From 5975c2d2faf9230ec505f6214c9481fb659d55ed Mon Sep 17 00:00:00 2001
From: David Herrera <david@alley.com>
Date: Thu, 7 Nov 2024 23:28:24 -0500
Subject: [PATCH] Cache items fetched during the request in memory

---
 CHANGELOG.md                |  8 ++++++-
 src/class-big-pit.php       | 27 ++++++++++++++++++++++
 tests/Unit/CrudUnitTest.php | 45 +++++++++++++++++++++++++++++++++++++
 3 files changed, 79 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index aadef05..ffa3d87 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,9 +2,15 @@
 
 This library adheres to [Semantic Versioning](https://semver.org/) and [Keep a CHANGELOG](https://keepachangelog.com/en/1.0.0/).
 
+## 0.4.0
+
+### Added
+
+- In-memory cache of items fetched during the request.
+
 ## 0.3.0
 
-## Changed
+### Changed
 
 - When storing items with the PSR-16 adapter, the group name is now automatically prefixed to avoid unintended data loss when flushing the cache.
 
diff --git a/src/class-big-pit.php b/src/class-big-pit.php
index 506bb37..355eea1 100644
--- a/src/class-big-pit.php
+++ b/src/class-big-pit.php
@@ -30,6 +30,15 @@ final class Big_Pit implements Feature {
 	 */
 	private bool $ready = false;
 
+	/**
+	 * Cached values.
+	 *
+	 * @phpstan-var array<string, array<string, mixed>>
+	 *
+	 * @var array[]
+	 */
+	private array $cache = [];
+
 	/**
 	 * Instance.
 	 *
@@ -79,6 +88,16 @@ public function get( string $key, string $group ): mixed {
 			return null;
 		}
 
+		if ( isset( $this->cache[ $group ] ) && array_key_exists( $key, $this->cache[ $group ] ) ) {
+			$value = $this->cache[ $group ][ $key ];
+
+			if ( is_object( $value ) ) {
+				$value = clone $value;
+			}
+
+			return $value;
+		}
+
 		$value = $wpdb->get_var(
 			$wpdb->prepare(
 				"SELECT item_value FROM {$wpdb->big_pit} WHERE item_group = %s AND item_key = %s LIMIT 1",
@@ -91,6 +110,8 @@ public function get( string $key, string $group ): mixed {
 			$value = maybe_unserialize( $value );
 		}
 
+		$this->cache[ $group ][ $key ] = $value;
+
 		return $value;
 	}
 
@@ -141,6 +162,8 @@ public function set( string $key, mixed $value, string $group ): void {
 				[ '%s', '%s', '%s' ],
 			);
 		}
+
+		unset( $this->cache[ $group ][ $key ] );
 	}
 
 	/**
@@ -164,6 +187,8 @@ public function delete( string $key, string $group ): void {
 			],
 			[ '%s', '%s' ],
 		);
+
+		unset( $this->cache[ $group ][ $key ] );
 	}
 
 	/**
@@ -185,6 +210,8 @@ public function flush_group( string $group ): void {
 			],
 			[ '%s' ],
 		);
+
+		unset( $this->cache[ $group ] );
 	}
 
 	/**
diff --git a/tests/Unit/CrudUnitTest.php b/tests/Unit/CrudUnitTest.php
index 6f94450..53ae46a 100644
--- a/tests/Unit/CrudUnitTest.php
+++ b/tests/Unit/CrudUnitTest.php
@@ -68,4 +68,49 @@ public function test_crud() {
 		// key3 should still be there.
 		$this->assertSame( $val3, $big_pit->get( $key3, $grp2 ) );
 	}
+
+	/**
+	 * Test for expected number of queries with the in-memory cache.
+	 */
+	public function test_in_memory_cache() {
+		global $wpdb;
+
+		$big_pit = Big_Pit::instance();
+
+		// Two fetches of the same key should only result in one query.
+		$num_queries_before = $wpdb->num_queries;
+		$big_pit->get( 'key1', 'group1' );
+		$big_pit->get( 'key1', 'group1' );
+		$this->assertSame( 1, $wpdb->num_queries - $num_queries_before );
+
+		$big_pit->set( 'key1', 'value1', 'group1' );
+
+		// Value has changed, so there should be another query.
+		$num_queries_before = $wpdb->num_queries;
+		$big_pit->get( 'key1', 'group1' );
+		$this->assertSame( 1, $wpdb->num_queries - $num_queries_before );
+
+		// Fetching it again should not result in another query.
+		$big_pit->get( 'key1', 'group1' );
+		$this->assertSame( 1, $wpdb->num_queries - $num_queries_before );
+
+		$big_pit->delete( 'key1', 'group1' );
+
+		// Value has changed, so there should be another query.
+		$num_queries_before = $wpdb->num_queries;
+		$big_pit->get( 'key1', 'group1' );
+		$this->assertSame( 1, $wpdb->num_queries - $num_queries_before );
+
+		$big_pit->set( 'key1', 'value1', 'group1' );
+		$big_pit->set( 'key2', 'value2', 'group1' );
+		$big_pit->get( 'key1', 'group1' );
+		$big_pit->get( 'key2', 'group1' );
+		$big_pit->flush_group( 'group1' );
+
+		// All values have changed, so there should be queries for each value in the group that was set.
+		$num_queries_before = $wpdb->num_queries;
+		$big_pit->get( 'key1', 'group1' );
+		$big_pit->get( 'key2', 'group1' );
+		$this->assertSame( 2, $wpdb->num_queries - $num_queries_before );
+	}
 }