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Title
# ask-ai
g

Greg H

03/13/2024, 10:46 PM
Dagster integrates well with Sling-CLI. When using a replication.yaml for Sling, can I set the schema for the streams dynamically? In my test database, I'm using a snapshot that is stored in a schema that's different from my production schema.
s

Scout

03/13/2024, 10:46 PM
We provide a framework for building ELT pipelines with Dagster through helpful asset decorators and resources, including an integration with Sling, which allows you to sync data between databases and file systems. When using Sling with Dagster, you typically define a
replication.yaml
file that specifies the source and target connections, as well as which streams to sync from. The
replication.yaml
file or its equivalent Python dictionary allows you to set various configurations for your replication job, including the
defaults
section where you can specify the naming pattern for the objects (tables) that will be created or updated in the target. Here's an example snippet from the documentation:
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yaml defaults:   mode: full-refresh   object: "{stream_schema}_{stream_table}"
In this configuration, the
object
key allows you to define a naming pattern that includes placeholders for the schema and table names (
{stream_schema}
and
{stream_table}
). This pattern is used to construct the names of the objects in the target. However, the documentation does not explicitly mention the ability to dynamically set the schema for streams in the
replication.yaml
file based on different environments like test or production. Typically, the schema would be set as part of the stream configuration and would not change dynamically. If you need to use different schemas for different environments (such as test and production), you might consider maintaining separate
replication.yaml
files for each environment or using environment variables to configure the schema names within your replication configuration if Sling supports that functionality. For more dynamic control over the schema, you might need to look into Sling's own documentation or consider implementing a custom solution that can dynamically adjust the
replication.yaml
configuration based on the environment you are running in. If you have further questions or need more specific guidance, please refer to the Sling documentation or reach out to the Sling community for more details on dynamic schema configuration.
g

Greg H

03/13/2024, 10:57 PM
@Scout how can I rename an asset that I define in a replication.yaml?
s

Scout

03/13/2024, 10:57 PM
Renaming an asset in Dagster, particularly one that is defined in a
replication.yaml
file used by Sling, involves a few considerations. As of my knowledge cutoff date, Dagster does not have built-in support for renaming assets while preserving their history. This means that if you change the name of an asset, Dagster will treat it as a new asset without the historical runs and materializations of the old asset name. However, if you need to rename an asset, you can do so by updating the
replication.yaml
file to reflect the new name in the relevant sections. Here's a general approach: 1. Update the
replication.yaml
file to change the name of the asset in the target configuration. This might involve changing the
object
naming pattern or the specific stream configuration that sets the name of the target table or object. 2. Update your Dagster asset definitions to reflect the new asset name. If you are using the
sling_assets
decorator provided by the
dagster_embedded_elt
package, you would update the asset definitions in your Dagster code to use the new names. 3. If you want to preserve the history of the renamed asset, you would need to handle this manually. This could involve migrating data from the old asset to the new one or creating a custom solution to map the historical data to the new asset name. 4. After making the changes, you would redeploy your Dagster pipeline with the updated asset definitions. Here's an example of how you might define assets using Sling in Dagster:
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python
from dagster_embedded_elt import sling
from dagster_embedded_elt.sling import (
    DagsterSlingTranslator,
    SlingResource,
    sling_assets,
)

from dagster import Definitions, file_relative_path

replication_config = file_relative_path(__file__, "../sling_replication.yaml")
sling_resource = SlingResource(connections=[...])  # Add connections here

@sling_assets(replication_config=replication_config)
def my_assets(context, sling: SlingResource):
    yield from sling.replicate(
        replication_config=replication_config,
        dagster_sling_translator=DagsterSlingTranslator(),
    )
    for row in sling.stream_raw_logs():
        <http://context.log.info|context.log.info>(row)

defs = Definitions(
    assets=[
        my_assets,
    ],
    resources={
        "sling": sling_resource,
    },
)
In this example, if you wanted to rename
my_assets
, you would update the
replication.yaml
file and the asset definition in the Python code. Please note that the exact steps for renaming an asset may vary depending on the specifics of your implementation and the capabilities of Sling. Always ensure that you have a backup of your data and consider the implications of renaming assets on your downstream consumers and processes. If you need further assistance, please consult
the Sling documentation or reach out to their support channels.