Laravel BelongsToMany in different connections

BelongsToManyInDifferentConnections.php

<?php

namespace App\Models;

use Illuminate\Database\ConnectionInterface;
use Illuminate\Database\Eloquent\Builder;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsToMany;

class BelongsToManyInDifferentConnections extends BelongsToMany
{
    public $connection;

    public function __construct(
        Builder $query,
        Model $parent,
        ConnectionInterface $connection,
        $table,
        $foreignKey,
        $relatedKey,
        $relationName = null
    ) {
        $this->connection = $connection;

        parent::__construct( $query, $parent, $table, $foreignKey, $relatedKey, $foreignKey, $relatedKey, $relationName );
    }

    /**
     * Set the where clause for the relation query.
     *
     * @return $this
     */
    protected function addWhereConstraints()
    {
        return $this;
    }

    protected function performJoin( $query = null )
    {
        $query = $query ?: $this->query;

        $baseTable = $this->related->getTable();

        $key = $baseTable . '.' . $this->related->getKeyName();

        $idsQuery = $this->parent->getConnection()
            ->table( $this->table )
            ->distinct()
            ->select( $this->relatedKey );

        if (!is_null( $this->parent->id )) {
            $idsQuery->where( $this->parent->getForeignKey(), $this->parent->id );
        }

        $ids = $idsQuery->pluck( $this->relatedKey )->all();

        $query->whereIn( $key, $ids );

        return $query;
    }

    protected function aliasedPivotColumns()
    {
        $defaults = [ $this->foreignPivotKey, $this->relatedPivotKey ];

        return collect( array_merge( $defaults, $this->pivotColumns ) )
            ->map( function ( $column ) {
                if (!in_array( $column, [ 'created_at', 'updated_at' ] )) {
                    return $column;
                }

                return $this->related->getTable() . '.' . $column . ' as pivot_' . $column;
            } )
            ->map( function ( $column ) {
                if (!in_array( $column, [ $this->relatedKey ] )) {
                    return $column;
                }

                return $this->related->getTable() . '.' . $this->related->getKeyName() . ' as pivot_' . $column;
            } )
            ->map( function ( $column ) {
                if ($column !== $this->parent->getForeignKey()) {
                    return $column;
                }

                return $this->parent->getConnection()->raw( $this->parent->id . ' as pivot_' . $column );
            } )
            ->unique()
            ->all();
    }

    /**
     * Get a new plain query builder for the pivot table.
     *
     * @return \Illuminate\Database\Query\Builder
     */
    public function newPivotStatement()
    {
        return $this->connection->table( $this->table );
    }
}

HasBelongsToManyInDifferentConnections.php

<?php

namespace App\Models;

use Illuminate\Database\ConnectionInterface;

trait HasBelongsToManyInDifferentConnections
{
    /**
     * Define a many-to-many relationship.
     *
     * @param  string              $related
     * @param  ConnectionInterface $connection
     * @param  string              $table
     * @param  string              $foreignKey
     * @param  string              $relatedKey
     * @param  string              $relation
     *
     * @return BelongsToManyInDifferentConnections
     */
    public function belongsToManyInDifferentConnections(
        $related,
        $table = null,
        ConnectionInterface $connection = null,
        $foreignKey = null,
        $relatedKey = null,
        $relation = null
    ) {
        if (is_null( $relation )) {
            $relation = $this->guessBelongsToManyRelation();
        }

        $instance = $this->newRelatedInstance( $related );

        $foreignKey = $foreignKey ?: $this->getForeignKey();

        $relatedKey = $relatedKey ?: $instance->getForeignKey();

        if (is_null( $table )) {
            $table = $this->joiningTable( $related );
        }

        if (is_null( $connection )) {
            $connection = $this->getConnection();
        }

        return new BelongsToManyInDifferentConnections(
            $instance->newQuery(), $this, $connection, $table, $foreignKey, $relatedKey, $relation
        );
    }
}

Hello Rodrigo, thanks for this gist!!

It is working and saving records in pivot, but when I add withPivot() sql can't find the extra pivot columns because is looking for them in the second connection database.

I have this:

    public function businessCenters()
    {
        return $this->belongsToManyInDifferentConnections(BusinessCenter::class, 'account_business_center')
        ->withPivot('income', 'expense');
    }

Any idea why?