如何在视图中获取列级依赖项

Question

我已经就此事做了一些研究,但还没有解决方案.我想得到的是视图中的列级依赖项.所以,假设我们有一个这样的表

create table TEST(
    first_name varchar(10),
    last_name varchar(10),
    street varchar(10),
    number int
)

和这样的观点:

create view vTEST
as
    select
        first_name + ' ' + last_name as [name],
        street + ' ' + cast(number as varchar(max)) as [address]
    from dbo.TEST

我想要的是得到这样的结果:

column_name depends_on_column_name depends_on_table_name
----------- --------------------- --------------------
name        first_name            dbo.TEST
name        last_name             dbo.TEST
address     street                dbo.TEST
address     number                dbo.TEST

我已尝试过sys.dm_sql_referenced_entities功能,但referencing_minor_id视图总是为0.

select
    referencing_minor_id,
    referenced_schema_name + '.' + referenced_entity_name as depends_on_table_name,
    referenced_minor_name as depends_on_column_name
from sys.dm_sql_referenced_entities('dbo.vTEST', 'OBJECT')

referencing_minor_id depends_on_table_name depends_on_column_name
-------------------- --------------------- ----------------------
0                    dbo.TEST              NULL
0                    dbo.TEST              first_name
0                    dbo.TEST              last_name
0                    dbo.TEST              street
0                    dbo.TEST              number

sys.sql_expression_dependencies过时也是如此sys.sql_dependencies.

我错过了什么或不可能做到的？

有一些相关的问题(查找视图中使用的别名的真实列名？),但正如我所说 - 我还没有找到一个有效的解决方案.

编辑1:我试图使用DAC来查询此信息是否存储在系统基表中的某个位置但未找到它

Answer 1

此解决方案只能部分回答您的问题.它不适用于表达式的列.

您可以使用sys.dm_exec_describe_first_result_set来获取列信息:

@include_browse_information

如果设置为1,则分析每个查询,就好像它在查询上有FOR BROWSE选项一样.返回其他键列和源表信息.

CREATE TABLE txu(id INT, first_name VARCHAR(10), last_name VARCHAR(10));
CREATE TABLE txd(id INT, id_fk INT, address VARCHAR(100));

CREATE VIEW v_txu
AS
SELECT t.id AS PK_id,
       t.first_name  AS name,
       d.address,
       t.first_name + t.last_name AS name_full
FROM txu t
JOIN txd d
  ON t.id = d.id_fk

主要查询:

SELECT name, source_database, source_schema,
      source_table, source_column 
FROM sys.dm_exec_describe_first_result_set(N'SELECT * FROM v_txu', null, 1) ;  

输出:

+-----------+--------------------+---------------+--------------+---------------+
|   name    |   source_database  | source_schema | source_table | source_column |
+-----------+--------------------+---------------+--------------+---------------+
| PK_id     | fiddle_0f9d47226c4 | dbo           | txu          | id            |
| name      | fiddle_0f9d47226c4 | dbo           | txu          | first_name    |
| address   | fiddle_0f9d47226c4 | dbo           | txd          | address       |
| name_full | null               | null          | null         | null          |
+-----------+--------------------+---------------+--------------+---------------+

DBFiddleDemo

Answer 2

它是基于查询计划的解决方案.它有一些冒险

• 几乎所有选择的查询都可以处理
• 没有SchemaBinding

和不满

• 尚未经过适当的测试
• 如果Microsoft更改XML查询计划,可能会突然崩溃.

核心思想是XML查询计划中的每个列表达式都在"DefinedValue"节点中定义."DefinedValue"的第一个子节点是对输出列的引用,第二个是表达式.表达式根据输入列和常量值计算.如上所述,它仅基于经验观察,需要进行适当的测试.

这是一个调用示例:

exec dbo.GetColumnDependencies 'select * from dbo.vTEST'

target_column_name | source_column_name        | const_value
---------------------------------------------------
address            | Expr1007                  | NULL
name               | Expr1006                  | NULL
Expr1006           | NULL                      | ' '
Expr1006           | [testdb].[dbo].first_name | NULL
Expr1006           | [testdb].[dbo].last_name  | NULL
Expr1007           | NULL                      | ' '
Expr1007           | [testdb].[dbo].number     | NULL
Expr1007           | [testdb].[dbo].street     | NULL

这是代码.首先得到XML查询计划.

declare @select_query as varchar(4000) = 'select * from dbo.vTEST' -- IT'S YOUR QUERY HERE.
declare @select_into_query    as varchar(4000) = 'select top (1) * into #foo from (' + @select_query + ') as src'
      , @xml_plan             as xml           = null
      , @xml_generation_tries as tinyint       = 10
;
while (@xml_plan is null and @xml_generation_tries > 0) -- There is no guaranty that plan will be cached.
begin 
  execute (@select_into_query);
  select @xml_plan = pln.query_plan
    from sys.dm_exec_query_stats as qry
      cross apply sys.dm_exec_sql_text(qry.sql_handle) as txt
      cross apply sys.dm_exec_query_plan(qry.plan_handle) as pln
    where txt.text = @select_into_query
  ;
end
if (@xml_plan is null
) begin
    raiserror(N'Can''t extract XML query plan from cache.' ,15 ,0);
    return;
  end
;

接下来是一个主要查询.它最大的部分是用于列提取的递归公用表表达式.

with xmlnamespaces(default 'http://schemas.microsoft.com/sqlserver/2004/07/showplan'
                  ,'http://schemas.microsoft.com/sqlserver/2004/07/showplan' as shp -- Used in .query() for predictive namespace using. 
)
    , cte_column_dependencies as
    (

递归的种子是一个查询,它提取存储1行感兴趣的选择查询的#foo表的列.

select
    (select foo_col.info.query('./ColumnReference') for xml raw('shp:root') ,type) -- Becouse .value() can't extract attribute from root node.
      as target_column_info
  , (select foo_col.info.query('./ScalarOperator/Identifier/ColumnReference') for xml raw('shp:root') ,type)
      as source_column_info
  , cast(null as xml) as const_info
  , 1 as iteration_no
from @xml_plan.nodes('//Update/SetPredicate/ScalarOperator/ScalarExpressionList/ScalarOperator/MultipleAssign/Assign')
        as foo_col(info)
where foo_col.info.exist('./ColumnReference[@Table="[#foo]"]') = 1

递归部分使用依赖列搜索"DefinedValue"节点,并提取列表达式中使用的所有"ColumnReference"和"Const"子节点.XML到SQL的转换过于复杂.

union all    
select
    (select internal_col.info.query('.') for xml raw('shp:root') ,type)
  , source_info.column_info
  , source_info.const_info
  , prev_dependencies.iteration_no + 1
from @xml_plan.nodes('//DefinedValue/ColumnReference') as internal_col(info)
  inner join cte_column_dependencies as prev_dependencies -- Filters by depended columns.
        on prev_dependencies.source_column_info.value('(//ColumnReference/@Column)[1]' ,'nvarchar(4000)') = internal_col.info.value('(./@Column)[1]' ,'nvarchar(4000)')
        and exists (select prev_dependencies.source_column_info.value('(.//@Schema)[1]'   ,'nvarchar(4000)') intersect select internal_col.info.value('(./@Schema)[1]'   ,'nvarchar(4000)'))
        and exists (select prev_dependencies.source_column_info.value('(.//@Database)[1]' ,'nvarchar(4000)') intersect select internal_col.info.value('(./@Database)[1]' ,'nvarchar(4000)'))
        and exists (select prev_dependencies.source_column_info.value('(.//@Server)[1]'   ,'nvarchar(4000)') intersect select internal_col.info.value('(./@Server)[1]'   ,'nvarchar(4000)'))
  cross apply ( -- Becouse only column or only constant can be places in result row.
            select (select source_col.info.query('.') for xml raw('shp:root') ,type) as column_info
                 , null                                                              as const_info
              from internal_col.info.nodes('..//ColumnReference') as source_col(info)
            union all
            select null                                                         as column_info
                 , (select const.info.query('.') for xml raw('shp:root') ,type) as const_info
              from internal_col.info.nodes('..//Const') as const(info)
        ) as source_info
where source_info.column_info is null
    or (
        -- Except same node selected by '..//ColumnReference' from its sources. Sorry, I'm not so well to check it with XQuery simple.
            source_info.column_info.value('(//@Column)[1]' ,'nvarchar(4000)') <> internal_col.info.value('(./@Column)[1]' ,'nvarchar(4000)')
        and (select source_info.column_info.value('(//@Schema)[1]'   ,'nvarchar(4000)') intersect select internal_col.info.value('(./@Schema)[1]'   ,'nvarchar(4000)')) is null
        and (select source_info.column_info.value('(//@Database)[1]' ,'nvarchar(4000)') intersect select internal_col.info.value('(./@Database)[1]' ,'nvarchar(4000)')) is null
        and (select source_info.column_info.value('(//@Server)[1]'   ,'nvarchar(4000)') intersect select internal_col.info.value('(./@Server)[1]'   ,'nvarchar(4000)')) is null
      )
)

最后,它是将XML转换为适当的人类文本的select语句.

select
  --  col_dep.target_column_info
  --, col_dep.source_column_info
  --, col_dep.const_info
    coalesce(col_dep.target_column_info.value('(.//shp:ColumnReference/@Server)[1]'   ,'nvarchar(4000)') + '.' ,'')
  + coalesce(col_dep.target_column_info.value('(.//shp:ColumnReference/@Database)[1]' ,'nvarchar(4000)') + '.' ,'')
  + coalesce(col_dep.target_column_info.value('(.//shp:ColumnReference/@Schema)[1]'   ,'nvarchar(4000)') + '.' ,'')
  + col_dep.target_column_info.value('(.//shp:ColumnReference/@Column)[1]' ,'nvarchar(4000)')
    as target_column_name
  , coalesce(col_dep.source_column_info.value('(.//shp:ColumnReference/@Server)[1]'   ,'nvarchar(4000)') + '.' ,'')
  + coalesce(col_dep.source_column_info.value('(.//shp:ColumnReference/@Database)[1]' ,'nvarchar(4000)') + '.' ,'')
  + coalesce(col_dep.source_column_info.value('(.//shp:ColumnReference/@Schema)[1]'   ,'nvarchar(4000)') + '.' ,'')
  + col_dep.source_column_info.value('(.//shp:ColumnReference/@Column)[1]' ,'nvarchar(4000)')
    as source_column_name
  , col_dep.const_info.value('(/shp:root/shp:Const/@ConstValue)[1]' ,'nvarchar(4000)')
    as const_value
from cte_column_dependencies as col_dep
order by col_dep.iteration_no ,target_column_name ,source_column_name
option (maxrecursion 512) -- It's an assurance from infinite loop.