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#ask-ai
Title
# ask-ai
j

Josh

02/26/2024, 10:33 AM
@Scout check which upstream dependency has been updated when materializing an asset through automaterialization
s

Scout

02/26/2024, 10:33 AM
When using auto-materialization in Dagster, it's important to be aware of the state of upstream dependencies to understand if and why an asset is being materialized. According to the documentation, Dagster provides mechanisms to detect discrepancies between assets and their upstream dependencies, which can help you determine if an upstream asset has been updated. One of the discrepancies that Dagster can raise is the "upstream changed" indicator. This indicator is shown when the most recent materialization of an asset occurred earlier than the most recent materialization of the upstream asset, suggesting that the asset's contents may be stale. In the Dagster UI, assets that have ancestors that have been updated more recently than they have will show a yellow "Upstream data" label. Additionally, there is an issue reported on the Dagster GitHub that discusses the scenario where an asset isn't being auto-materialized because one of its parents is out of date with respect to one of its ancestors. The issue suggests that it would be helpful to link to a filtered view of the asset graph that shows lineage between the node being considered for auto-materialization and the updated ancestor, allowing the user to see the chain of nodes that have the yellow "Upstream data" tag and understand what needs to be updated. While the documentation does not provide a direct method to check which specific upstream dependency has been updated in the context of auto-materialization, the UI indicators and the asset graph can be used to infer this information. If you need more granular control over the materialization process based on the state of upstream assets, you may consider using auto-materialization policies and rules that can be configured to skip materialization under certain conditions, such as when not all parents have been updated. For more detailed and specific use cases, you may need to refer to the latest Dagster documentation or seek assistance from the Dagster community for updates on features that address this need.
j

Josh

02/26/2024, 10:36 AM
@Scout Is there anyway I can do this in code?
s

Scout

02/26/2024, 10:36 AM
As of the last update from the documentation, there isn't a direct code example provided that shows how to programmatically check which specific upstream dependency has been updated when materializing an asset through auto-materialization. However, Dagster does provide a feature called
code_version
which can be used to version assets based on their computation logic. This feature allows you to skip redundant runs of computationally expensive assets by memoizing them based on whether the computation logic of an asset has changed. While this doesn't directly tell you which upstream dependency has changed, it does provide a mechanism to control materialization based on changes in the code. To implement a system that checks for updates in upstream dependencies within your code, you might consider the following approaches: 1. Asset Sensors: You could create sensors that monitor for changes in upstream assets. When an upstream asset is materialized, the sensor could trigger a downstream job or asset to be materialized. 2. Custom Logic: Implement custom logic within your assets that checks the materialization events of upstream assets. This could involve querying the Dagster instance for the materialization metadata of upstream assets and comparing timestamps or other relevant information to determine if an update has occurred. 3. Asset Dependencies: By defining explicit dependencies between assets, Dagster ensures that assets are materialized in the correct order. You could use the dependency graph to determine the order in which assets should be checked for updates. 4. Event Logs: You could also use Dagster's event log to track the materialization of assets. By querying the event log, you could potentially determine which upstream assets have been recently materialized. 5. Asset Materialization Hooks: Implement hooks that get called when an asset is materialized. These hooks could log or take action based on the materialization of upstream assets. Please note that these approaches are conceptual and would require custom implementation based on your specific use case and the capabilities of your Dagster deployment. For the most current and detailed guidance, you should refer to the latest Dagster documentation or seek assistance from the Dagster community.
j

Josh

02/26/2024, 10:38 AM
@Scout how to get the timestamp of last materialization of an upstream asset?
s

Scout

02/26/2024, 10:38 AM
To get the timestamp of the last materialization of an upstream asset, you can use the Dagster instance to query for the latest materialization event of a specific asset. Here's an example of how you might do this in code, based on the documentation:
Copy code
python from dagster import AssetKey, build_op_context  def get_last_materialization_timestamp(context, asset_key):     latest_materialization = context.instance.get_latest_materialization_events(         asset_keys=[AssetKey(asset_key)]     )     if latest_materialization and asset_key in latest_materialization:         return latest_materialization[asset_key].timestamp     else:         return None  # Example usage: with build_op_context() as context:     timestamp = get_last_materialization_timestamp(context, "your_upstream_asset_key")     print(f"The last materialization of the upstream asset occurred at: {timestamp}")
In this example,
AssetKey("your_upstream_asset_key")
should be replaced with the actual key of your upstream asset. The
get_latest_materialization_events
method returns a dictionary mapping
AssetKey
to the latest materialization event for that asset. You can then access the
timestamp
attribute of the event to get the time of the last materialization. Please ensure that you have the appropriate context and that your Dagster instance is properly configured to access the event logs. The exact implementation details may vary depending on the version of Dagster you are using and the setup of your environment. Always refer to the latest documentation for the most accurate and up-to-date information.
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