Oracle教程 2023-02-24

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