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Merge/Upsert/AddOrUpdate support
In my project I need to insert entity if it does not exist yet, or update it otherwise (somewhat like UPSERT in mongodb). As I understand in SQL it can be accomplished using MERGE, but I was not able to find MERGE in EF Core.
@NickAb I'm not sure Merge is even applicable to ORMs. Can you write a little snippet showing how you would have use it?
There isn't anything at the moment, though we could potentially do something nice (but not for 1.0.0).
@gdoron Actually, I am only interested in merge-as-upsert analog (upsert as in mongo upsert), not full-blown MERGE syntax, so it might look like:
var newFeatureForRegionSetting = new FeatureForRegionSetting();
entity.Region = region;
entity.Feature = feature;
entity.Settings = settings;
dbCtx. FeatureForRegionSettings.Upsert(x => x.region == entity.region && x.feature == entity.feature, newFeatureForRegionSetting);
which will insert newFeatureForRegionSetting if condition is not matched, or update entity if condition is matched.
I can not provide usage example for full-blown merge, as I am not that familiar with other MERGE uses.
No, I don't think so. As I understand, the issue you are referring to is about "merging disconnected graphs", so it is about interworking of EF change tracking, etc. What I am referring to is SQL MERGE statement, see docs here https://msdn.microsoft.com/en-us/library/bb510625.aspx
Ah, I've done this with a home brewed extension method but it needs to get the entity before doing the upsert. Needed to define the key value and didn't support multiple keys. Would be useful to have since it would be more performant.
There's a pattern described https://msdn.microsoft.com/en-us/data/jj592676.aspx Which is essentially what I wrapped in the extension, would be much better if the framework did this instead. Especially if it can be made to determine if the keys are default or not - without necessarily loading the entity from the data store.
Perhaps it could leverage the MERGE statement as you alluded to. Match on entity keys. I could see folks wanting the results of the MERGE returned which would complicate the operation. The simple case would be useful enough to warrant only Insert or Update with no additional complexity. Also, depends on whether or not the data store supports MERGE if its to be used to implement the feature.
There is a very handy document in PostgreSQL wiki about UPSERT in various SQL dialects. It may come handy if someone is trying to implement it in the EF.
(In practice it seems there is no agreed way how it should work, especially with unique fields, and would be a messy thing to do in EF because of it)
I know there are lots of things it would be nice to support, and limited developer time, but it's a shame this one is missing. Apart from this, my code is entirely database-independent, but it's hard to implement upsert without database support.
The usual pattern is that you try to insert, and whether it succeeds or fails, you know the relevant row is in the database. You can therefore pull it out and work with it. There are problems with this approach, though:
- As far as I can tell, you have to discard the DbContext after the insert fails, because otherwise the next SaveChanges() will retry the insert.
- EF Core seems to write an unwanted exception message into the log when the insert fails.
- Failure usually aborts transactions, so the insert attempt and the following update can't be atomic. This creates problems with races where the insert succeeds, but the row gets updated before the following update.
Just pinging this to make sure it's not totally forgotten. With the seemingly wide support of UPSERT/MERGE across databases, this could be a pretty valuable feature (although of course the specific implementations/variations would have to be investigated (see this comparative doc cited above by @Ciantic)
@roji Thanks--there's definitely a lot of value in doing this. the comparative doc is very useful--we would have to figure out what to do for SQL Server.
@ajcvickers https://docs.microsoft.com/en-us/sql/t-sql/statements/merge-transact-sql it seems to be "upsert"
I liked the idea of an Upsert command for EF Core, so I thought to make a simple extension that could be used in some of the more simple scenarios.
Considering the example above, it could be expressed like this:
dbCtx.Upsert(new FeatureForRegionSetting
{
Region = region,
Feature = feature,
Settings = settings
})
.On(x => new { x.Region, x.Feature })
.RunAsync();
But it can also handle more interesting scenarios:
DataContext.Upsert(new DailyVisits
{
UserID = userID,
Date = DateTime.UtcNow.Date,
Visits = 1,
})
.On(v => new { v.UserID, v.Date })
.UpdateColumns(v => new DailyVisits
{
Visits = v.Visits + 1,
})
.RunAsync();
I've posted the project here: https://github.com/artiomchi/FlexLabs.Upsert
I also described a bit more about it in a blog post. It's a simple extension, and can't be directly merged into EF, but I think the syntax is pretty good, and it might be useful enough for some people :)
Apparently, the update method in Entity functions as an Add or Update by default. https://docs.microsoft.com/en-us/ef/core/saving/disconnected-entities#saving-single-entities
So this might be able to be closed now?
@vovikdrg Care to define what's different? https://en.wiktionary.org/wiki/upsert defines it as a way to update or insert in databases.
@Nonary I did few comments before. Link you provided has nothing to do with technical stuff if you are asking about words definition and differences probably its wrong thread. If you really care about technical differences of upsert in sql world please check here https://docs.microsoft.com/en-us/sql/t-sql/statements/merge-transact-sql?view=sql-server-2017
@vovikdrg are you saying that EF doesn't generate the database-specific upsert command? That is important because as I said above, trying to emulate upsert with insert and update tends to lead to odd effects.
@PeteX EF will generate only update or insert commands which are different from upsert. Also what do you mean about emulate? Upsert is supported almost in all engines.At some point due to complexity maybe it make sense even to be as extension EF.Core.Extension.SqlServer, EF.Core.Extension.MySql
You don't need to emulate upsert, I was just pointing out that it doesn't work very well if you try!
@Nonary in the MS docs you linked to, it never tells you that it does an upsert:
The Update method normally marks the entity for update, not insert. However, if the entity has a auto-generated key, and no key value has been set, then the entity is instead automatically marked for insert.
So, it'll either generate an INSERT or an UPDATE sql statement, depending on the state of the entity passed to the Update() method.
@Nonary @vovikdrg @PeteX
At this point in time, there is no native Upsert functionality in Microsoft's EF Core package. If you need upsert support in EF Core, you can either manually construct the correct SQL statement for the DB engine you're using, use an SP.
Another alternative is use the FlexLabs.EntityFrameworkCore.Upsert package that I created. :smile: At the moment, it will generate the SQL statement for SQL Server, MySQL, Postgres and Sqlite, and run it immediately.
I'm continuously working on improving it, and am planning to extend it to use the EF's object state in the future, but even without that - it works quite well, and has been tested in several projects currently in production.
@PeteX any examples or arguments when it is not working? I did use it many times work like a charm. Maybe my cases were simple or I was doing something "wrong"
@vovikdrg when what didn't work sorry? I'm not sure if you're talking about EF now, EF as it was when I wrote my first comment, or emulating upsert with INSERT and UPDATE.
In general the problems are races that occur when access to data is contended, so most of the time things will work correctly.
@TanvirArjel This issue is in the Backlog milestone. This means that it is not going to happen for the 3.0 release. We will re-assess the backlog following the 3.0 release and consider this item at that time. However, keep in mind that there are many other high priority features with which it will be competing for resources.
@TanvirArjel check this https://github.com/aspnet/EntityFrameworkCore/issues/4526#issuecomment-366818031
Just a small update, tried today to implement repository InsertOrUpdate method, and it is real pain now.
Referencing the new issue that basically describes the pain you have when you need to insert or update:
https://github.com/dotnet/efcore/issues/19620
@yahorsi have you tried the library from https://github.com/dotnet/efcore/issues/4526#issuecomment-466083476?
