Comments: Add wp_update_comment_counts() to reconcile stored counts

src/wp-includes/comment.php

@@ -3410,6 +3410,116 @@ function wp_update_comment_count_now( $post_id ) {
 	return true;
 }
 
+/**
+ * Recalculates the stored comment count for one or more posts.
+ *
+ * Counts are recomputed with wp_update_comment_count_now(), so they honor the
+ * {@see 'default_excluded_comment_types'} filter. Call this once after changing
+ * the excluded types, the same way flush_rewrite_rules() is called after
+ * changing rewrite rules.
+ *
+ * Each recount fires the `wp_update_comment_count` and `edit_post` hooks and is
+ * written immediately, ignoring wp_defer_comment_counting(). A full recount on a
+ * large site is slow, so run it from WP-CLI or a scheduled event rather than an
+ * activation hook. It is idempotent and safe to interrupt.
+ *
+ * Bumps the comment `last_changed` cache key when there is a post to recount.
+ * Performs no capability checks.
+ *
+ * @since 7.3.0
+ *
+ * @global wpdb $wpdb WordPress database abstraction object.
+ *
+ * @param int[]|int|null $post_ids Optional. Post ID or array of post IDs to recalculate.
+ *                                 Default null, which recalculates every post that has
+ *                                 at least one comment or a nonzero stored count.
+ * @return int Number of posts whose comment count was recalculated. Nonexistent
+ *             post IDs are skipped.
+ */
+function wp_update_comment_counts( $post_ids = null ) {
+	global $wpdb;
+
+	$recalculated = 0;
+
+	if ( null !== $post_ids ) {
+		$post_ids = array_map( 'intval', (array) $post_ids );
+		$post_ids = array_unique(
+			array_filter(
+				$post_ids,
+				static function ( $post_id ) {
+					return $post_id > 0;
+				}
+			)
+		);
+
+		if ( ! $post_ids ) {
+			return 0;
+		}
+
+		wp_cache_set_last_changed( 'comment' );
+
+		foreach ( $post_ids as $post_id ) {
+			if ( wp_update_comment_count_now( $post_id ) ) {
+				++$recalculated;
+			}
+		}
+
+		return $recalculated;
+	}
+
+	/**
+	 * Filters how many posts wp_update_comment_counts() recalculates per batch.
+	 *
+	 * @since 7.3.0
+	 *
+	 * @param int $batch_size Number of posts to look up per query. Default 1000.
+	 */
+	$batch_size = (int) apply_filters( 'wp_update_comment_counts_batch_size', 1000 );
+
+	if ( $batch_size < 1 ) {
+		$batch_size = 1;
+	}
+
+	/*
+	 * Visit posts with comment rows plus posts with a nonzero stored count, in
+	 * keyset batches. Each union arm needs its own ORDER BY and LIMIT because
+	 * MySQL does not push the outer ones into the arms. The first N rows of the
+	 * union of two ascending sets are always among the first N of each.
+	 */
+	$last_post_id = 0;
+
+	do {
+		$batch = $wpdb->get_col(
+			$wpdb->prepare(
+				"( SELECT DISTINCT comment_post_ID AS post_id FROM {$wpdb->comments} WHERE comment_post_ID > %d ORDER BY comment_post_ID LIMIT %d )
+				UNION
+				( SELECT ID AS post_id FROM {$wpdb->posts} WHERE comment_count <> 0 AND ID > %d ORDER BY ID LIMIT %d )
+				ORDER BY post_id
+				LIMIT %d",
+				$last_post_id,
+				$batch_size,
+				$last_post_id,
+				$batch_size,
+				$batch_size
+			)
+		);
+
+		if ( $batch && 0 === $last_post_id ) {
+			wp_cache_set_last_changed( 'comment' );
+		}
+
+		foreach ( $batch as $post_id ) {
+			if ( wp_update_comment_count_now( (int) $post_id ) ) {
+				++$recalculated;
+			}
+		}
+
+		$last_post_id = $batch ? (int) end( $batch ) : 0;
+	} while ( count( $batch ) === $batch_size );
+
+	return $recalculated;
+}
+
 //
 // Ping and trackback functions.
 //