Collaboration: Replace awareness cache layer with dedicated presence table.

Introduce wp_presence table with UNIQUE KEY (room, client_id) for
atomic upserts via INSERT ... ON DUPLICATE KEY UPDATE. This eliminates
the read-modify-write race condition in the object cache approach and
removes all cache-backend branching from the awareness path.

The collaboration table becomes a clean append-only log for sync
updates only — the type column, type_client_id index, and
room_type_date index are removed.

New file: src/wp-includes/presence.php provides wp_get_presence(),
wp_set_presence(), wp_remove_presence(), wp_remove_user_presence(),
and wp_delete_expired_presence_data().

Author: josephfusco

src/wp-admin/includes/schema.php

@@ -190,16 +190,25 @@ function wp_get_db_schema( $scope = 'all', $blog_id = null ) {
 CREATE TABLE $wpdb->collaboration (
 	id bigint(20) unsigned NOT NULL auto_increment,
 	room varchar($max_index_length) NOT NULL default '',
-	type varchar(32) NOT NULL default '',
 	client_id varchar(32) NOT NULL default '',
 	user_id bigint(20) unsigned NOT NULL default '0',
 	data longtext NOT NULL,
 	date_gmt datetime NOT NULL default '0000-00-00 00:00:00',
 	PRIMARY KEY  (id),
-	KEY type_client_id (type,client_id),
 	KEY room (room,id),
-	KEY room_type_date (room,type,date_gmt),
 	KEY date_gmt (date_gmt)
+) $charset_collate;
+CREATE TABLE $wpdb->presence (
+	id bigint(20) unsigned NOT NULL auto_increment,
+	room varchar($max_index_length) NOT NULL default '',
+	client_id varchar($max_index_length) NOT NULL default '',
+	user_id bigint(20) unsigned NOT NULL default '0',
+	data text NOT NULL,
+	date_gmt datetime NOT NULL default '0000-00-00 00:00:00',
+	PRIMARY KEY  (id),
+	UNIQUE KEY room_client (room,client_id),
+	KEY date_gmt (date_gmt),
+	KEY user_id (user_id)
 ) $charset_collate;\n";
 
 	// Single site users table. The multisite flavor of the users table is handled below.

src/wp-admin/includes/upgrade.php

@@ -886,7 +886,7 @@ function upgrade_all() {
 		upgrade_682();
 	}
 
-	if ( $wp_current_db_version < 61841 ) {
+	if ( $wp_current_db_version < 61843 ) {
 		upgrade_700();
 	}
 

src/wp-includes/class-wpdb.php

@@ -300,6 +300,7 @@ class wpdb {
 		'termmeta',
 		'commentmeta',
 		'collaboration',
+		'presence',
 	);
 
 	/**
@@ -414,6 +415,15 @@ class wpdb {
 	 */
 	public $collaboration;
 
+	/**
+	 * WordPress Presence table.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @var string
+	 */
+	public $presence;
+
 	/**
 	 * WordPress Terms table.
 	 *

src/wp-includes/collaboration.php

@@ -22,7 +22,7 @@ function wp_is_collaboration_enabled() {
 	return (
 		wp_is_collaboration_allowed() &&
 		get_option( 'wp_collaboration_enabled' ) &&
-		get_option( 'db_version' ) >= 61841
+		get_option( 'db_version' ) >= 61843
 	);
 }
 
@@ -89,9 +89,8 @@ function wp_collaboration_inject_setting() {
 /**
  * Deletes stale collaboration data from the collaboration table.
  *
- * Removes non-awareness rows older than 7 days and awareness rows older
- * than 60 seconds. Rows left behind by abandoned collaborative editing
- * sessions are cleaned up to prevent unbounded table growth.
+ * Removes update rows older than 7 days. Presence data is cleaned
+ * separately via wp_delete_expired_presence_data().
  *
  * @since 7.0.0
  */
@@ -107,19 +106,14 @@ function wp_delete_old_collaboration_data() {
 		wp_clear_scheduled_hook( 'wp_delete_old_collaboration_data' );
 	}
 
-	/* Clean up rows older than 7 days. */
+	/* Clean up update rows older than 7 days. */
 	$wpdb->query(
 		$wpdb->prepare(
 			"DELETE FROM {$wpdb->collaboration} WHERE date_gmt < %s",
 			gmdate( 'Y-m-d H:i:s', time() - WEEK_IN_SECONDS )
 		)
 	);
 
-	// Clean up awareness rows older than 60 seconds.
-	$wpdb->query(
-		$wpdb->prepare(
-			"DELETE FROM {$wpdb->collaboration} WHERE type = 'awareness' AND date_gmt < %s",
-			gmdate( 'Y-m-d H:i:s', time() - 60 )
-		)
-	);
+	/* Clean up expired presence entries. */
+	wp_delete_expired_presence_data();
 }