查询时出现死锁INFORMATION_SCHEMA

Question

我有一个进程根据发布的元数据层中的更改动态更改我的SQL2K5表结构。

例如，如果一个新的列需要添加和表没有依赖关系 - 步骤是： 1.使用T-SQL对于任何索引&已经在表中存在主键[这些创建脚本脚本包括下面] 2.删除该表 3.重新创建从具有新列的元层的表 4.执行在步骤＃1中 5.创建的脚本使用BulkCopy

填充表

以上是通过.NET程序集启动的，每天在3个并发流中运行。

我在步骤1中收到死锁错误 - 当我访问INFORMATION_SCHEMA表格来编制索引/键时。我在这些脚本中使用了提示WITH（NOLOCK），认为这应该可以防止3个这样的操作并发运行时发生任何锁定。一个表只能在1个流中处理（创建或脚本）。

还有什么我需要做的吗？

任何意见非常感谢。

[脚本]

ALTER Procedure [dbo].[s$spScriptPrimaryKeyForTable] 
@Tablename varchar(100) 
AS 


-- Get all existing primary keys 
DECLARE cPK CURSOR FOR 
SELECT TABLE_NAME, CONSTRAINT_NAME 
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WITH(NOLOCK) 
WHERE upper(TABLE_NAME)=upper(@Tablename) 
ORDER BY TABLE_NAME 

DECLARE @PkTable SYSNAME 
DECLARE @PkName SYSNAME 

-- Loop through all the primary keys 
OPEN cPK 
FETCH NEXT FROM cPK INTO @PkTable, @PkName 
WHILE (@@FETCH_STATUS = 0) 
BEGIN 
DECLARE @PKSQL NVARCHAR(4000) SET @PKSQL = '' 
SET @PKSQL = 'ALTER TABLE ' + @PkTable + ' ADD CONSTRAINT ' + @PkName + ' PRIMARY KEY CLUSTERED (' 

-- Get all columns for the current primary key 
DECLARE cPKColumn CURSOR FOR 
SELECT COLUMN_NAME 
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE WITH(NOLOCK) 
WHERE TABLE_NAME = @PkTable AND CONSTRAINT_NAME = @PkName 
ORDER BY ORDINAL_POSITION 
OPEN cPKColumn 

DECLARE @PkColumn SYSNAME 
DECLARE @PkFirstColumn BIT SET @PkFirstColumn = 1 
-- Loop through all columns and append the sql statement 
FETCH NEXT FROM cPKColumn INTO @PkColumn 
WHILE (@@FETCH_STATUS = 0) 
BEGIN 
IF (@PkFirstColumn = 1) 
SET @PkFirstColumn = 0 
ELSE 
SET @PKSQL = @PKSQL + ', ' 

SET @PKSQL = @PKSQL + @PkColumn 

FETCH NEXT FROM cPKColumn INTO @PkColumn 
END 
CLOSE cPKColumn 
DEALLOCATE cPKColumn 

SET @PKSQL = @PKSQL + ')' 
-- Print the primary key statement 
-- PRINT @PKSQL 

FETCH NEXT FROM cPK INTO @PkTable, @PkName 
END 
CLOSE cPK 
DEALLOCATE cPK 


SELECT ISNULL(@PKSQL,' ') 

================ 

ALTER Procedure [dbo].[s$spScriptIndexesForTable] 
@Tablename varchar(100) 

AS 

DECLARE @RetVal varchar(4000) 
SET @RetVal = '' 

-- Get all existing indexes, but NOT the primary keys 
DECLARE cIX CURSOR FOR 
SELECT OBJECT_NAME(SI.Object_ID), SI.Object_ID, SI.Name, SI.Index_ID 
FROM Sys.Indexes SI WITH(NOLOCK) 
LEFT JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC WITH(NOLOCK) ON SI.Name = TC.CONSTRAINT_NAME AND OBJECT_NAME(SI.Object_ID) = TC.TABLE_NAME 
WHERE TC.CONSTRAINT_NAME IS NULL 
AND OBJECTPROPERTY(SI.Object_ID, 'IsUserTable') = 1 
AND upper(OBJECT_NAME(SI.Object_ID))=upper(@Tablename) 
ORDER BY OBJECT_NAME(SI.Object_ID), SI.Index_ID 

DECLARE @IxTable SYSNAME 
DECLARE @IxTableID INT 
DECLARE @IxName SYSNAME 
DECLARE @IxID INT 

-- Loop through all indexes 
OPEN cIX 
FETCH NEXT FROM cIX INTO @IxTable, @IxTableID, @IxName, @IxID 
WHILE (@@FETCH_STATUS = 0) 
BEGIN 
DECLARE @IXSQL NVARCHAR(4000) 
--SET @PKSQL = '' 
SET @IXSQL = 'CREATE ' 

-- Check if the index is unique 
IF (INDEXPROPERTY(@IxTableID, @IxName, 'IsUnique') = 1) 
SET @IXSQL = @IXSQL + 'UNIQUE ' 
-- Check if the index is clustered 
IF (INDEXPROPERTY(@IxTableID, @IxName, 'IsClustered') = 1) 
SET @IXSQL = @IXSQL + 'CLUSTERED ' 

SET @IXSQL = @IXSQL + 'INDEX ' + @IxName + ' ON [' + @IxTable + '] (' 

-- Get all columns of the index 
DECLARE cIxColumn CURSOR FOR 
SELECT SC.Name,IC.[is_included_column],IC.is_descending_key 
FROM Sys.Index_Columns IC WITH(NOLOCK) 
JOIN Sys.Columns SC WITH(NOLOCK) ON IC.Object_ID = SC.Object_ID AND IC.Column_ID = SC.Column_ID 
WHERE IC.Object_ID = @IxTableID AND Index_ID = @IxID 
ORDER BY IC.Index_Column_ID,IC.is_included_column 

DECLARE @IxColumn SYSNAME 
DECLARE @IxIncl bit 
DECLARE @Desc bit 
DECLARE @IxIsIncl bit set @IxIsIncl = 0 
DECLARE @IxFirstColumn BIT SET @IxFirstColumn = 1 

-- Loop throug all columns of the index and append them to the CREATE statement 
OPEN cIxColumn 
FETCH NEXT FROM cIxColumn INTO @IxColumn, @IxIncl, @Desc 
WHILE (@@FETCH_STATUS = 0) 
BEGIN 

IF (@IxFirstColumn = 1) 
BEGIN 
SET @IxFirstColumn = 0 
END 
ELSE 
BEGIN 
--check to see if it's an included column 
IF ((@IxIsIncl = 0) AND (@IxIncl = 1)) 
BEGIN 
SET @IxIsIncl = 1 
SET @IXSQL = @IXSQL + ') INCLUDE (' 
END 
ELSE 
BEGIN 
SET @IXSQL = @IXSQL + ', ' 
END 
END 

SET @IXSQL = @IXSQL + '[' + @IxColumn + ']' 
--check to see if it's DESC 
IF @Desc = 1 
SET @IXSQL = @IXSQL + ' DESC' 

FETCH NEXT FROM cIxColumn INTO @IxColumn, @IxIncl, @Desc 
END 
CLOSE cIxColumn 
DEALLOCATE cIxColumn 

SET @IXSQL = @IXSQL + ')' 

-- Print out the CREATE statement for the index 
--SELECT 'IXSQL: ' + @IXSQL 
IF @RetVal IS NULL 
SET @RetVal = '' 
--SELECT 'Retval: ' + @RetVal 
SET @RetVal = @RetVal + @IXSQL + ' ' 

FETCH NEXT FROM cIX INTO @IxTable, @IxTableID, @IxName, @IxID 
END 

CLOSE cIX 
DEALLOCATE cIX 

SELECT ISNULL(@RetVal,' ') 

Answer 1

1. INFORMATION_SCHEMA的意见是 - 观点。您无法更新它们，因此它们不太可能导致任何死锁。如果你想确定真正的源代码（我认为这与你的修改有关，或者你没有显示的游标中的其他代码，或者你调用这些程序时调用的其他代码 - 因为选择意见然后选择变量不能成为原因），我建议阅读Gail Shaw's blog post on interpreting deadlocks。

2. 尽管（1）我仍然建议使用比INFORMATION_SCHEMA更现代的目录视图。例如，可以从sys.key_constraints中派生出相同的信息。

3. 您正在使用默认光标选项;你在嵌套游标。如果最终仍然使用游标，则应该习惯于使用资源较少的游标（例如LOCAL STATIC FORWARD_ONLY READ_ONLY）。

4. 实际上您并不需要光标来执行此操作。下面是我会重新写的PK表脚本：

   CREATE PROCEDURE dbo.ScriptPKForTable 
       @TableName SYSNAME 
   AS 
   BEGIN 
       SET NOCOUNT ON; 
   
       DECLARE 
        @pkName SYSNAME, 
        @clustered BIT, 
        @object_id INT, 
        @sql  NVARCHAR(MAX); 
   
       SELECT 
        @object_id = OBJECT_ID(UPPER(@TableName)); 
   
       SELECT 
        @pkName = kc.name, 
        @clustered = CASE i.[type] 
        WHEN 1 THEN 1 ELSE 0 END 
       FROM 
        sys.key_constraints AS kc 
       INNER JOIN 
        sys.indexes AS i 
        ON kc.parent_object_id = i.[object_id] 
        AND kc.unique_index_id = i.index_id 
       WHERE 
        kc.parent_object_id = @object_id 
        AND kc.[type] = 'pk'; 
   
       SET @sql = N'ALTER TABLE ' + QUOTENAME(@TableName) 
        + ' ADD CONSTRAINT ' + @pkName 
        + ' PRIMARY KEY ' + CASE @clustered 
        WHEN 1 THEN 'CLUSTERED' ELSE '' END + ' ('; 
   
       SELECT 
        @sql = @sql + c.name + ',' 
       FROM 
        sys.index_columns AS ic 
       INNER JOIN 
        sys.indexes AS i 
        ON ic.index_id = i.index_id 
        AND ic.[object_id] = i.[object_id] 
       INNER JOIN 
        sys.key_constraints AS kc 
        ON i.[object_id] = kc.[parent_object_id] 
        AND kc.unique_index_id = i.index_id 
       INNER JOIN 
        sys.columns AS c 
        ON i.[object_id] = c.[object_id] 
        AND ic.column_id = c.column_id 
       WHERE 
        kc.[type] = 'PK' 
        AND kc.parent_object_id = @object_id 
       ORDER BY key_ordinal; 
   
       SET @sql = LEFT(@sql, LEN(@sql) - 1) + ');'; 
   
       SELECT COALESCE(@sql, ' '); 
   END 
   GO 
   

至于索引创建脚本，我认为这是一个更好的办法没有明确的指针再做一次（，而不是避免光标是目标，但代码将成为一个LOT清理器）。首先，你从索引需要一个函数来建立的任一按键或包括列：

CREATE FUNCTION dbo.BuildIndexColumns 
(
    @object_id  INT, 
    @index_id   INT, 
    @included_columns BIT 
) 
RETURNS NVARCHAR(MAX) 
AS 
BEGIN 
    DECLARE @s NVARCHAR(MAX); 

    SELECT @s = N''; 

    SELECT @s = @s + c.name + CASE ic.is_descending_key 
    WHEN 1 THEN ' DESC' ELSE '' END + ',' 
    FROM sys.index_columns AS ic 
    INNER JOIN sys.columns AS c 
    ON ic.[object_id] = c.[object_id] 
    AND ic.column_id = c.column_id 
    WHERE c.[object_id] = @object_id 
    AND ic.[object_id] = @object_id 
    AND ic.index_id = @index_id 
    AND ic.is_included_column = @included_columns 
    ORDER BY ic.key_ordinal; 

    IF @s > N'' 
    SET @s = LEFT(@s, LEN(@s)-1); 

    RETURN (NULLIF(@s, N'')); 
END 
GO 

有了这一功能，ScriptIndexes过程是很容易的：

CREATE PROCEDURE dbo.ScriptIndexesForTable 
    @TableName SYSNAME 
AS 
BEGIN 
    SET NOCOUNT ON; 

    DECLARE 
     @sql  NVARCHAR(MAX), 
     @object_id INT; 

    SELECT @sql = N'', @object_id = OBJECT_ID(UPPER(@TableName)); 

    SELECT @sql = @sql + 'CREATE ' 
     + CASE i.is_unique WHEN 1 THEN 'UNIQUE ' ELSE '' END 
     + CASE i.[type] WHEN 1 THEN 'CLUSTERED ' ELSE '' END 
     + ' INDEX ' + i.name + ' ON ' + QUOTENAME(@TableName) + ' (' 
     + dbo.BuildIndexColumns(@object_id, i.index_id, 0) 
     + ')' + COALESCE(' INCLUDE(' 
     + dbo.BuildIndexColumns(@object_id, i.index_id, 1) 
     + ')', '') + ';' + CHAR(13) + CHAR(10) 
    FROM 
     sys.indexes AS i 
    WHERE 
     i.[object_id] = @object_id 
     -- since this will be covered by ScriptPKForTable: 
     AND i.is_primary_key = 0 
    ORDER BY i.index_id; 

    SELECT COALESCE(@sql, ' '); 
END 
GO 

请注意，我的解决方案不承担PK是聚集的（你的PK脚本是硬编码的群集，但是你的索引脚本假设任何索引都可以聚集）。我还忽略了其他属性，例如文件组，分区或筛选索引（2005年不支持）。