Question

我对光标不是很熟悉，但是我只需要了解一件相对简单的事情。看一下下面脚本的结构，并注意实例化光标的位置以及关闭/取消分配光标的位置。如果脚本在我编写的/* most of the code here */处死锁并且事务被回滚，然后重新尝试，那么脚本尝试进行fetch next时会发生什么？由于执行从未达到close / deallocate游标行，因此我觉得在第二次尝试时游标将获取第二行。请注意，我并不是在声称它写得正确-我觉得我遇到的问题是由于在提交事务之后将游标释放了。

declare LPCursor cursor for 
/*
...
*/

while (@deadlockretries <= @Maxlockretries)
begin

  begin try
    begin transaction

      fetch next from LPCursor into @var1, @var2, @var3
      while (@@fetch_status = 0)
      begin

        /* most of the code here */

      end 

    commit transaction

    close LPCursor
    deallocate LPCursor

  end try

  begin catch

    if (error_number() = 1205)
    begin

      if xact_state() <> 0 
      begin

        rollback transaction

      end

    end

  end catch

end

Answer 1

它将获取下一个，但是我想您知道以这种方式执行操作时，您会丢失一个“处理”块，因为您将其回滚到了中间。无论哪种方式，都需要修改您的代码以向您展示代码的前进方向：

CREATE TABLE #tmp(VAL1 varchar(10), VAL2 varchar(10), VAL3 varchar(10))
INSERT INTO #tmp VALUES('val1_1','val1_2','val1_3')
INSERT INTO #tmp VALUES('val2_1','val2_2','val2_3')
INSERT INTO #tmp VALUES('val3_1','val3_2','val3_3')
INSERT INTO #tmp VALUES('val4_1','val4_2','val4_3')
INSERT INTO #tmp VALUES('val5_1','val5_2','val5_3')
INSERT INTO #tmp VALUES('val6_1','val6_2','val6_3')
INSERT INTO #tmp VALUES('val7_1','val7_2','val7_3')


DECLARE @deadlockretries int = 0
declare @Maxlockretries int = 3

declare @var1 varchar(10)
declare @var2 varchar(10)
declare @var3 varchar(10)

DECLARE LPCursor cursor for SELECT VAL1, val2, val3 from #tmp
open LPCursor
while (@deadlockretries <= @Maxlockretries)
begin
    PRINT 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'

  begin try
    begin transaction

      fetch next from LPCursor into @var1, @var2, @var3
      -- print @var1 + @var2 + @var3
      while (@@fetch_status = 0)
      begin
      print @var1 + @var2 + @var3
        /* most of the code here */
        select 1/0
        fetch next from LPCursor into @var1, @var2, @var3
    end 

    commit transaction
    SET @deadlockretries = @Maxlockretries
    close LPCursor
    deallocate LPCursor

  end try

  begin catch
  PRINT 'ERROR'
  print error_number()
    if (error_number() = 8134)
    begin

      if xact_state() <> 0 
      begin
      PRINT 'ROLLBACK'
        rollback transaction
      end
    end
  end catch
  PRINT 'END'
  SET @deadlockretries += 1
end

IF CURSOR_STATUS('global','LPCursor')>=-1
BEGIN
 DEALLOCATE LPCursor
END

如果根据此脚本设置回滚了交易，脚本是否会获取光标中的下一项？

1 个答案: