View file vendor/illuminate/database/Query/Processors/PostgresProcessor.php

<?php

namespace Illuminate\Database\Query\Processors;

use Illuminate\Database\Query\Builder;

class PostgresProcessor extends Processor
{
    /**
     * Process an "insert get ID" query.
     *
     * @param  \Illuminate\Database\Query\Builder  $query
     * @param  string  $sql
     * @param  array  $values
     * @param  string|null  $sequence
     * @return int
     */
    public function processInsertGetId(Builder $query, $sql, $values, $sequence = null)
    {
        $connection = $query->getConnection();

        $connection->recordsHaveBeenModified();

        $result = $connection->selectFromWriteConnection($sql, $values)[0];

        $sequence = $sequence ?: 'id';

        $id = is_object($result) ? $result->{$sequence} : $result[$sequence];

        return is_numeric($id) ? (int) $id : $id;
    }

    /**
     * Process the results of a column listing query.
     *
     * @param  array  $results
     * @return array
     */
    public function processColumnListing($results)
    {
        return array_map(function ($result) {
            return ((object) $result)->column_name;
        }, $results);
    }
}