Oracle materialized hint

How to create and manage views in Oracle? What are hints in Oracle? The Oracle materialize hint is used to ensure that the Oracle cost-based optimizer materializes the temporary tables that are created inside the WITH clause.

This is not necessary in Oracle10g, but it helps ensure that the tables are only created one time. Note: You may find a faster execution plan by using Global Temporary tables, depending. If the query runs every time when the user uses it then how materalized hint helps in faster performance. Please answer the question and if my understanding is wrong please correct it. You can then reference the subquery block multiple places in the query by specifying the query name.

Oracle Database optimizes the query by treating the query name as an inline view. When you use the materialize hint , it instructs the optimiser to create a global temporary table and insert the data generated by the query in the with clause into it. Wherever the query is referenced in the rest of the query, it will select the from the global temporary table instead of rerunning the statement.

WITH clause is commonly used to simplify SQL statements. A WITH subquery would be materialized for EACH QUERY execution. It would be materialized 0times in the above scenario. This undocumented hint causes Oracle to put the query block that was hinted as materialize into a temporary table for the duration of the query - and then that data is removed.

If you use REWRITE with a view list and the list contains an eligible materialized view, then Oracle uses that view regardless of its cost. Oracle does not consider views outside of the list. If you do not specify a view list, then Oracle searches for an eligible materialized view and always uses it regardless of the cost of the final plan.

USE_NL The USE_NL hint causes Oracle to join each specified table to another row source with a nested loops join, using the specified table as the inner table. We can see what is happening under the covers using SQL trace. In Oracle 12c if I call a function in a query that uses MATERIALIZE hint in a WITH.

The complication comes from the lag between the last refresh of the materialized view and subsequent DML changes to the base tables. The NO_MERGE hint causes Oracle not to merge mergeable views. This hint is most often used to reduce the number of possible permutations for a query and make optimization faster. FACT The FACT hint indicated that the table should be considered as a fact table. This is used in the context of the star transformation.

With the INLINE hint you can prevent the materialization, which in turn means that Oracle can eliminate partitions, if the underlying tables are partitioned appropriately, or access data through indexes, meaning that it does not have to compute the factored subquery for all values before it filters. Also often redundant is the NOCACHE hint, since this places blocks at the tail of the LRU list, which is also Oracle’s default behaviour with the majority of blocks. Some OLTP applications also benefit from materialized views involving non-volatile data.

By themselves, Oracle views, materialized views, and SQL query hints are useful tools for Oracle tuning. Materialized views provide performance benefits to data warehouse applications. I need to put an index on a materialized view. I do not know how often the stats are refreshed and would this effect it performance of the index or view? To that end Oracle introduced the PQ_SKEW(tab_name_or_alias) hint , which informs the optimizer of data skew in the join keys.

To show the format the SELECT statement only will be use but the format is identical for all three commands. If we change DOP to for same query, then ideally the same query with parallel hint will take second. Similarly using DOP as will take seconds.

I started wondering what might cause a NO_INDEX hint to not work as expected. The ORDERED hint gives the user the ability to shuffle the tables on the FROM clause. Directing Oracle to join the tables in a specific order will alter the order of the joins.

This is the first thing that should be done when tuning SQL. Put this hint in and shuffle the tables around on the FROM clause.