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作者 Re:使用 High Replication 儲存資料 [Re:pakxpakx]
mylee





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於 2011-07-04 14:47 user profilesend a private message to userreply to postreply to postsearch all posts byselect and copy to clipboard. 
ie only, sorry for netscape users:-)add this post to my favorite list
pakxpakx wrote:
ok, 大大我明白你的意思,不過我還有一個問題
同一個entity group裡面,entities的數量有限制嗎?如果有可以透過付費擴充嗎?


Google 負責員工 (IKai L) 說沒有限制。
http://groups.google.com/group/google-appengine-java/browse_thread/thread/de7a91d92b2bc6be?pli=1

他當時提到唯一問題是你如果要一次讀出該 entity group 會遇到問題。因為當時一個 request 最多回傳 entity 數量和總大小的上限不算很大。後來是放大還是取消限制我也忘了,要再查一下才知道。


另外,ancestor query才有strongly consistency,非ancestor query,是eventual consistency,指的是非ancestor query出來的結果,有可能剛剛才put的entity還不會出現,是這個意思嗎?


要看你的 datastore 的種類,不一定都是 eventual consistency

http://code.google.com/intl/en/appengine/docs/python/datastore/queries.html

The Master/Slave Datastore and the High Replication Datastore have different guarantees when it comes to query consistency. By default:

* The Master/Slave datastore is strongly consistent for all queries.
* The High Replication datastore is strongly consistent by default for queries within an entity group. With the High Replication Datastore, non-ancestor queries are always eventually consistent.

同份文件的另一段

When you select eventual consistency for a datastore query, the indexes used by the query to gather results are also accessed with eventual consistency. Eventual consistency queries occasionally return entities that don't match the query criteria, while strong consistency queries are always transactionally consistent. (You can use transactions to ensure a consistent result set if the query uses an ancestor filter.) See Transaction Isolation in App Engine for more information on how entities and indexes are updated.


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話題樹型展開
人氣 標題 作者 字數 發文時間
1152 使用 High Replication 儲存資料 pakxpakx 210 2011-07-03 15:00
907 Re:使用 High Replication 儲存資料 mylee 604 2011-07-04 09:39
707 Re:使用 High Replication 儲存資料 pakxpakx 185 2011-07-04 09:46
889 Re:使用 High Replication 儲存資料 mylee 347 2011-07-04 10:06
715 Re:使用 High Replication 儲存資料 pakxpakx 207 2011-07-04 12:38
1189 Re:使用 High Replication 儲存資料 mylee 1628 2011-07-04 14:47
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