From 4f51f1efb5ff809931cd5fac7e37be43ffdf526c Mon Sep 17 00:00:00 2001
From: Daniel <daniel@danvics.com>
Date: Tue, 14 Apr 2026 03:55:09 +0200
Subject: [PATCH] Pin critical auth indexes to COLLATE "C" (ICU-drift immune)
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idx_users_email and idx_sessions_token_hash now use byte-order
collation so a future ICU library bump cannot silently corrupt the
indexes the way it did this week. The columns themselves retain
their default collation; only the index comparison is C, which is
safe for these because:

  - users.email is lowercased ASCII in practice
  - user_sessions.token_hash is SHA-256 hex (pure ASCII)

Both are used for equality lookups only, never ORDER BY. Migration
is idempotent, gated on app_settings.migration.text_indexes_c.

Slug indexes on learning_* tables left at default for now — those
are also ASCII in practice but under lighter load; the startup
drift check + auto-REINDEX covers them.
---
 src/db/database.js | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/src/db/database.js b/src/db/database.js
index b17ac18..30849f1 100644
--- a/src/db/database.js
+++ b/src/db/database.js
@@ -50,6 +50,37 @@ async function initDatabase() {
       console.warn('⚠️  Collation check skipped:', e.message);
     }
 
+    // Convert lookup-only text indexes to COLLATE "C" so a future ICU/glibc
+    // version bump cannot silently corrupt them. Idempotent — driven by a
+    // flag in app_settings so we only do the DROP/CREATE once.
+    try {
+      var done = await client.query(
+        "SELECT value FROM app_settings WHERE key = 'migration.text_indexes_c'"
+      ).catch(function() { return { rows: [] }; });
+      if (!done.rows.length || done.rows[0].value !== 'true') {
+        console.log('Migrating text lookup indexes to COLLATE "C"...');
+        var indexMigrations = [
+          // users.email — primary auth lookup
+          'DROP INDEX IF EXISTS idx_users_email',
+          'CREATE INDEX idx_users_email ON users (email COLLATE "C")',
+          // user_sessions.token_hash — session auth
+          'DROP INDEX IF EXISTS idx_sessions_token_hash',
+          'CREATE INDEX idx_sessions_token_hash ON user_sessions (token_hash COLLATE "C")'
+        ];
+        for (var i = 0; i < indexMigrations.length; i++) {
+          await client.query(indexMigrations[i]);
+        }
+        // Mark complete — create the setting row if the table exists.
+        await client.query(
+          "INSERT INTO app_settings (key, value) VALUES ('migration.text_indexes_c', 'true') " +
+          "ON CONFLICT (key) DO UPDATE SET value = 'true'"
+        ).catch(function() {});
+        console.log('✅ Text indexes: migrated to COLLATE "C" (ICU-drift immune)');
+      }
+    } catch (e) {
+      console.warn('⚠️  Index migration skipped:', e.message);
+    }
+
     await client.query(`
       CREATE TABLE IF NOT EXISTS users (
         id SERIAL PRIMARY KEY,