在数据库中获取插入实体的ID？ [英] Getting the id of an inserted entity in datomic?

问题描述

在我在数据集中运行事务以插入值后，我如何使用事务的返回值来获取创建的任何实体的ID？

After I run a transaction in datomic to insert a value, how I can use the return value of the transaction to get the ids of any entities that were created?

这里是插入后的返回值的示例：

Here is a sample of the return value I get after an insert:

#<promise$settable_future$reify__4841@7c92b2e9: {:db-before datomic.db.Db@62d0401f, :db-after datomic.db.Db@bba61dfc,
 :tx-data [#Datum{:e 13194139534331 :a 50 
:v #inst "2013-06-19T11:38:08.025-00:00" 
:tx 13194139534331 :added true} #Datum{:e 17592186045436 .....

我可以看到基础数据...如何提取它们的值？

I can see the underlying datums...how can I extract their values?

推荐答案

使用 d / resolve-tempid 。如果你要处理一个单一的实体，看看：tx-data 可以工作，但如果你的事务包含多个实体，那么你不知道它们出现在：tx-data 中。

Use d/resolve-tempid. If you were to transact a single entity, looking at :tx-data would work but if your transaction contained more than one entity, then you wouldn't know the order in which they appear in :tx-data.

您应该做的是使用（d / tempid）向您的实体提供临时ID >或其字面表示＃db / id [：db.part / user _negativeId _] ，然后使用 d / resolve-tempid 从您的临时ID转到数据库给出的真实ID。代码看起来像：

What you should do is give temporary ids to your entities (before transacting them) using either (d/tempid) or its literal representation #db/id[:db.part/user _negativeId_] and then use d/resolve-tempid to go from your temporary id to the real id given by the database. The code would look something like:

(d/resolve-tempid (d/db conn) (:tempids tx) (d/tempid :db.part/user _negativeId_))

strong>，请参阅此 gist 。

For a full code sample, see this gist.

这篇关于在数据库中获取插入实体的ID？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！