create user_id index on visits table

server/migrations/20241223155527_visits_user_id_index.js

@@ -0,0 +1,32 @@
+const env = require("../env");
+
+const isMySQL = env.DB_CLIENT === "mysql" || env.DB_CLIENT === "mysql2";
+
+/**
+ * @param { import("knex").Knex } knex
+ * @returns { Promise<void> }
+ */
+async function up(knex) {
+  // IF NOT EXISTS is not available on MySQL So if you're
+  // using MySQL you should make sure you don't have these indexes already 
+  const ifNotExists = isMySQL ? "" : "IF NOT EXISTS";
+
+  await knex.raw(`
+    CREATE INDEX ${ifNotExists} visits_user_id_index ON visits (user_id);
+  `);
+};
+
+/**
+ * @param { import("knex").Knex } knex
+ * @returns { Promise<void> }
+ */
+async function down(knex) {
+  await knex.raw(`
+    DROP INDEX visits_user_id_index;
+  `);
+};
+
+module.exports = {
+  up, 
+  down,
+}