Explicit Cache

👤 This documentation is intended for SQL Users on sites that have access to the Cache Infrastructure. The Periscope Cache is part of Data Engine and is an add-on feature. Administrators can reach out to their Customer Success Manager if interested in enabling the Cache Infrastructure for their instance.

Explicit Cache provides the option of directly querying the Periscope Cache. The Explicit Cache feature is available to all customers.

Overview

Queries can be run directly against the cache by selecting the Periscope Cache in the database dropdown menu in the SQL editor.

Caching Data

New tables can be added to the Periscope Cache by navigating to the cache menu via the settings icon in the bottom left corner of the screen. If the cache option is not visible, please reach out to the Customer Success Manager to enable this feature for the account. To import tables into the cache, please follow the instructions on setting caching strategies.

Note: The Periscope Cache is only visible in the database dropdown menu in SQL editors. The Periscope Cache is not shown in the cache menu via the settings icon.

If a table is not cached and is referenced in a query where the Periscope Cache is selected, the following error messages occur:

‍Error message when the schema is referenced

‍Error message when the schema is not referenced

When a query needs to be run directly against a source database, change the database through the database dropdown menu when creating a new chart.

Querying a Cached Table

Explicit Cache only allows for the database display name to be referenced in a query.

Cross-Database Join

When performing a cross-database join, select the Periscope Cache in the database dropdown menu and reference the source databases like the queries below. Please refer to the Cross-Database Joins documentation for more detail.

ExampleOne.Public.Dogs

     

ExampleTwo.Public.Animals

Note: To run queries on the cache or the source database directly, users are required to select the corresponding database in the database dropdown menu (Periscope Cache or the source database). The syntax -- --yes_cache and -- --no_cache is deprecated with Explicit Cache and cannot be used.

Warehouse

Periscope Data Warehouse sites also have the Explicit Cache feature enabled. The Periscope Cache is named "Warehouse" in the database dropdown menu.

Source databases cannot have a display name of "Warehouse" as Periscope Data Warehouse customers have access to Explicit Cache and the Warehouse database specific to Periscope Data Warehouse remains in the dropdown menu.

SQL Materialized Views

By using Explicit Cache, users have the option to allow Periscope to optimize the view by keeping it materialized on the cache. SQL views can be materialized when the Periscope Cache is selected.

Warning Messages

Warning messages specific for Explicit Cache appear when table reference is ambiguous or unqualified.

Ambiguous Tables

If there are two tables with the same name in different schemas, and the schema is not referenced, an Ambiguous Table Reference warning message will be shown.

When there is an ambiguous table reference, the query is run and the Ambiguous Table Reference Warning message informs the users that the query is unpredictable. The first identified table is used, which is not always predictable or the same.

Unqualified Tables

Queries that don’t reference the table with the proper format (“Database_Name.Schema_Name.Table_Name”) return an Unqualified Table warning message. The query can be resolved but are in bad form, because changes to the query or schema can cause the query to break unexpectedly.

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