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vql to invalidate cache (base views, derived views)

Hi team, I want to find out vql to invalidate cache, I run below for a base views, but it has error "selected view: 'base_view_name' is a base view": ALTER VIEW base_view_name CACHE INVALIDATE it cna only run for derived view: ALTER VIEW derived_view_name CACHE INVALIDATE Also, I am wondering the effect of above vql, it will let the previous cached row no shown through Denodo? or it will also truncate the rows in the configured cached db in Denodo? thank you.
user
26-11-2020 05:14:59 -0500

1 Answer

Hi, ALTER VIEW statement allows you to change various properties of a** derived view.** This is why `ALTER VIEW base_view_name CACHE INVALIDATE`gives you an error since the view is a base view. To modify a base view, you would need to use ALTER TABLE statement instead. For more information, please refer to the [Modifying a Base View](https://community.denodo.com/docs/html/browse/7.0/vdp/vql/creating_a_base_view/modifying_a_base_view/modifying_a_base_view) document. There are two types of cache invalidation: 1. “Full” invalidation, which removes all the cached data for a view. 2. “Partial” invalidation that only removes the cached data that verifies a specified condition. Please note that when a row is marked as invalid or reaches its time to live is not actually removed from the database. The row is in the cache, but when the view is queried, the Execution Engine does not retrieve it from the cache. Cache Maintenance Task” deletes the invalid or expired rows from the tables that hold the cached data of each view. For more information on this, please refer to the [Cache Maintenance Task](https://community.denodo.com/docs/html/browse/7.0/vdp/administration/cache_module/cache_maintenance_task/cache_maintenance_task) document. Hope this helps!
Denodo Team
26-11-2020 16:11:49 -0500
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