From d4f3720040d5c8da211ab0b9de1012ea7fdd3690 Mon Sep 17 00:00:00 2001
From: Buzz <buzz@buywhere.ai>
Date: Sat, 18 Jul 2026 06:39:26 +0000
Subject: [PATCH] fix(BUY-63030): route MCP catalog reads through catalogDb;
 surface unavailable on zero-count category fallback

- Switch search_products, get_product, compare_products, get_deals,
  list_categories, find_best_price, probeDiscountPctColumn, and the
  regional FTS fallback in get_deals from primary db to catalogDb so
  the canonical ~127M catalog is served.
- Keep ingestion/auth/health endpoints on primary db (write paths +
  liveness checks).
- list_categories already recomputes unavailable from cached rows so
  pre-fix zero-count static fallbacks now surface unavailable:true
  after deploy.
---
 mcp-railway/src/routes/mcp.ts | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/mcp-railway/src/routes/mcp.ts b/mcp-railway/src/routes/mcp.ts
index 41db1cf7d..d542f2e65 100644
--- a/mcp-railway/src/routes/mcp.ts
+++ b/mcp-railway/src/routes/mcp.ts
@@ -1,5 +1,5 @@
 import { Router, Request, Response, NextFunction } from 'express';
-import { db, redis, vectorDb } from '../config';
+import { db, redis, vectorDb, catalogDb } from '../config';
 import { embedQuery } from '../jobs/embedProducts';
 import { requireApiKey, checkRateLimit } from '../middleware/apiKey';
 import { queryLogMiddleware } from '../middleware/queryLog';
@@ -13,9 +13,9 @@ async function acquireMcpClient() {
   let timer: NodeJS.Timeout | undefined;
   try {
     return await Promise.race([
-      db.connect(),
+      catalogDb.connect(),
       new Promise<never>((_, reject) => {
-        timer = setTimeout(() => reject(new Error('mcp_db_pool_acquire_timeout')), MCP_DB_ACQUIRE_TIMEOUT_MS);
+        timer = setTimeout(() => reject(new Error('mcp_catalog_db_pool_acquire_timeout')), MCP_DB_ACQUIRE_TIMEOUT_MS);
       }),
     ]);
   } finally {
@@ -193,7 +193,7 @@ let _hasDiscountPct: boolean | undefined;
 
 async function probeDiscountPctColumn(): Promise<boolean> {
   try {
-    const probe = await db.query(
+    const probe = await catalogDb.query(
       `SELECT is_generated FROM information_schema.columns WHERE table_name = 'products' AND column_name = 'discount_pct' LIMIT 1`
     );
     return probe.rows.length > 0 && probe.rows[0].is_generated === 'ALWAYS';
@@ -280,9 +280,9 @@ async function handleSearchProducts(args: Record<string, unknown>) {
   // blocking the entire 12s statement_timeout. The DB itself is fast (70-130ms) so
   // any 8-12s MCP latency is pool-acquisition contention, not query execution.
   const searchClient = await Promise.race([
-    db.connect(),
+    catalogDb.connect(),
     new Promise<never>((_, reject) =>
-      setTimeout(() => reject(new Error('db.connect timeout after 2000ms')), 2000)
+      setTimeout(() => reject(new Error('catalog_db.connect timeout after 2000ms')), 2000)
     ),
   ]).catch(() => {
     throw { code: -32603, message: 'Database connection timeout' };
@@ -469,7 +469,7 @@ async function handleGetProduct(args: Record<string, unknown>) {
 
   let result;
   try {
-    result = await db.query(
+    result = await catalogDb.query(
       `SELECT id, sku AS source, source AS domain, url, title,
               price, currency, image_url, brand, category_path,
               avg_rating AS rating, review_count, metadata, updated_at, region, country_code
@@ -503,7 +503,7 @@ async function handleCompareProducts(args: Record<string, unknown>) {
   const placeholders = validIds.map((_, i) => `$${i + 1}`).join(',');
   let result;
   try {
-    result = await db.query(
+    result = await catalogDb.query(
       `SELECT id, sku AS source, source AS domain, url, title,
               price, currency, image_url, brand, category_path,
               avg_rating AS rating, review_count, metadata, updated_at, region, country_code
@@ -525,7 +525,7 @@ async function getRegionalProductSample(
   t0: number,
 ) {
   try {
-    const result = await db.query(
+    const result = await catalogDb.query(
       `SELECT id, sku AS source, source AS domain, url, title,
               price, NULL::numeric AS original_price, currency, image_url,
               metadata, updated_at, region, country_code, 0::numeric AS discount_pct
@@ -940,6 +940,11 @@ async function handleFindBestPrice(args: Record<string, unknown>) {
   };
 }
 
+// BUY-63030: catalog reads (search_products, get_product, compare_products,
+// get_deals, list_categories, find_best_price, probeDiscountPctColumn) now
+// route through catalogDb so we serve the canonical ~127M catalog instead of
+// the primary maglev DB. Ingestion/auth/health stays on primary db.
+
 // BUY-31929: MCP tool to ingest products — delegates to the same logic as
 // POST /v1/ingest/products but via JSON-RPC tool call.
 async function handleIngestProducts(args: Record<string, unknown>) {
@@ -1252,7 +1257,7 @@ async function handleFindSimilar(args: Record<string, unknown>) {
   // Step 3: fetch product details from main DB
   const nearIds = nearResult.rows.map(r => r.product_id);
   const ph = nearIds.map((_, i) => `$${i + 1}`).join(',');
-  const detailResult = await db.query(
+  const detailResult = await catalogDb.query(
     `SELECT id, title, price, currency, source AS domain, url, image_url
      FROM products WHERE id IN (${ph}) AND is_active = true`,
     nearIds