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Title
# ask-ai
b

Binoy Shah

02/13/2024, 10:25 PM
@Scout what does this error mean
Invariant failed. Description: Tried to retrieve asset key from an assets definition with multiple asset keys
s

Scout

02/13/2024, 10:25 PM
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.
b

Binoy Shah

02/13/2024, 10:27 PM
@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
s

Scout

02/13/2024, 10:27 PM
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:
Copy code
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:
Copy code
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.
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