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Oracle 视图 V$SQL_JOIN_FILTER 官方解释，作用，如何使用详细说明

本站中文解释

Oracle视图V$SQL_JOIN_FILTER是用来描述SQL查询中过滤器的信息的视图。它着眼于已被计划的SQL语句的详细信息，它的列包括： sql_id， which_tables目标表，column_position过滤器在哪一列，join_expressionJOIN表达式，及其他过滤器功能相关信息。

V$SQL_JOIN_FILTER通常会用于查找SQL查询中JOIN和WHERE子句存在什么过滤器条件以及JOIN子句中都有哪些表，以及它们是如何连接的，并识别是否存在JOIN条件丢失的问题。

使用下列语句可以查看SQL查询的JOIN过滤器信息：
SELECT *
FROM v$sql_join_filter
WHERE sql_id = ‘&Sql_id’;

官方英文解释

V$SQL_JOIN_FILTER displays performance information about the characteristics of join filters when they are used for a parallel cursor. (A join filter is a bitmap filter applied to table rows before a join operation in order to avoid parallel communication.)

Column Datatype Description

QC_SESSION_ID

NUMBER

QC (Query Coordinator) session ID of the given cursor for the given parallel query

QC_INSTANCE_ID

NUMBER

QC (Query Coordinator) instance ID of the given cursor for the given parallel query

SQL_PLAN_HASH_VALUE

NUMBER

SQL plan hash value of the given cursor for the given parallel query

FILTER_ID

NUMBER

An ID that identifies the join filter in the given cursor and corresponds to the filter ID in the execution plan

LENGTH

NUMBER

Total size of the join filter field

BITS_SET

NUMBER

Number of bits set in this filter

FILTERED

NUMBER

Number of rows seen by the join filter

PROBED

NUMBER

Number of rows of the right table that have been tested against the bitmap filter. This is the sum of the filtered rows plus the non-filtered rows.

ACTIVE

NUMBER

Whether the filter is active (Yes) or not (No)

CON_ID

NUMBER

The ID of the container to which the data pertains. Possible values include:

  • 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.

  • 1: This value is used for rows containing data that pertain to only the root

  • n: Where n is the applicable container ID for the rows containing data


数据运维技术 » Oracle 视图 V$SQL_JOIN_FILTER 官方解释，作用，如何使用详细说明
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