[8.x] Add explain() to Query\Builder and Eloquent\Builder (#34969)

* trait

* use trait

* Update Builder.php

* Update Builder.php

Co-authored-by: Taylor Otwell <taylor@laravel.com>

src/Illuminate/Database/Concerns/ExplainsQueries.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace Illuminate\Database\Concerns;
+
+use Illuminate\Support\Collection;
+
+trait ExplainsQueries
+{
+    /**
+     * Explains the query.
+     *
+     * @return \Illuminate\Support\Collection
+     */
+    public function explain()
+    {
+        $sql = $this->toSql();
+
+        $bindings = $this->getBindings();
+
+        $explanation = $this->getConnection()->select('EXPLAIN '.$sql, $bindings);
+
+        return new Collection($explanation);
+    }
+}

src/Illuminate/Database/Eloquent/Builder.php

@@ -7,6 +7,7 @@
 use Exception;
 use Illuminate\Contracts\Support\Arrayable;
 use Illuminate\Database\Concerns\BuildsQueries;
+use Illuminate\Database\Concerns\ExplainsQueries;
 use Illuminate\Database\Eloquent\Relations\Relation;
 use Illuminate\Database\Query\Builder as QueryBuilder;
 use Illuminate\Pagination\Paginator;
@@ -23,7 +24,7 @@
  */
 class Builder
 {
-    use BuildsQueries, Concerns\QueriesRelationships, ForwardsCalls;
+    use BuildsQueries, Concerns\QueriesRelationships, ExplainsQueries, ForwardsCalls;
 
     /**
      * The base query builder instance.

src/Illuminate/Database/Query/Builder.php

@@ -6,6 +6,7 @@
 use DateTimeInterface;
 use Illuminate\Contracts\Support\Arrayable;
 use Illuminate\Database\Concerns\BuildsQueries;
+use Illuminate\Database\Concerns\ExplainsQueries;
 use Illuminate\Database\ConnectionInterface;
 use Illuminate\Database\Eloquent\Builder as EloquentBuilder;
 use Illuminate\Database\Eloquent\Relations\Relation;
@@ -23,7 +24,7 @@
 
 class Builder
 {
-    use BuildsQueries, ForwardsCalls, Macroable {
+    use BuildsQueries, ExplainsQueries, ForwardsCalls, Macroable {
         __call as macroCall;
     }