includes/class-tmdo-cache-layer.php

@@ -49,7 +49,7 @@ class TMDO_Cache_Layer {
 		// Check which IDs are already cached.
 		$uncached = array();
 		foreach ( $post_ids as $pid ) {
-			$cached = wp_cache_get( "cold_{$pid}", $group );
+			$cached = wp_cache_get( TMDO_Zone_Cold::cache_key( (int) $pid, $post_type ), $group );
 			if ( false === $cached ) {
 				$uncached[] = (int) $pid;
 			}
@@ -94,7 +94,7 @@ class TMDO_Cache_Layer {
 		// Cache all results (including empty arrays for posts with no cold data).
 		foreach ( $uncached as $pid ) {
 			$data = $fetched[ $pid ] ?? array();
-			wp_cache_set( "cold_{$pid}", $data, $group, $ttl );
+			wp_cache_set( TMDO_Zone_Cold::cache_key( $pid, $post_type ), $data, $group, $ttl );
 		}
 	}
 
@@ -114,7 +114,7 @@ class TMDO_Cache_Layer {
 
 		// Force a fresh read from DB (bypasses cache).
 		$group = 'wpdo_cold_' . sanitize_key( $post_type );
-		wp_cache_delete( "cold_{$post_id}", $group );
+		wp_cache_delete( TMDO_Zone_Cold::cache_key( $post_id, $post_type ), $group );
 
 		// Re-read will populate cache.
 		TMDO_Zone_Cold::get_blob( $post_id, $post_type );
@@ -136,18 +136,18 @@ class TMDO_Cache_Layer {
 	/**
 	 * Flush all cold cache for a post type.
 	 *
-	 * Useful after bulk imports or schema changes.
+	 * Useful after bulk imports or schema changes. Bumps the post type's cache
+	 * version (new keys from now on) instead of wp_cache_flush_group(), which
+	 * Redis Object Cache runs as one server-side scan that blocks Redis on a
+	 * large group; older entries expire by their TTL.
 	 *
 	 * @param string $post_type Post type to flush.
 	 */
 	public static function flush_group( string $post_type ): void {
-		$group = 'wpdo_cold_' . sanitize_key( $post_type );
+		$versions               = get_option( TMDO_Zone_Cold::CACHE_VERSION_OPTION, array() );
-
+		$versions               = is_array( $versions ) ? $versions : array();
-		if ( function_exists( 'wp_cache_flush_group' ) ) {
+		$versions[ $post_type ] = (int) ( $versions[ $post_type ] ?? 0 ) + 1;
-			wp_cache_flush_group( $group );
+		update_option( TMDO_Zone_Cold::CACHE_VERSION_OPTION, $versions, true );
-		}
-		// If wp_cache_flush_group is not available (older WP or no object cache),
-		// individual entries will expire via TTL.
 	}
 
 	/**
@@ -183,7 +183,7 @@ class TMDO_Cache_Layer {
 		return array(
 			'groups'           => $groups,
 			'prefetch_support' => true,
-			'flush_support'    => function_exists( 'wp_cache_flush_group' ),
+			'flush_support'    => true,
 		);
 	}
 

includes/zones/class-tmdo-zone-cold.php

@@ -25,6 +25,9 @@ if ( ! defined( 'ABSPATH' ) ) {
  */
 class TMDO_Zone_Cold {
 
+	/** Option: post type → cold cache version (TMDO_Cache_Layer::flush_group()). */
+	public const CACHE_VERSION_OPTION = 'wpdo_cold_cache_version';
+
 	/**
 	 * Get the cold table name for a post type.
 	 *
@@ -45,6 +48,21 @@ class TMDO_Zone_Cold {
 		return 'wpdo_cold_' . sanitize_key( $post_type );
 	}
 
+	/**
+	 * Object-cache key of a post's cold blob. It carries the post type's cache
+	 * version once TMDO_Cache_Layer::flush_group() has bumped it (none before,
+	 * so existing entries keep their keys).
+	 *
+	 * @param int    $post_id   Post ID.
+	 * @param string $post_type Post type slug.
+	 * @return string
+	 */
+	public static function cache_key( int $post_id, string $post_type ): string {
+		$versions = get_option( self::CACHE_VERSION_OPTION, array() );
+		$version  = is_array( $versions ) ? (int) ( $versions[ $post_type ] ?? 0 ) : 0;
+		return $version ? "cold_{$post_id}_v{$version}" : "cold_{$post_id}";
+	}
+
 	/**
 	 * Ensure the cold table exists for a post type.
 	 *
@@ -92,7 +110,7 @@ class TMDO_Zone_Cold {
 	 */
 	public static function get_blob( int $post_id, string $post_type ): array {
 		$group     = self::cache_group( $post_type );
-		$cache_key = "cold_{$post_id}";
+		$cache_key = self::cache_key( $post_id, $post_type );
 
 		$cached = wp_cache_get( $cache_key, $group );
 		if ( false !== $cached ) {
@@ -202,7 +220,7 @@ class TMDO_Zone_Cold {
 		);
 		// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery,WordPress.DB.DirectDatabaseQuery.NoCaching
 
-		wp_cache_delete( "cold_{$post_id}", self::cache_group( $post_type ) );
+		wp_cache_delete( self::cache_key( $post_id, $post_type ), self::cache_group( $post_type ) );
 	}
 
 	/**
@@ -215,7 +233,7 @@ class TMDO_Zone_Cold {
 	public static function delete( int $post_id, string $post_type ): void {
 		global $wpdb;
 		$wpdb->delete( self::table( $post_type ), array( 'post_id' => $post_id ), array( '%d' ) );
-		wp_cache_delete( "cold_{$post_id}", self::cache_group( $post_type ) );
+		wp_cache_delete( self::cache_key( $post_id, $post_type ), self::cache_group( $post_type ) );
 	}
 
 	// ── Private helpers ───────────────────────────────────────────────────
@@ -264,7 +282,7 @@ class TMDO_Zone_Cold {
 		);
 
 		// Invalidate object cache.
-		wp_cache_delete( "cold_{$post_id}", self::cache_group( $post_type ) );
+		wp_cache_delete( self::cache_key( $post_id, $post_type ), self::cache_group( $post_type ) );
 	}
 
 	/**
@@ -305,6 +323,6 @@ class TMDO_Zone_Cold {
 		);
 		// phpcs:enable WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.DirectDatabaseQuery,WordPress.DB.DirectDatabaseQuery.NoCaching
 
-		wp_cache_delete( "cold_{$post_id}", self::cache_group( $post_type ) );
+		wp_cache_delete( self::cache_key( $post_id, $post_type ), self::cache_group( $post_type ) );
 	}
 }

tests/unit/CacheLayerTest.php

@@ -197,6 +197,25 @@ class CacheLayerTest extends TestCase {
 		$this->assertNotSame( [ 'stale' => true ], $GLOBALS['_wp_cache'][ $group ][ $cache_key ] ?? null );
 	}
 
+	/**
+	 * Flushing bumps the post type's cache version instead of asking the
+	 * object cache to scan the group (a server-side script on Redis that
+	 * blocks it on a large group); older entries expire by their TTL.
+	 */
+	public function test_flush_group_moves_to_new_keys_without_a_group_flush(): void {
+		$group                                   = 'wpdo_cold_hp_listing';
+		$old_key                                 = WPDO_Zone_Cold::cache_key( 1, 'hp_listing' );
+		$GLOBALS['_wp_cache'][ $group ][ $old_key ] = array( 'stale' => true );
+
+		WPDO_Cache_Layer::flush_group( 'hp_listing' );
+
+		$new_key = WPDO_Zone_Cold::cache_key( 1, 'hp_listing' );
+		$this->assertNotSame( $old_key, $new_key );
+		$this->assertFalse( wp_cache_get( $new_key, $group ) );
+		$this->assertSame( 'cold_2', WPDO_Zone_Cold::cache_key( 2, 'other_type' ), 'other post types keep their keys' );
+		$this->assertArrayHasKey( $old_key, $GLOBALS['_wp_cache'][ $group ], 'nothing scanned or deleted' );
+	}
+
 	// ── get_stats() ──────────────────────────────────────────────────────────
 
 	public function test_get_stats_includes_required_keys(): void {