rob006 As you can see in the Flarum core migration file below, the participant_count column in the discussions table belongs to Flarum core. No other extension should delete a column that belongs to Flarum.
flarum/frameworkblob/2.x/framework/core/migrations/2015_02_24_000000_create_discussions_table.php
<?php
use Flarum\Database\Migration;
use Illuminate\Database\Schema\Blueprint;
return Migration::createTable(
'discussions',
function (Blueprint $table) {
$table->increments('id');
$table->string('title', 200);
$table->integer('comments_count')->unsigned()->default(0);
$table->integer('participants_count')->unsigned()->default(0);
$table->integer('number_index')->unsigned()->default(0);
$table->dateTime('start_time');
$table->integer('start_user_id')->unsigned()->nullable();
$table->integer('start_post_id')->unsigned()->nullable();
$table->dateTime('last_time')->nullable();
$table->integer('last_user_id')->unsigned()->nullable();
$table->integer('last_post_id')->unsigned()->nullable();
$table->integer('last_post_number')->unsigned()->nullable();
}
);
