Global Temporary Table

Availability

This feature is available since MogDB 1.1.0.

Introduction

A temporary table does not guarantee persistency. Its life cycle is usually bound to a session or transaction, which can be used to store temporary data during processing and accelerate query.

Benefits

This feature improves the expression capability and usability of temporary tables.

Description

The metadata of the global temporary table is visible to all sessions. After the sessions end, the metadata still exists. The user data, indexes, and statistics of a session are isolated from those of another session. Each session can only view and modify the data submitted by itself.

Global temporary tables have two schemas: ON COMMIT PRESERVE ROWS and ON COMMIT PRESERVE ROWS. In session-based ON COMMIT PRESERVE ROWS schema, user data is automatically cleared when a session ends. In transaction-based ON COMMIT DELETE ROWS schema, user data is automatically cleared when the commit or rollback operation is performed. If the ON COMMIT option is not specified during table creation, the session level is used by default. Different from local temporary tables, you can specify a schema that does not start with pg_temp_ when creating a global temporary table.

Enhancements

The processing of the global temporary table is added based on the local temporary table.

Constraints

• Parallel scanning is not supported.
• Temp tablespace is not supported.
• Partitions are not supported.
• GIST indexes are not supported.
• The user-defined statistics pg_statistic_ext is not supported.
• ON COMMIT DROP is not supported.
• Hash bucket cluster storage is not supported.
• Row store is not supported.

Dependencies

None