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persist_for (for Derived Tables)

This page refers to the persist_for parameter that is part of a derived_table

persist_for can also be used as part of an explore, described here

persist_for can also be used as part of a model, described here

Usage

view: my_view {
  derived_table: {
    persist_for: "24 hours"
    …
  }
}

Hierarchy

persist_for

Default Value

None

Accepts

A string containing an integer followed by a timeframe (seconds, minutes, or hours)

Definition

Consider instead using a datagroup and datagroup_trigger, as described on this page about caching.

persist_for lets you set the maximum amount of time that a persistent derived table may be used before it is regenerated. When a user runs a query that relies on a persist_for derived table, Looker checks the age of the table against persist_for. If the age is greater than the persist_for setting, the derived table is regenerated before the query is run. If the age is less than the persist_for setting, the existing derived table is used.

If your admin has given you the develop permission, you can force a derived table to regenerate before its persist_for age has been reached. Select the Rebuild Derived Tables & Run option from the Explore Gear drop-down menu, which you’ll find in the upper right of the screen after running a query:

Examples

Regenerate the derived table if it is older than 1 hour

persist_for: "1 hour"

Regenerate the derived table if it is older than 1.5 hours

persist_for: "90 minutes"

Regenerate the derived table if it is older than 1 day

persist_for: "24 hours"

Common Challenges

persist_for Requires That You Have Enabled Persistent Derived Tables

persist_for will have no effect unless you have enabled persistence for derived tables on your Looker instance. Most customers do set up persistent derived tables when they initially configure Looker. The most common exception to this rule is for customers that connect Looker to a PostgreSQL read-only, hot-swap slave.

persist_for Works Differently Between Development Mode And Production Mode

persist_for should work as expected when in production mode. When in development mode all derived tables are persisted for a maximum of 24 hours, even if you set persist_for to a longer value.

Things to Know

Alternatives to persist_for

Once the persist_for timeframe expires, Looker does not automatically regenerate a new derived table. Rather, the table is dropped, and a new derived table will be generated the next time a user queries it. Instead of waiting for a user query to trigger the generation of a derived table, you can schedule the automatic regeneration of a derived table using sql_trigger_value.

Using datagroups with datagroup_trigger, incorporates the functionality of both persist_for and sql_trigger_value. Datagroups can also be used to manage caching for queries that are not based on a PDT. See this page about caching for more information.

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