![]() DISTINCT aggregate functions, such as DISTINCT COUNT, DISTINCT SUM, and so on. ![]() The COUNT, SUM, MIN, MAX, and AVG aggregate functions are supported. Aggregate functions: MEDIAN, PERCENTILE_CONT, LISTAGG, STDDEV_SAMP, STDDEV_POP, APPROXIMATE COUNT, APPROXIMATE PERCENTILE, and bitwise aggregate functions.UNION ALL when it occurs in a subquery and an aggregate function or a GROUP BY clause is present in the query.Set operations: UNION, INTERSECT, EXCEPT, MINUS.For more information about events and state changes, see STL_MV_STATE.Īmazon Redshift currently doesn't support incremental refresh for materialized views that are defined with a query using any of the following SQL elements: Examples of such operations are a manually invoked VACUUM, a classic resize, an ALTER DISTKEY operation, an ALTER SORTKEY operation, and a truncate operation. Some user-initiated operations on base tables force a materialized view to be fully recomputed next time that a REFRESH operation is run.For more information about events and state changes, see STL_MV_STATE. For information about VACUUM, see VACUUM. When this vacuum operation happens, any dependent materialized views are marked for recomputation upon the next refresh (even if they are incremental). After an internally defined threshold period, a vacuum operation is allowed to run. Background vacuum operations might be blocked if materialized views aren't refreshed.Some of these operations might force a REFRESH MATERIALIZED VIEW operation to fully recompute the materialized view even though the query defining the materialized view only uses the SQL features eligible for incremental refresh. Some operations in Amazon Redshift interact with materialized views. Depending on the input argument type, Amazon Redshift still supports incremental refresh for materialized views for the following functions with specific input argument types: DATE (timestamp), DATE_PART (date, time, interval, time-tz), DATE_TRUNC (timestamp, interval).For a full refresh of a materialized view, REFRESH MATERIALIZED VIEW sees all base table rows visible to the refresh transaction, according to usual Amazon Redshift transaction semantics.Therefore, if the refresh operation runs after a data manipulation language (DML) statement in the same transaction, then changes of that DML statement aren't visible to refresh. For incremental materialized views, REFRESH MATERIALIZED VIEW uses only those base table rows that are already committed.Amazon Redshift transaction semantics are followed to determine what data from base tables is visible to the REFRESH command, or when the changes made by the REFRESH command are made visible to other transactions running in Amazon Redshift. The REFRESH MATERIALIZED VIEW command runs as a transaction of its own. Furthermore, the owner must have SELECT privilege on the underlying base tables to successfully run REFRESH MATERIALIZED VIEW. Only the owner of a materialized view can perform a REFRESH MATERIALIZED VIEW operation on that materialized view. The name of the materialized view to be refreshed. ![]()
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