Upsert Add To Set Or Update if Exist

[Kader Belbina]

I am using the C# driver and intend to have on document for graphs
that looks like this:

{
id: someid
name: "somename"
datapoints: {
{ 06/20/10: Date, somecounter: somevalue }
{ 06/21/10: Date, somecounter: somevalue }
{ 06/22/10: Date, somecounter: somevalue }
}
}

I am trying to figure out either using the C# driver how to :
- increment somecounter if the array entry exists or
- add to set (create) the array entry if it does exist

I am attempting to use an upsert and only have one trip to the db.

Any advice? Hope this isn't too confusing.

[Scott Hernandez]

It is best to create the datapoints ahead of time, and then just increment the counters when needed. That way you can decouple the two operations. Is that possible for you?

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[Kader Belbina]

The problem is I am trying to upsert the entire document it is not
guaranteed that a document with "somename" will exist and there can be
a very large number of new documents every day.

Here's what I've got

var query = Query.EQ("Name", nameWeAreLookingFor);

var update = Update.Set("age", age);

// need to add the graph data to the update

collection.Update(query, update, UpdateFlags.Upsert);

[Scott Hernandez]

I think you will need a feature that doesn't exist yet for your current structure (https://jira.mongodb.org/browse/SERVER-340). If you post the structure of your document (and a sample), and what you are trying to do we may be able to help you adjust to something which will work.

[Kader Belbina]

I posted the sample and what I am trying to do here.

You mean post something in more detail on the forum or post something
in more detail on the link provided?

[Scott Hernandez]

I meant something here with more detail about the updates. What does this "// need to add the graph data to the update" mean in practice?

The sample you posted was generic and didn't seem specific to what you are really doing; it seem contrived.

What is the process for incrementing counters?

[Kader Belbina]

Okay well its for a database that tracks poker hands. A document might
look something like this:

{
"Name": "Screenname",
"Site": 1,
"TotalHands": 4548,
"WinningsGraphData" :
{
{ Date: "06/20/11", Winnings: 864.32 },
{ Date: "06/21/11", Winnings: 554.32 },
{ Date: "06/22/11", Winnings: -332.45 },
{ Date: "06/28/11", Winnings: 164.32 }
}

So when I insert a new hand history I also need to update the graphs
data for that player. They may have never played a hand on that date
so it would be a new entry, or they may have so I need to increment
the winnings. In addition, when I update the graphs for that hand the
player may not even exist so the entire player is upserted.

[Scott Hernandez]

Unfortunately I can't see a good way to do this (in a single update w/upsert) without something like $iset or without support for $set + $inc in the same array element; both of which are coming....

I would suggest that for now you do two updates, and make them dependent. You can do the first ($inc based on name + date), check the result and then do the second (if the $inc doesn't hit an existing doc).

[Kader Belbina]

So when you say check the result you mean do a query.

1 - upsert non array fields
2 - Query to see if the date exists in the array.
3 - Upsert or add to set depending on step 2.

So this would be 3 database operations?

Thanks for the help,
I take it there are plans to implement a feature to make this possible
in 1 action. Any ETA?

[Robert Stam]

I would do it this way:

1. Attempt to increment an existing Winnings entry
2. If that fails, attempt to add a new Winnings entry to an existing
user
3. If that fails, add a new user

This would be 1 database operation when adding new winnings for the
same day, 2 database operations when adding new winnings for a new day
to an existing user, and 3 database operations for a new user. That
means most of the time it would be 1 or 2 operations.

Here's a sample program I wrote to test that this really works:

http://www.pastie.org/1917357

You could cut this down to just 1 or 2 database operations if your
data model were slightly different:

{
Name : "Robert",
Site : 1,
TotalHands : 1234,
WinningsGraphData : {
Date20110517 : 100.00,
Date20110518 : 200.00
}
}

where we are using the dates as part of the names of the winnings
entries.

On May 17, 12:40 am, Kader Belbina <ka...@nitricburnstudios.com>
wrote:

[Kader Belbina]

Awesome. Thanks for the help and the code sample.