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What is fast refresh materialized view in Oracle?
Fast refresh for a materialized view containing joins and aggregates is possible after any type of DML to the base tables (direct load or conventional INSERT , UPDATE , or DELETE ). It can be defined to be refreshed ON COMMIT or ON DEMAND .
How long does it take to refresh a materialized view?
The simplest form to refresh a materialized view is a Complete Refresh. It loads the contents of a materialized view from scratch. This means, if the SQL query of the materialized view has an execution time of two hours, the Complete Refresh takes at least two hours as well – or ofter even longer.
How does materialized view improve performance in Oracle?
Materialized views improve query performance by precalculating expensive join and aggregation operations on the database prior to execution and storing the results in the database. The query optimizer automatically recognizes when an existing materialized view can and should be used to satisfy a request.
What is fast refresh?
Fast Refresh is an implementation of Hot Reloading with full support from React. It replaces unofficial solutions like react-hot-loader . With Fast Refresh, changes to the code for your React components immediately update in the browser, without losing component state.
How materialized view helps in performance?
Which is better materialized view or view?
The performance of Materialized view it is better than normal View because the data of materialized view will be stored in table and table may be indexed so faster for joining also joining is done at the time of materialized views refresh time so no need to every time fire join statement as in case of view.
Why materialized view is faster than table?
A materialized view is a pre-computed data set derived from a query specification (the SELECT in the view definition) and stored for later use. Because the data is pre-computed, querying a materialized view is faster than executing a query against the base table of the view.
When should I use on commit fast refresh in Oracle?
If you anticipate performing insert, update or delete operations on tables referenced by a materialized view concurrently with the refresh of that materialized view, and that materialized view includes joins and aggregation, Oracle recommends you use ON COMMIT fast refresh rather than ON DEMAND fast refresh.
Why is the materialized view not fast refreshable?
The materialized view is not fast refreshable because DML has occurred to a table on which PCT fast refresh is not possible. To avoid this occurring, Oracle recommends performing a fast refresh immediately after any partition maintenance operation on detail tables for which partition tracking fast refresh is available.
How to optimize refresh in Oracle Database?
If set to FALSE, Oracle can optimize refresh by using parallel DML and truncate DDL on a materialized views. When a materialized view is refreshed in atomic mode, it is eligible for query rewrite if the rewrite integrity mode is set to stale_tolerated. Atomic refresh cannot be guaranteed when refresh is performed on nested views.
What are the requirements for materialized view log in Oracle?
1) An Oracle materialized view log must be present for each base table. 2) The RowIDs of all the base tables must appear in the SELECT list of the MVIEW query definition. 3) If there are outer joins, unique constraints must be placed on the join columns of the inner table.