REFRESH MATERIALIZED VIEW

Replaces the contents of a materialized view.

Synopsis

REFRESH MATERIALIZED VIEW [ CONCURRENTLY ] <name>
    [ WITH [ NO ] DATA ]

Description

REFRESH MATERIALIZED VIEW completely replaces the contents of a materialized view. The old contents are discarded. To run this command you must be the owner of the materialized view. With the default, WITH DATA, the materialized view query is run to provide the new data, and the materialized view is left in a scannable state. If WITH NO DATA is specified, no new data is generated and the materialized view is left in an unscannable state. A query returns an error if the query attempts to access the materialized view.

Parameters

CONCURRENTLY : Refresh the materialized view without locking out concurrent selects on the materialized view. Without this option, a refresh that affects a lot of rows tends to use fewer resources and completes more quickly, but could block other connections which are trying to read from the materialized view. This option might be faster in cases where a small number of rows are affected.

This option is only allowed if there is at least one `UNIQUE` index on the materialized view which uses only column names and includes all rows; that is, it must not index on any expressions nor include a `WHERE` clause.

This option cannot be used when the materialized view is not already populated, and it cannot be used with the `WITH NO DATA` clause.

Even with this option, only one `REFRESH` at a time may run against any one materialized view.

name : The name (optionally schema-qualified) of the materialized view to refresh.

WITH [ NO ] DATA : WITH DATA is the default and specifies that the materialized view query is run to provide new data, and the materialized view is left in a scannable state. If WITH NO DATA is specified, no new data is generated and the materialized view is left in an unscannable state. An error is returned if a query attempts to access an unscannable materialized view.

: WITH NO DATA cannot be used with CONCURRENTLY.

Notes

While the default index for future CLUSTER operations is retained, REFRESH MATERIALIZED VIEW does not order the generated rows based on this property. If you want the data to be ordered upon generation, you must use an ORDER BY clause in the materialized view query. However, if a materialized view query contains an ORDER BY or SORT clause, the data is not guaranteed to be ordered or sorted if SELECT is performed on the materialized view.

Examples

This command replaces the contents of the materialized view order_summary using the query from the materialized view’s definition, and leaves it in a scannable state.

REFRESH MATERIALIZED VIEW order_summary;

This command frees storage associated with the materialized view annual_statistics_basis and leaves it in an unscannable state.

REFRESH MATERIALIZED VIEW annual_statistics_basis WITH NO DATA;

Compatibility

REFRESH MATERIALIZED VIEW is a LightDB-A Database extension of the SQL standard.