View Dependencies
  • 26 Jul 2021
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View Dependencies

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Article Summary

Panoply on Redshift

On Redshift, queries can be saved as tables and then those views can be used like tables.

The saved views rely on tables that you’ve ingested into Panoply (using Panoply data sources or external ingestion tools) and they can also rely on other views that have been created. Saving a view that relies on another view will basically create a chain of views (chain of dependencies). Usually, in these cases, the user will query the last view in that chain (or tree if it’s a more complex configuration) but it’s definitely not a must and you can query each view separately as well.

When working with the classic ETL processes, you create the complete data flow from extraction to how the data will be saved. This entire process is usually saved in the same ingestion tool and is relatively easy to view, examine, and understand. But when you’re working with views, you can easily lose track of the view's flow and what is in charge of what and which view depends on which table/view.

To overcome this issue, the following query can be used to identify the dependencies per view and find the actual dependency tree for your specific setup, just change the view_name_or_table_name and schema_name to match the specific view you’re looking for:

SELECT DISTINCT c_p.oid AS tbloid,
 n_p.nspname AS dependee_schema,
 c_p.relname AS dependee,
 n_c.nspname AS dependent_schema,
 c_c.relname AS dependent,
 c_c.oid AS viewoid
FROM pg_class c_p
 JOIN pg_depend d_p ON c_p.relfilenode = d_p.refobjid
 JOIN pg_depend d_c ON d_p.objid = d_c.objid
 JOIN pg_class c_c ON d_c.refobjid = c_c.relfilenode
 LEFT JOIN pg_namespace n_p ON c_p.relnamespace = n_p.oid
 LEFT JOIN pg_namespace n_c ON c_c.relnamespace = n_c.oid
WHERE d_p.deptype = 'i'
 AND dependee_schema + dependee <> dependent_schema + dependent
 AND dependee = 'view_name_or_table_name'
 AND dependee_schema = 'schema_name';

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