optimization: compare: avoid initializing config when it's not needed

This makes Schema.Equal ~25% faster in my use case

Author: Noam Preil

arrow/compare.go

@@ -40,11 +40,6 @@ func CheckMetadata() TypeEqualOption {
 // TypeEqual checks if two DataType are the same, optionally checking metadata
 // equality for STRUCT types.
 func TypeEqual(left, right DataType, opts ...TypeEqualOption) bool {
-	var cfg typeEqualsConfig
-	for _, opt := range opts {
-		opt(&cfg)
-	}
-
 	switch {
 	case left == right:
 		return true
@@ -54,6 +49,11 @@ func TypeEqual(left, right DataType, opts ...TypeEqualOption) bool {
 		return false
 	}
 
+	var cfg typeEqualsConfig
+	for _, opt := range opts {
+		opt(&cfg)
+	}
+
 	switch l := left.(type) {
 	case ExtensionType:
 		return l.ExtensionEquals(right.(ExtensionType))