Ayende @ Rahien

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Better patching API for RavenDB: Creating New Documents

A while ago we introduced the ability to send js scripts to RavenDB for server side execution. And we have just recently completed a nice improvement on that feature, the ability to create new documents from existing ones.

Here is how it works:

store.DatabaseCommands.UpdateByIndex("TestIndex",
                                     new IndexQuery {Query = "Exported:false"},
                                     new ScriptedPatchRequest { Script = script }
  ).WaitForCompletion();

Where the script looks like this:

for(var i = 0; i < this.Comments.length; i++ ) {
   PutDocument('comments/', {
    Title: this.Comments[i].Title,
    User: this.Comments[i].User.Name,
    By: this.Comments[i].User.Id
  });
}

this.Export = true;

This will create a set of documents for each of the embedded documents.

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Posted By: Ayende Rahien

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Comments

Daniel Lang
05/10/2013 09:53 AM by
Daniel Lang

This helps a great deal with schema migrations. Btw, what happens when we patch lots of documents this way, create new documents along the way and then there is an error and execution stops... is then entire patch operation transactional, or is there any way to make it transactional?

Daniel Marbach
05/10/2013 12:02 PM by
Daniel Marbach

Daniel, Patching API is not transactional.

tobi
05/10/2013 12:34 PM by
tobi

It all converges to SQL...

Ayende Rahien
05/11/2013 06:24 AM by
Ayende Rahien

Daniel, Patching is transactional on a single document, yes. That is, if you create a 1000 documents in a patch, and it fails on the 1001 document, it will all go away.

However, it is not transactional over set operations. We pulse the transaction along the way at various points to avoid high memory usage, and that means that stuff that happened for a document in the beginning of the operation will be there if the operation fails for a much later document.

Since documents are independent, and a single document patch operation is transactional, we don't see this as a problem

Ayende Rahien
05/11/2013 06:24 AM by
Ayende Rahien

Tobi, Actually, not really.

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