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.

Queries can be run directly against a source database by selecting the source database through the database dropdown menu in the SQL Editor.

Querying the Periscope Cache

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.

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 using the database name, schema name and table name. 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.

Note: Customers with Periscope Warehouse enabled cannot have a source databases with the display name of "Warehouse".

Error Handling

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

Warning Messages

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

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.

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.

Querying the Source Database

Ensure that the desired database is selected in the database selector on the left hand side of the chart editor.

Error Handling

If a table does not exist on the selected database and is referenced in a query, the following error messages occur:

‍Error message when the schema is referenced

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