[5.7] Prevent unnecessary relationship queries

src/Illuminate/Database/Eloquent/Relations/BelongsTo.php

@@ -75,6 +75,10 @@ public function __construct(Builder $query, Model $child, $foreignKey, $ownerKey
      */
     public function getResults()
     {
+        if (is_null($this->child->{$this->foreignKey})) {
+            return $this->getDefaultFor($this->parent);
+        }
+
         return $this->query->first() ?: $this->getDefaultFor($this->parent);
     }
 

src/Illuminate/Database/Eloquent/Relations/BelongsToMany.php

@@ -559,7 +559,9 @@ public function firstOrFail($columns = ['*'])
      */
     public function getResults()
     {
-        return $this->get();
+        return ! is_null($this->parent->{$this->parentKey})
+                ? $this->get()
+                : $this->related->newCollection();
     }
 
     /**

src/Illuminate/Database/Eloquent/Relations/HasMany.php

@@ -13,7 +13,9 @@ class HasMany extends HasOneOrMany
      */
     public function getResults()
     {
-        return $this->query->get();
+        return ! is_null($this->getParentKey())
+                ? $this->query->get()
+                : $this->related->newCollection();
     }
 
     /**

src/Illuminate/Database/Eloquent/Relations/HasManyThrough.php

@@ -343,7 +343,9 @@ public function findOrFail($id, $columns = ['*'])
      */
     public function getResults()
     {
-        return $this->get();
+        return ! is_null($this->farParent->{$this->localKey})
+                ? $this->get()
+                : $this->related->newCollection();
     }
 
     /**

src/Illuminate/Database/Eloquent/Relations/HasOne.php

@@ -17,6 +17,10 @@ class HasOne extends HasOneOrMany
      */
     public function getResults()
     {
+        if (is_null($this->getParentKey())) {
+            return $this->getDefaultFor($this->parent);
+        }
+
         return $this->query->first() ?: $this->getDefaultFor($this->parent);
     }
 

src/Illuminate/Database/Eloquent/Relations/MorphMany.php

@@ -13,7 +13,9 @@ class MorphMany extends MorphOneOrMany
      */
     public function getResults()
     {
-        return $this->query->get();
+        return ! is_null($this->getParentKey())
+                ? $this->query->get()
+                : $this->related->newCollection();
     }
 
     /**

src/Illuminate/Database/Eloquent/Relations/MorphOne.php

@@ -17,6 +17,10 @@ class MorphOne extends MorphOneOrMany
      */
     public function getResults()
     {
+        if (is_null($this->getParentKey())) {
+            return $this->getDefaultFor($this->parent);
+        }
+
         return $this->query->first() ?: $this->getDefaultFor($this->parent);
     }
 

src/Illuminate/Database/Eloquent/Relations/MorphTo.php

@@ -81,16 +81,6 @@ protected function buildDictionary(Collection $models)
         }
     }
 
-    /**
-     * Get the results of the relationship.
-     *
-     * @return mixed
-     */
-    public function getResults()
-    {
-        return $this->ownerKey ? parent::getResults() : null;
-    }
-
     /**
      * Get the results of the relationship.
      *