cara memperbarui nomor urut di mongodb dengan aman

Untuk melakukan ini secara atom, ketiga dokumen sampel Anda harus menjadi bagian dari dokumen yang sama. MongoDB hanya melakukan operasi secara atom pada dokumen sederhana:http://www.mongodb.org/ tampilan/DOCS/Atomic+Operations

Jika mereka adalah bagian dari satu dokumen, berikut ini akan mengubah urutan subdokumen ke-2 dan ke-3:

> db.so.find().pretty();{ "_id" :ObjectId("4f55e7ba362e2f2a734c92f8"), "subs" :[ { "author_id" :"a", "class" :"principle", "content_id" :null, "host_id" :null, "modified_date" :1330935540, "order" :1, "pub_date" :1330935540, "score" :0, "text" :"Hello World！", "vote_down_count" :0, "vote_up_count" :0 }, { "author_id" :"a", "class" :"principle", "content_id" :null, "host_id" :null, "modified_date" :1330935538, "order" :2, "pub_date" :1330935538, "score" :0, "text" :"Senang bertemu denganmu.", "vote_down_count" :0, "vote_up_count" :0 }, { "author_id" :"a", "class" :"principle", "content_id" :null, "host_id" :null, "modified_date" :1330935548, "order" :3, "pub_date" :1330935548, "skor" :0, "text" :"Bagus!", "vote_down_count" :0, "vote_up_count" :0 } ]}

Pertanyaan:

db.so.update( { _id:new ObjectId("4f55e7ba362e2f2a734c92f8")}, { $set :{ 'subs.1.order' :3, 'subs.2.order' :2 } }); 

 Hasil:
 
> db.so.find().pretty();{ "_id" :ObjectId("4f55e7ba362e2f2a734c92f8"), "subs" :[ { "author_id" :"a", "class" :"principle", "content_id" :null, "host_id" :null, "modified_date" :1330935540, "order" :1, "pub_date" :1330935540, "score" :0, "text" :"Hello World！", "vote_down_count" :0, "vote_up_count" :0 }, { "author_id" :"a", "class" :"principle", "content_id" :null, "host_id" :null, "modified_date" :1330935538, "order" :3, "pub_date" :1330935538, "score" :0, "text" :"Senang bertemu denganmu.", "vote_down_count" :0, "vote_up_count" :0 }, { "author_id" :"a", "class" :"principle", "content_id" :null, "host_id" :null, "modified_date" :1330935548, "order" :2, "pub_date" :1330935548, "score" :0, "text" :"Bagus!", "vote_down_count" :0, "vote_up_count" :0 } ]}