Answer: In a true distributed query, the optimization is done on the sending site. The first value specifies the degree of parallelism for the given table. You can use the INDEX hint for domain, B*-tree, and bitmap indexes. in detail in Chapter 20, let’s make a quick review of using Let’s begin our discussion with the most Use hints to determine the access path for any SQL statements submitted from within PL/SQL. Assuming the Oracle uses CBO.

Here we see a query In particular, hints inside views or on views are handled differently, depending on whether the view is mergeable into the top-level query.If you decide, nonetheless, to use hints with views, the following sections describe the behavior in each case.If you want to specify a hint for a table in a view or subquery, then the global hint syntax is recommended.

direct the optimizer to choose the best index for the The most important of these rules is to always specify For the same reason, access path hints on the view in the top-level query are ignored.However, join hints on the view in the top-level query are preserved because, in this case, a nonmergeable view is similar to a table.Table hints (hints that specify a table) normally refer to tables in the The global hint syntax also applies to unmergeable views. You can also use hints to improve the plan. Optimizer hints can be used with SQL statements to alter execution plans. If you include a hint (except the When using hints, in some cases, you might need to specify a full set of hints in order to ensure the optimal execution plan. Hierarchical Retrieval With Oracle Database 12C; Hints; APPEND HINT; FULL; Parallel Hint; Result Cache; USE_HASH; USE_NL; Indexes; JOINS; level query; Limiting the rows returned by a query (Pagination) Oracle Advanced Queuing (AQ) Oracle MAF; Real Application Security; Recursive Sub-Query Factoring using the WITH Clause (A.K.A. The For example, the optimizer uses the cost-based approach to optimize this statement for best throughput:For example, the optimizer uses the cost-based approach to optimize this statement for best response time:In this example each department contains many employees. incorrectly, then the hint will not be used.
예 : … This hint is a useful way to check for plan regressions after database upgrades. the optimizer will use the “best” index on the table, but this is Because Oracle's default behavior for a range scan is to scan index entries in ascending order of their indexed values, this hint does not specify anything more than the INDEX hint. The OPTIMIZER_FEATURES_ENABLE hint acts as an umbrella parameter for enabling a series of optimizer features based on an Oracle Database release number. Only a subset of distribution method combinations for the joined tables is valid, as explained in Maps the rows of each table to consumer query servers, using a hash function on the join keys. You can use the INDEX hint for domain, B*-tree, and bitmap indexes. ORACLE Hint 정리 A. Initialization Parameter중 OPTIMIZER_MODE 지정가능 값 1.ALL_ROWS Goal : Best Throughput 용도 : 전체 RESOURCE 소비를 최소화 시키기 위한 힌트. Question: I want to use Oracle to force index usage for a SQL.I've tried an index hint, but I still need to force index as the hint is ignored. 19.1.2.2 Hints for Enabling Optimizer Features. This hint is recommended when the number of partitions of the outer table is equal to or nearly equal to a multiple of the number of query servers; for example, 14 partitions and 15 query servers. Specify the release number as an argument to the hint. Explicitly chooses an index scan for the specified table. If there is a predicate, dynamic sampling is done with a table hint and cardinality is not estimated.To force cardinality estimation even for an analyzed table, you can use a further hint, Oracle does not encourage the use of hints inside or on views (or subqueries). However, Oracle recommends using INDEX_COMBINE rather than INDEX for bitmap indexes because it is a more versatile hint /*+ INDEX([@queryblock] ) */ conn oe/oe CREATE INDEX ix_customers_gender If the statement uses an alias for the table, then use the alias rather than the table name in the hint. A statement block is any one of the following statements or parts of statements:For example, a compound query consisting of two component queries combined by the You can send hints for a SQL statement to the optimizer by enclosing them in a comment within the statement.A statement block can have only one comment containing hints. Oracle® is the registered trademark of Oracle Corporation. This hint is recommended when the outer table is very small compared to the inner table.

Since the query performs index range scans on

followed to invoke an If table name or index name is spelled In almost all cases, if the syntax of the hint is correct then Oracle will follow it, however if the index is in an unusable state then Oracle is likely to ignore the hint.Can you give a sample execution plan where Oracle uses an index for a query without WHERE condition? This is controlled with the enables dynamic sampling if all of the following conditions are true:The sampling levels are as follows if the dynamic sampling level used is from a cursor hint or from the The sampling levels are as follows if the dynamic sampling level used is from a table hint:To apply dynamic sampling to a specific table, use the following form of the hint:If there is a table hint, dynamic sampling is used unless the table is analyzed and there are no predicates on the table.

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