Oracle 视图 DBA_HIST_SQL_PLAN 官方解释，作用，如何使用详细说明

视图

Oracle的DBA_HIST_SQL_PLAN视图是Oracle数据库提供的一个系统视图，可以用来查看实例中保存在AWR(数据库自动性能统计)历史计划数据中SQL 语句执行计划的历史记录，其中包括SQL_ID,PLAN_HASH_VALUE,OPERATION,OPTIONS,OBJECT_NODE, OPTIMIZER_COST。这些都可用来查询是否有变化，根据这些参数比较优化的可能性。

要使用DBA_HIST_SQL_PLAN视图，可以使用标准SQL查询，首先在PL/SQL环境中连上实例，然后执行此视图的查询语句，可以查看指定的SQL语句的历史计划，以检查历史执行计划的变化，并且根据这些参数考虑合适的优化方案。

例如，下面的SQL用来查询SQL_ID为“3rk666qh3q2g2”执行历史计划。

SELECT
sql_id,
plan_hash_value,
operation,
options,
object_node,
optimizer_cost
FROM dba_hist_sql_plan
WHERE sql_id = 3rk666qh3q2g2

官方英文解释

DBA_HIST_SQL_PLAN displays the execution plan information for each child cursor in the workload repository.

This view captures information from V$SQL_PLAN and is used with the DBA_HIST_SQLSTAT view.

Numerical representation of the SQL plan for the cursor. Comparing one PLAN_HASH_VALUE to another easily identifies whether or not two plans are the same (rather than comparing the two plans line by line).

Name of the internal operation performed in this step (for example, TABLE ACCESS)

A variation on the operation described in the OPERATION column (for example, FULL)

Name of the database link used to reference the object (a table name or view name). For local queries that use parallel execution, this column describes the order in which output from operations is consumed.

Current mode of the optimizer for the first row in the plan (statement line), for example, ALL_ROWS. When the operation is a database access (for example, TABLE ACCESS), this column indicates whether or not the object is analyzed.

Depth (or level) of the operation in the tree. It is not necessary to issue a CONNECT BY statement to get the level information, which is generally used to indent the rows from the PLAN_TABLE table. The root operation (statement) is level 0.

Number of index columns with start and stop keys (that is, the number of columns with matching predicates)

Cost of the operation as estimated by the optimizer s cost-based approach. For statements that use the rule-based approach, this column is null.

Estimate, by the cost-based optimizer, of the number of rows produced by the operation

Estimate, by the cost-based optimizer, of the number of bytes produced by the operation

Step that computes the pair of values of the PARTITION_START and PARTITION_STOP columns

Other information specific to the execution step that users may find useful. See EXPLAIN PLAN for values.

Stores the method used to distribute rows from producer query servers to consumer query servers

CPU cost of the operation as estimated by the optimizer s cost-based approach. For statements that use the rule-based approach, this column is null.

I/O cost of the operation as estimated by the optimizer s cost-based approach. For statements that use the rule-based approach, this column is null.

Temporary space usage of the operation (sort or hash-join) as estimated by the optimizer s cost-based approach. For statements that use the rule-based approach, this column is null.

Predicates used to locate rows in an access structure. For example, start or stop predicates for an index range scan.

Elapsed time (in seconds) of the operation as estimated by the optimizer s cost-based approach. For statements that use the rule-based approach, this column is null.

Provides extra information specific to an execution step of the execution plan. The content of this column is structured using XML because it allows multiple pieces of information to be stored, including the following:

Name (if any) of the outline or the SQL profile used to build the execution plan

The outline data, a set of optimizer hints that can be used to regenerate the same plan

0: This value is used for rows containing data that pertain to the entire CDB. This value is also used for rows in non-CDBs.

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数据库远程运维 Oracle 视图 DBA_HIST_SQL_PLAN 官方解释，作用，如何使用详细说明