Add castTypeCache

getCastType is called a lot when processing models with defined casts and contributes to a significant number of overall calls.  Caching the results of the key conversion can result in significant performance improvement when processing large numbers of models.

src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php

@@ -165,6 +165,13 @@ trait HasAttributes
      */
     protected static $setAttributeMutatorCache = [];
 
+    /**
+     * The cache of the converted cast types.
+     *
+     * @var array
+     */
+    protected static $castTypeCache = [];
+
     /**
      * The encrypter instance that is used to encrypt attributes.
      *
@@ -818,19 +825,23 @@ protected function getEnumCastableAttributeValue($key, $value)
      */
     protected function getCastType($key)
     {
-        if ($this->isCustomDateTimeCast($this->getCasts()[$key])) {
-            return 'custom_datetime';
-        }
+        $castType = $this->getCasts()[$key];
 
-        if ($this->isImmutableCustomDateTimeCast($this->getCasts()[$key])) {
-            return 'immutable_custom_datetime';
+        if (isset(static::$castTypeCache[$castType])) {
+            return static::$castTypeCache[$castType];
         }
 
-        if ($this->isDecimalCast($this->getCasts()[$key])) {
-            return 'decimal';
+        if ($this->isCustomDateTimeCast($castType)) {
+            $convertedCastType = 'custom_datetime';
+        } elseif ($this->isImmutableCustomDateTimeCast($castType)) {
+            $convertedCastType = 'immutable_custom_datetime';
+        } elseif ($this->isDecimalCast($castType)) {
+            $convertedCastType = 'decimal';
+        } else {
+            $convertedCastType = trim(strtolower($castType));
         }
 
-        return trim(strtolower($this->getCasts()[$key]));
+        return static::$castTypeCache[$castType] = $convertedCastType;
     }
 
     /**