-            query_vector=vector,
-            limit=limit
-        )
+        
+        with get_db() as conn:
+            # Check notebook
+            if not conn.execute("SELECT 1 FROM notebooks WHERE name = %s", (clean_name,)).fetchone():
+                return f"Error: Notebook '{clean_name}' does not exist."
 
-        results = []
-        for hit in hits:
-            score = hit.score
-            text = hit.payload.get('text', '').replace('\n', ' ')
-            source = hit.payload.get('source', 'unknown')
-            results.append(f"[{score:.2f}] {source}: {text}...")
+            # Cosine distance (<=>) sort ASC (closest first)
+            results = conn.execute("""
+                SELECT content, source, (1 - (embedding <=> %s::vector)) as score
+                FROM chunks
+                WHERE notebook = %s
+                ORDER BY embedding <=> %s::vector ASC
+                LIMIT %s
+            """, (vector, clean_name, vector, limit)).fetchall()
+            
+            output = []
+            for row in results:
+                content, source, score = row
+                output.append(f"[{score:.2f}] {source}: {content.replace(chr(10), ' ')}...")
+            
+            if not output:
+                return "No relevant matches found."
+                
+            return "\n".join(output)
 
-        return "\n".join(results)
     except Exception as e:
         return f"Query failed: {e}"