Query::buildJoin

protected function buildJoin()
{
	// collapse v2.0 single value joins into one
	if ($this->entity instanceof ElementV2Entity)
	{
		// table alias for all the records (cut b_ prefix)
		$propSTable = $this->entity->getSingleValueTableName();
		$commonAlias = mb_substr($propSTable, 2);

		// found first join and changed alias. all other joins to be removed
		$changed = false;

		// table aliases to be changed in chains
		$replacedAliases = [];

		// 1. collapse joins
		foreach ($this->join_map as $k => $join)
		{
			// check join
			if ($join['table'] === $propSTable && $join['type'] === Join::TYPE_INNER)
			{
				/** @var ConditionTree[]|string[] $join */
				$conditions = $join['reference']->getConditions();

				// check on condition
				if (count($conditions) === 1 && $conditions[0]->getColumn() === 'ID' && $conditions[0]->getOperator() === '=')
				{
					// collect table aliases to rewrite in chains
					$replacedAliases[$join['alias']] = true;

					if (!$changed)
					{
						// make the only one change
						$this->join_map[$k]['alias'] = $commonAlias;

						$changed = true;
					}
					else
					{
						// remove from registry
						unset($this->join_map[$k]);
					}

				}
			}
		}

		// 2. rewrite aliases
		foreach ($this->global_chains as $chain)
		{
			if (!empty($replacedAliases[$chain->getLastElement()->getParameter('talias')]))
			{
				$chain->getLastElement()->setParameter('talias', $commonAlias);
			}
		}
	}

	return parent::buildJoin();
}