@Scout what does this error mean

Invariant failed. Description: Tried to retrieve asset key from an assets definition with multiple asset keys

The error message you're encountering indicates that there is an attempt to retrieve a single asset key from an

AssetsDefinition

that contains multiple asset keys. In Dagster, an

AssetsDefinition

can represent one or more assets, and each asset is associated with an

AssetKey

. When you have an

AssetsDefinition

that defines multiple assets, trying to access a single asset key as if the definition only contained one asset will result in this error. This is because the system expects a clear indication of which specific asset key you are trying to access when there are multiple possibilities. To resolve this error, you should ensure that you are referencing the correct asset key explicitly when dealing with an

AssetsDefinition

that includes multiple asset keys. If you need to retrieve a specific asset key, you should use the appropriate method or property that allows you to specify which asset key you are interested in. If you need further assistance with this issue, please provide more context or code snippets, and I can help guide you on how to address the problem based on the documentation.

@Scout How does this work when i am using

multi_asset

I am trying to load multi_asset via factory and add it to definition

When using

multi_asset

in Dagster, you are defining a single op or graph that produces multiple assets at once. Each asset produced by a

multi_asset

is represented by an output, and you must specify these outputs using the

outs

parameter of the

@multi_asset

decorator. Here's a basic example from the documentation on how to define a multi-asset:

python from dagster import AssetOut, multi_asset  @multi_asset(     outs={         "my_string_asset": AssetOut(),         "my_int_asset": AssetOut(),     } ) def my_function():     return "abc", 123

In this example,

my_function

is a multi-asset that produces two assets,

my_string_asset

and

my_int_asset

. If you are trying to load a

multi_asset

via a factory and add it to a definition, you would typically create a factory function that returns a list of

multi_asset

definitions. Each

multi_asset

definition can then be added to your repository definition. Here's a simplified example based on the documentation:

python from dagster import multi_asset, AssetOut  def my_asset_factory():     # Define your multi-assets here     @multi_asset(         outs={             "asset1": AssetOut(),             "asset2": AssetOut(),         }     )     def my_multi_asset():         # Logic to produce asset1 and asset2         pass      return [my_multi_asset]  # Add the multi-assets to your repository definition my_assets = my_asset_factory()

When adding these assets to your repository definition, you would typically use a function like

define_asset_job

or

to_job

to create jobs that materialize these assets. If you're using a factory pattern, you might have a function that iterates over a configuration or a set of parameters to create multiple

multi_asset

definitions dynamically. If you encounter the error you mentioned in the context of a factory pattern, it could mean that there is a mismatch between the expected asset keys and the actual asset keys produced by the

multi_asset

definitions. Make sure that when you reference these assets elsewhere in your code, you are correctly identifying them by their full asset keys, which include both the asset name and any additional namespace or key prefix specified in the

AssetOut

objects. If you provide a specific code snippet or more details about how you are attempting to load the

multi_asset

via a factory and add it to a definition, I can give you more targeted advice on how to resolve any issues you're facing.