Fix Postgres Better Auth migration index SQL

lib/auth.ts

@@ -21,6 +21,67 @@ function parseCsvList(value: string | undefined) {
     .filter((entry) => entry.length > 0);
 }
 
+function isPostgresConnectionString(value: string | undefined) {
+  if (!value) {
+    return false;
+  }
+
+  try {
+    const protocol = new URL(value).protocol.toLowerCase();
+    return protocol === 'postgres:' || protocol === 'postgresql:';
+  } catch {
+    return /^postgres(?:ql)?:\/\//i.test(value);
+  }
+}
+
+function splitSqlStatements(sqlText: string) {
+  return sqlText
+    .split(';')
+    .map((statement) => statement.trim())
+    .filter((statement) => statement.length > 0);
+}
+
+function buildPostgresMigrationPlan(sqlText: string) {
+  const immediateStatements: string[] = [];
+  const deferredIndexStatements: string[] = [];
+  const addIndexPattern = /^alter table\s+([^\s]+)\s+add\s+index\s+([^\s]+)\s+\((.+)\)$/i;
+
+  for (const rawStatement of splitSqlStatements(sqlText)) {
+    const statement = rawStatement.replace(/\s+/g, ' ').trim();
+    const match = statement.match(addIndexPattern);
+    if (!match) {
+      immediateStatements.push(statement);
+      continue;
+    }
+
+    const [, tableName, indexName, columns] = match;
+    deferredIndexStatements.push(`create index if not exists ${indexName} on ${tableName} (${columns})`);
+  }
+
+  return [...immediateStatements, ...deferredIndexStatements];
+}
+
+async function runPostgresMigrations(pool: Pool, sqlText: string) {
+  const statements = buildPostgresMigrationPlan(sqlText);
+  if (statements.length === 0) {
+    return;
+  }
+
+  const client = await pool.connect();
+  try {
+    await client.query('BEGIN');
+    for (const statement of statements) {
+      await client.query(statement);
+    }
+    await client.query('COMMIT');
+  } catch (error) {
+    await client.query('ROLLBACK');
+    throw error;
+  } finally {
+    client.release();
+  }
+}
+
 function getPool() {
   const connectionString = process.env.DATABASE_URL?.trim();
   if (!connectionString) {
@@ -73,11 +134,18 @@ export function getAuth() {
 
 export async function ensureAuthSchema() {
   const auth = getAuth();
+  const connectionString = process.env.DATABASE_URL?.trim();
 
   if (!migrationPromise) {
     migrationPromise = (async () => {
-      const { runMigrations } = await getMigrations(auth.options);
+      const migrations = await getMigrations(auth.options);
-      await runMigrations();
+      if (isPostgresConnectionString(connectionString)) {
+        const sql = await migrations.compileMigrations();
+        await runPostgresMigrations(getPool(), sql);
+        return;
+      }
+
+      await migrations.runMigrations();
     })();
   }