From fdf930714738ef3799011231b6576d585a06f7c4 Mon Sep 17 00:00:00 2001
From: Zen0space <tartnenas_kai@outlook.com>
Date: Wed, 8 Apr 2026 11:56:31 +0800
Subject: [PATCH] fix(db): use partialFilterExpression for stripeCustomerId
 unique index

The original migration used { sparse: true, unique: true } which still
fails with E11000 when multiple users have stripeCustomerId: null
(sparse only skips missing fields, not explicit nulls).

- Fix 000001 in place: replace sparse with partialFilterExpression
  so only real string Stripe IDs are included in the unique index
- Add 000004 safety net: drops and recreates the index properly
  for environments where 000001 partially applied
---
 .../20260407000001_add_stripe_fields.js       | 11 +++--
 ...0407000004_fix_stripe_customer_id_index.js | 48 +++++++++++++++++++
 2 files changed, 56 insertions(+), 3 deletions(-)
 create mode 100644 packages/kal-db/migrations/20260407000004_fix_stripe_customer_id_index.js

diff --git a/packages/kal-db/migrations/20260407000001_add_stripe_fields.js b/packages/kal-db/migrations/20260407000001_add_stripe_fields.js
index 8deb3cf..490b1f2 100644
--- a/packages/kal-db/migrations/20260407000001_add_stripe_fields.js
+++ b/packages/kal-db/migrations/20260407000001_add_stripe_fields.js
@@ -19,9 +19,14 @@ export const up = async (db, client) => {
   );
 
   // Create index on stripeCustomerId for webhook lookups
-  await db
-    .collection("users")
-    .createIndex({ stripeCustomerId: 1 }, { sparse: true, unique: true });
+  // Use partialFilterExpression so null values are excluded from uniqueness
+  await db.collection("users").createIndex(
+    { stripeCustomerId: 1 },
+    {
+      unique: true,
+      partialFilterExpression: { stripeCustomerId: { $type: "string" } },
+    }
+  );
 };
 
 export const down = async (db, client) => {
diff --git a/packages/kal-db/migrations/20260407000004_fix_stripe_customer_id_index.js b/packages/kal-db/migrations/20260407000004_fix_stripe_customer_id_index.js
new file mode 100644
index 0000000..16414b7
--- /dev/null
+++ b/packages/kal-db/migrations/20260407000004_fix_stripe_customer_id_index.js
@@ -0,0 +1,48 @@
+/**
+ * Migration: Fix stripeCustomerId index using partialFilterExpression
+ *
+ * Safety net for environments where migration 000001 partially applied —
+ * the updateMany set stripeCustomerId: null on all users, but the
+ * createIndex with { sparse: true, unique: true } failed because sparse
+ * indexes still include documents where the field is explicitly null.
+ *
+ * This drops any existing stripeCustomerId index and recreates it with
+ * a partialFilterExpression that only indexes documents where
+ * stripeCustomerId is a string — completely excluding null/missing values
+ * from the uniqueness constraint.
+ */
+
+export const up = async (db, client) => {
+  // Drop the existing index if it exists (may be sparse or broken)
+  await db
+    .collection("users")
+    .dropIndex("stripeCustomerId_1")
+    .catch(() => {});
+
+  // Recreate with partialFilterExpression — only enforce uniqueness on real Stripe IDs
+  await db.collection("users").createIndex(
+    { stripeCustomerId: 1 },
+    {
+      unique: true,
+      partialFilterExpression: { stripeCustomerId: { $type: "string" } },
+    }
+  );
+
+  console.log(
+    "✅ Recreated stripeCustomerId index with partialFilterExpression (string only)"
+  );
+};
+
+export const down = async (db, client) => {
+  // Revert to the sparse unique index from the original migration
+  await db
+    .collection("users")
+    .dropIndex("stripeCustomerId_1")
+    .catch(() => {});
+
+  await db
+    .collection("users")
+    .createIndex({ stripeCustomerId: 1 }, { sparse: true, unique: true });
+
+  console.log("✅ Reverted stripeCustomerId index to sparse unique");
+};