@Scout How to get asset metadata from materialize

To get asset metadata from a materialization in Dagster, you can use the

AssetMaterialization

event to attach metadata to an asset when it is materialized. This metadata can then be accessed in various ways, depending on where you need to use it. Here's an example of how you might emit an

AssetMaterialization

event with metadata when materializing an asset:

python from dagster import AssetMaterialization, MetadataValue, op, OpExecutionContext  @op def my_metadata_materialization_op(context: OpExecutionContext):     df = read_df()     remote_storage_path = persist_to_storage(df)     context.log_event(         AssetMaterialization(             asset_key="my_dataset",             description="Persisted result to storage",             metadata={                 "text_metadata": "Text-based metadata for this event",                 "path": MetadataValue.path(remote_storage_path),                 "dashboard_url": MetadataValue.url(                     "<http://mycoolsite.com/url_for_my_data>"                 ),                 "size (bytes)": calculate_bytes(df),             },         )     )     return remote_storage_path

In this example, the

my_metadata_materialization_op

op reads some data, persists it to storage, and then logs an

AssetMaterialization

event with metadata about the storage path, a URL to a dashboard, and the size of the data in bytes. To access this metadata later, you can use the Dagster instance to query the event log for materialization events. Here's an example of how you might do this within another asset:

python from dagster import asset, AssetKey, DagsterInstance  @asset def downstream_asset():     instance = DagsterInstance.get()     materialization = instance.get_latest_materialization_event(AssetKey(["my_dataset"])).asset_materialization     metadata = materialization.metadata     # Now you can use the metadata as needed

In this example,

downstream_asset

uses the

DagsterInstance.get()

method to get the current Dagster instance and then queries for the latest materialization event for the asset with the key

my_dataset

. It then accesses the metadata from this materialization event. Please note that the exact method to access the metadata may vary depending on the context in which you're working (e.g., within an asset, op, or sensor) and whether the asset is partitioned or not. The provided examples are based on the documentation and should be adapted to fit the specific requirements of your Dagster project.