Which parameter is more powerful for defining local caching policies in Looker?

The parameter that is more powerful for defining local caching policies in Looker is persist_for. This parameter allows developers to specify how long the results of a query should be cached on the Looker server. By setting a duration for the caching period, you can optimize performance and manage data freshness according to the needs of your organization. Essentially, it helps balance the trade-off between performance (by reducing the load on the underlying data sources through caching) and the need for data accuracy and timeliness.

In contrast, while the other parameters have their purposes, they don't specifically address caching policies in the same way. For instance, grow_shrink deals with varying the size of persistent caches based on usage patterns, sql_trigger helps determine when a persistent derived table should be rebuilt based on changes in the underlying data, and datagroup is used to manage the state of data considering how often it gets refreshed. However, none of these directly provide a robust mechanism for controlling the duration of how long data should be kept cached. This makes persist_for a crucial parameter for effectively managing local caching policy in Looker.