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Title
# ask-ai
j

Jason Gofford

03/05/2024, 10:16 AM
How do I define an upstream asset in dagster-dbt, if the upstream asset has a prefix_key?
s

Scout

03/05/2024, 10:16 AM
To define an upstream asset in Dagster with a
key_prefix
, you would typically use the
@asset
decorator and specify the
key_prefix
argument. When you want to define dependencies between assets, you can use the
deps
argument within the
@asset
decorator to specify upstream assets. Here's an example from the documentation that shows how you might define an upstream asset with a
key_prefix
and a downstream asset that depends on it:
Copy code
python from dagster import asset, AssetKey  @asset(key_prefix="prefix") def upstream():     # ... upstream computation ...  @asset(deps={"upstream": AssetKey(["prefix", "upstream"])}) def downstream(upstream):     # ... downstream computation that depends on upstream ...
In this example, the
upstream
asset is defined with a
key_prefix
of
"prefix"
, which means its full asset key will be
AssetKey(["prefix", "upstream"])
. The
downstream
asset then specifies its dependency on the
upstream
asset by providing a dictionary to the
deps
argument, where the key is the argument name (
"upstream"
) and the value is the
AssetKey
of the upstream asset. If you are integrating with dbt and want to define a dbt asset as an upstream dependency of a non-dbt asset, you can use the
DbtManifest
class to fetch the asset key of a given source or model. This allows you to reference dbt models directly without having to manually construct the asset key. Here's an example from the documentation:
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python from dagster_dbt import dbt_cli_resource, dbt_assets  manifest = dbt_cli_resource.configured({"project_dir": "path/to/dbt/project"}).manifest  @dbt_assets(manifest=manifest) def my_dbt_assets():     ...  @asset(non_argument_deps={manifest.get_asset_key_for_model("my_dbt_model")}) def downstream_asset():     # ... downstream computation that depends on a dbt model ...
In this example,
my_dbt_assets
is a collection of dbt assets loaded from a dbt project, and
downstream_asset
is a non-dbt asset that depends on a dbt model named
"my_dbt_model"
. The
non_argument_deps
argument is used to specify the dependency on the dbt model by using the
get_asset_key_for_model
method from the
DbtManifest
object. Please note that the exact syntax and methods may vary depending on the version of Dagster and dagster-dbt you are using, so it's important to refer to the specific documentation for your version to ensure you are using the correct API.
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