Remove customer analytics data upon order deletion (https://github.com/woocommerce/woocommerce-admin/pull/5171)

This deletes the associated customer record when an order is deleted, provided that this is the only order for the customer.

plugins/woocommerce-admin/src/API/Reports/Customers/DataStore.php

@@ -85,6 +85,7 @@ class DataStore extends ReportsDataStore implements DataStoreInterface {
 	public static function init() {
 		add_action( 'edit_user_profile_update', array( __CLASS__, 'update_registered_customer' ) );
 		add_action( 'updated_user_meta', array( __CLASS__, 'update_registered_customer_via_last_active' ), 10, 3 );
+		add_action( 'woocommerce_analytics_delete_order_stats', array( __CLASS__, 'sync_on_order_delete' ), 15, 2 );
 	}
 
 	/**
@@ -101,6 +102,30 @@ class DataStore extends ReportsDataStore implements DataStoreInterface {
 		}
 	}
 
+	/**
+	 * Sync customers data after an order was deleted.
+	 *
+	 * When an order is deleted, the customer record is deleted from the
+	 * table if the customer has no other orders.
+	 *
+	 * @param int $order_id Order ID.
+	 * @param int $customer_id Customer ID.
+	 */
+	public static function sync_on_order_delete( $order_id, $customer_id ) {
+		$customer_id = absint( $customer_id );
+
+		if ( 0 === $customer_id ) {
+			return;
+		}
+
+		// Calculate the amount of orders remaining for this customer.
+		$order_count = self::get_order_count( $customer_id );
+
+		if ( 0 === $order_count ) {
+			self::delete_customer( $customer_id );
+		}
+	}
+
 	/**
 	 * Maps ordering specified by the user to columns in the database/fields in the data.
 	 *
@@ -572,6 +597,34 @@ class DataStore extends ReportsDataStore implements DataStoreInterface {
 		);
 	}
 
+	/**
+	 * Retrieve the amount of orders made by a customer.
+	 *
+	 * @param int $customer_id Customer ID.
+	 * @return int|null Amount of orders for customer or null on failure.
+	 */
+	public static function get_order_count( $customer_id ) {
+		global $wpdb;
+		$customer_id = absint( $customer_id );
+
+		if ( 0 === $customer_id ) {
+			return null;
+		}
+
+		$result = $wpdb->get_var(
+			$wpdb->prepare(
+				"SELECT COUNT( order_id ) FROM {$wpdb->prefix}wc_order_stats WHERE customer_id = %d",
+				$customer_id
+			)
+		);
+
+		if ( is_null( $result ) ) {
+			return null;
+		}
+
+		return (int) $result;
+	}
+
 	/**
 	 * Update the database with customer data.
 	 *

plugins/woocommerce-admin/src/API/Reports/Orders/Stats/DataStore.php

@@ -12,6 +12,7 @@ use \Automattic\WooCommerce\Admin\API\Reports\DataStoreInterface;
 use \Automattic\WooCommerce\Admin\API\Reports\TimeInterval;
 use \Automattic\WooCommerce\Admin\API\Reports\SqlQuery;
 use \Automattic\WooCommerce\Admin\API\Reports\Cache as ReportsCache;
+use \Automattic\WooCommerce\Admin\API\Reports\Customers\DataStore as CustomersDataStore;
 
 /**
  * API\Reports\Orders\Stats\DataStore.
@@ -576,13 +577,19 @@ class DataStore extends ReportsDataStore implements DataStoreInterface {
 			return;
 		}
 
+		// Retrieve customer details before the order is deleted.
+		$order       = wc_get_order( $order_id );
+		$customer_id = absint( CustomersDataStore::get_existing_customer_id_from_order( $order ) );
+
+		// Delete the order.
 		$wpdb->delete( self::get_db_table_name(), array( 'order_id' => $order_id ) );
 		/**
 		 * Fires when orders stats are deleted.
 		 *
 		 * @param int $order_id Order ID.
+		 * @param int $customer_id Customer ID.
 		 */
-		do_action( 'woocommerce_analytics_delete_order_stats', $order_id );
+		do_action( 'woocommerce_analytics_delete_order_stats', $order_id, $customer_id );
 
 		ReportsCache::invalidate();
 	}

plugins/woocommerce-admin/tests/reports/class-wc-tests-reports-customers.php

@@ -0,0 +1,118 @@
+<?php
+/**
+ * Reports customers tests.
+ *
+ * @package WooCommerce\Admin\Tests\Customers
+ */
+
+use \Automattic\WooCommerce\Admin\API\Reports\Customers\Stats\DataStore;
+
+/**
+ * Class WC_Tests_Reports_Customers
+ */
+class WC_Tests_Reports_Customer extends WC_Unit_Test_Case {
+
+	/**
+	 * Test order count caluclation for customer.
+	 *
+	 * @covers \Automattic\WooCommerce\Admin\API\Reports\Customers\DataStore::get_order_count
+	 */
+	public function test_customer_order_count() {
+		WC_Helper_Reports::reset_stats_dbs();
+
+		// Create a customer.
+		$customer = WC_Helper_Customer::create_customer();
+
+		// Create product.
+		$product = new WC_Product_Simple();
+		$product->set_name( 'Test Product' );
+		$product->set_regular_price( 25 );
+		$product->save();
+
+		WC_Helper_Queue::run_all_pending();
+
+		$customer_id = DataStore::get_customer_id_by_user_id( $customer->get_id() ); // This is the customer ID from lookup table.
+
+		// Create 3 orders.
+		foreach ( range( 1, 3 ) as $i ) {
+			$order = WC_Helper_Order::create_order( $customer->get_id(), $product );
+			$order->save();
+		}
+
+		WC_Helper_Queue::run_all_pending();
+
+		// Customer should have 3 orders.
+		$this->assertSame( 3, DataStore::get_order_count( $customer_id ) );
+
+		// Failure from bad customer IDs.
+		$this->assertSame( null, DataStore::get_order_count( 0 ) );
+		$this->assertSame( null, DataStore::get_order_count( 'ABC' ) );
+		$this->assertSame( null, DataStore::get_order_count( false ) );
+		$this->assertSame( null, DataStore::get_order_count( null ) );
+	}
+
+	/**
+	 * Test customer lookup tables are cleaned after deleting an order.
+	 *
+	 * A customer record should only be deleted if the customer has no other orders.
+	 *
+	 * @covers \Automattic\WooCommerce\Admin\API\Reports\Customers\DataStore::sync_on_order_delete
+	 */
+	public function test_order_deletion_removes_customer() {
+		WC_Helper_Reports::reset_stats_dbs();
+
+		// Create a customer.
+		$customer = WC_Helper_Customer::create_customer();
+
+		// Create products.
+		$product1 = new WC_Product_Simple();
+		$product1->set_name( 'Test Product 1' );
+		$product1->set_regular_price( 1 );
+		$product1->save();
+
+		$product2 = new WC_Product_Simple();
+		$product2->set_name( 'Test Product 2' );
+		$product2->set_regular_price( 2 );
+		$product2->save();
+
+		WC_Helper_Queue::run_all_pending();
+
+		// Create the first order.
+		$order1 = WC_Helper_Order::create_order( $customer->get_id(), $product1 );
+		$order1->save();
+
+		// Create the second order.
+		$order2 = WC_Helper_Order::create_order( $customer->get_id(), $product2 );
+		$order2->save();
+
+		WC_Helper_Queue::run_all_pending();
+
+		$customer_id = DataStore::get_customer_id_by_user_id( $customer->get_id() ); // This is the customer ID from lookup table.
+
+		// Customer should remain in lookup table after first order deleted.
+		$order1->delete( true );
+		$this->assertCount( 1, $this->get_customer_record( $customer_id ), 'customer remains' );
+
+		// Customer should be removed in lookup table after both orders are deleted.
+		$order2->delete( true );
+		$this->assertCount( 0, $this->get_customer_record( $customer_id ), 'customer removed' );
+	}
+
+	/**
+	 * Get a customer's record from the database.
+	 *
+	 * @param int $customer_id Analytics Customer ID (not WP User ID).
+	 */
+	private function get_customer_record( $customer_id ) {
+		global $wpdb;
+
+		$results = $wpdb->get_results(
+			$wpdb->prepare(
+				"SELECT * FROM {$wpdb->prefix}wc_customer_lookup WHERE customer_id = %d",
+				$customer_id
+			)
+		);
+
+		return $results;
+	}
+}