我需要向CDC添加几列以获取已经被跟踪的表。我的方法如下:
EXEC sys.sp_cdc_drop_job 'capture'
BEGIN TRANSACTION
BEGIN TRY
-- Copy existing data of the tracked table into a temporary table
SELECT * INTO CDC.dbo_MyTable_Temp FROM CDC.dbo_MyTable_CT
-- Add the new column to the temp table. This allows us to just use INSERT..SELECT * later
ALTER TABLE CDC.dbo_MyTable_Temp ADD MyColumn INT NULL
-- Disable CDC for the source table temporarily. This will drop the CDC table
EXEC sys.sp_cdc_disable_table @source_schema = 'dbo', @source_name = 'MyTable', @capture_instance = 'dbo_MyTable'
-- Reenable CDC for the source table. This will recreate the table with the new columns
EXEC sys.sp_cdc_enable_table @source_schema = 'dbo', @source_name = 'MyTable', @capture_instance = 'dbo_MyTable', @supports_net_changes = 1, @role_name = NULL, @filegroup_name = 'CDCGROUP'
-- Insert the old values into the CDC table
INSERT INTO cdc.dbo_MyTable_CT SELECT * FROM cdc.dbo_MyTable_Temp
-- Correct the start_lsn in CDC.change_tables. Otherwise all of the CDC stored procedures will be confused
-- and although the old data will exist in the table the functions won't return it
UPDATE cdc.change_tables SET start_lsn = (SELECT MIN(__$start_lsn) FROM cdc.dbo_MyTable_Temp) WHERE capture_instance = 'dbo_MyTable'
-- Drop the temp table
DROP TABLE cdc.dbo_MyTable_Temp
COMMIT TRANSACTION
END TRY
BEGIN CATCH
ROLLBACK TRANSACTION
RAISERROR('Error!', 16, 1)
END CATCH
EXEC sys.sp_cdc_add_job 'capture'
但是,当作业在重新添加后再次运行时,会生成错误,指出CDC.lsn_time_mapping
上存在违反主键约束的错误。
有什么建议吗?
谢谢!
答案 0 :(得分:0)
我无法找到错误的确切原因,因为lsn_time_mapping
的更新发生在扩展存储过程中,但我能够使用不同的代码来添加列。基本上,我坚持使用CDC存储过程而不是在CDC表上执行ALTER TABLE
命令。代码如下:
-- Create a new capture instance for the table
EXEC sys.sp_cdc_enable_table @source_schema = 'dbo', @source_name = 'MyTable', @capture_instance = 'dbo_MyTable_New', @supports_net_changes = 1, @role_name = NULL, @filegroup_name = 'CDCGROUP'
-- Copy all of the existing data from the old capture instance
INSERT INTO CDC.dbo_MyTable_New_CT SELECT *, NULL AS NewColumn1, NULL AS NewColumn2 FROM CDC.dbo_MyTable_CT
-- Disable the old capture instance
EXEC sys.sp_cdc_disable_table @source_schema = 'dbo', @source_name = 'MyTable', @capture_instance = 'dbo_MyTable'
-- Now we need to jump through some hoops to rename the capture instance back to what it was:
-- Recreate a new capture instance with the old name again
EXEC sys.sp_cdc_enable_table @source_schema = 'dbo', @source_name = 'MyTable', @capture_instance = 'dbo_MyTable', @supports_net_changes = 1, @role_name = NULL, @filegroup_name = 'CDCGROUP'
-- Copy all of the data over again
INSERT INTO CDC.dbo_MyTable_CT SELECT * FROM CDC.dbo_MyTable_New_CT
-- Remove the capture instance that we had been using to add the new columns
EXEC sys.sp_cdc_disable_table @source_schema = 'dbo', @source_name = 'MyTable', @capture_instance = 'dbo_MyTable_New'
-- We need to correct the start_lsn in the cdc.change_tables table. Otherwise all of the CDC stored procedures and views will be confused and
-- although the old data will exist in the CDC table it wouldn't be returned by those CDC procs
UPDATE cdc.change_tables SET start_lsn = (SELECT MIN(__$start_lsn) FROM cdc.dbo_MyTable_CT) WHERE capture_instance = 'dbo_MyTable'
请注意,我在数据库停机期间执行此操作。如果在使用数据库时需要执行此操作,则可能需要在insert语句中添加WHERE
子句,以便不将同一记录从一个表复制到已存在的表中。当两个捕获实例都处于活动状态时,任何影响表的DML都将将行放入两个捕获实例中。