Question

我目前正在探索SQL服务器XML列和选择性索引以满足我们的需求。为此，我创建了一个名为Incidents的表，并创建了Selective Index和Secondary selective Indexes（下面的脚本）。

当我运行以下查询时，它确实使用了选择性索引，但查询计划对Severity列数据执行IS NOT NULL谓词，然后对其进行排序。当表中的数据很大时，这会显着降低查询的性能。我已经看到表中有400万行，完成后续查询需要大约20秒。

我在这里遗漏了什么？

select TOP 100 Data.value('(/Incident/Severity)[1]', 'int') AS Severity,

Data.value('(/Incident/OwningTenantId)[1]', 'VARCHAR(800)') AS OwningTenantId,

Data.value('(/Incident/OwningTeamId)[1]', 'NVARCHAR(800)') AS OwningTeamId

FROM Incidents

WHERE Data.value('(/Incident/Severity)[1]', 'int') = 1
ORDER BY Data.value('(/Incident/OwningTenantId)[1]', 'NVARCHAR(800)')

指数：

CREATE TABLE [dbo].[Incidents](
    [id] [uniqueidentifier] NOT NULL,
    [Data] [xml] NOT NULL,
 CONSTRAINT [PK_Incidents] PRIMARY KEY CLUSTERED 
(
    [id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

GO

CREATE SELECTIVE XML INDEX sxi_Incident_Data ON Incidents(Data)
 FOR 
 (
 Severity = '/Incident/Severity' AS SQL int SINGLETON,
 OwningTeamId = '/Incident/OwningTeamId' AS SQL NVARCHAR(400) SINGLETON,
 OwningTenantId = '/Incident/OwningTenantId' AS SQL NVARCHAR(400) SINGLETON,
 id = '/Incident/_id' AS SQL BIGINT SINGLETON
 )

 GO

 create xml index sxi_secondary_severity on Incidents(Data)
 using xml index sxi_Incident_Data
 for (Severity);

 GO

 create xml index sxi_secondary_OwningTeamId on Incidents(Data)
 using xml index sxi_Incident_Data
 for (OwningTeamId); 

 GO

 create xml index sxi_secondary_OwningTenantId on Incidents(Data)
 using xml index sxi_Incident_Data
 for (OwningTenantId); 

 GO


 create xml index sxi_secondary_Id on Incidents(Data)
 using xml index sxi_Incident_Data
 for (id); 

 GO

示例XML：

<Incident>
  <_id>123</_id>
  <Severity>3</Severity>
  <IncidentStatus>RESOLVED</IncidentStatus>
  <CreateDate>2014-05-04 05:43:58.317</CreateDate>
  <LastUpdateDate>2014-05-06 18:47:39.037</LastUpdateDate>
  <AlertSourceLocalId>20070</AlertSourceLocalId>
  <SourceIncidentId>35d0bfe4-ccb9-491f-a30c-ea7685ffe8c0</SourceIncidentId>
  <SourceCreateDate>2014-05-04 02:51:14.000</SourceCreateDate>
  <SourceCreatedBy>Someone</SourceCreatedBy>
  <SourceModifiedDate>2014-05-04 05:43:57.797</SourceModifiedDate>
  <SourceOrigin>Some Origin</SourceOrigin>
  <CorrelationId>correlatioid</CorrelationId>
  <RoutingId>Route123</RoutingId>
  <Datacenter>Unknown</Datacenter>
  <Environment>INT</Environment>
  <DeviceGroup>Devicegroup</DeviceGroup>
  <DeviceName>DeviceName</DeviceName>
  <RaisingEnvironment>PROD</RaisingEnvironment>
  <RaisingDatacenter>Unknown</RaisingDatacenter>
  <RaisingDeviceGroup>DEviceGroup</RaisingDeviceGroup>
  <RaisingDeviceName>FakeDevice</RaisingDeviceName>
  <PrimaryIncidentId>1234</PrimaryIncidentId>
  <RelatedLinksCount>0</RelatedLinksCount>
  <ExternalLinksCount>0</ExternalLinksCount>
  <HitCount>0</HitCount>
  <ChildCount>0</ChildCount>
  <Title>Some Title</Title>
  <ReproSteps>&#x0;</ReproSteps>
  <OwningTenantId>564</OwningTenantId>
  <OwningTeamId>123</OwningTeamId>
  <ResolveDate>2014-05-06 18:47:39.037</ResolveDate>
  <ResolvedBy>SomeOne</ResolvedBy>
  <MitigateDate>2014-05-06 18:45:55.403</MitigateDate>
  <MitigatedBy>Someone</MitigatedBy>
  <Mitigation>N/A</Mitigation>
  <IsNoise>0</IsNoise>
  <IsSecurityRisk>0</IsSecurityRisk>
  <IsCustomerImpacting>0</IsCustomerImpacting>
  <OriginatingTenantId>10066</OriginatingTenantId>
  <ImpactStartDate>2014-05-01 23:31:22.000</ImpactStartDate>
  <RootCauseNeedsInvestigation>0</RootCauseNeedsInvestigation>
  <ConnectorTenantId>10066</ConnectorTenantId>
  <RelationshipId>1852546</RelationshipId>
  <SuppressAutoUpdate>0</SuppressAutoUpdate>
</Incident>

摄制：创建表索引

-- Create Table 
IF(EXISTS(SELECT * FROM sys.tables WHERE [Name] = 'XmlTable' AND [Type] = 'U'))
BEGIN
    DROP TABLE XmlTable
END

CREATE TABLE [dbo].[XmlTable](
    [id] [uniqueidentifier] NOT NULL,
    [Data] [xml] NULL
PRIMARY KEY CLUSTERED 
(
    [id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

GO

-- Populate Data
DECLARE @i INT  = 0
DECLARE @XML NVARCHAR(MAX), 
        @Severity INT, 
        @OwningTeamId VARCHAR(400), 
        @OwningTenantId VARCHAR(400), 
        @IncidentStatus varchar(100),
        @Mod SMALLINT
WHILE @i < 500
BEGIN   
    SET @i = @i + 1
    SET @Mod = @i % 3

    SELECT @Severity = @Mod + 1,
           @OwningTeamId = 'OwningTeam' + CAST(@Mod AS VARCHAR),    
           @OwningTenantId = 'OwningTenantId' + CAST(@Mod AS VARCHAR),
           @IncidentStatus = CASE @Mod 
                                WHEN 0 THEN 'Active' 
                                WHEN 1 THEN 'Resolved' 
                                WHEN 2 THEN 'Closed' 
                             END    
    SET @XML = 
    '<Incident>' +
        '<_id>' + CAST(@i AS VARCHAR) + '</_id>' +
        '<Severity>' + CAST(@Severity AS VARCHAR) + '</Severity>' +
        '<OwningTeamId>' + @OwningTeamId + '</OwningTeamId>' +
        '<OwningTenantId>' + @OwningTenantId + '</OwningTenantId>' +
        '<IncidentStatus>' + @IncidentStatus + '</IncidentStatus>' +
    '</Incident>'
    INSERT INTO XmlTable
    SELECT NEWID(), @XML
END


-- Creat Indices
CREATE SELECTIVE XML INDEX [sxi_Data] ON [dbo].[XmlTable]
(
    [Data]
)
FOR
(
[Severity] = '/Incident/Severity' as SQL [int] SINGLETON , 
[OwningTeamId] = '/Incident/OwningTeamId' as SQL [nvarchar](400) SINGLETON , 
[OwningTenantId] = '/Incident/OwningTenantId' as SQL [nvarchar](400) SINGLETON , 
[id] = '/Incident/_id' as SQL [bigint] SINGLETON , 
[TicketStatus] = '/Incident/IncidentStatus' as SQL [nvarchar](100) SINGLETON 
)
WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON)
GO

CREATE XML INDEX [sxi_secondary_Id] ON [dbo].[XmlTable]
(
    [Data]
)USING XML INDEX [sxi_Data] FOR (
[id]
) 
WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON)
GO

CREATE XML INDEX [sxi_secondary_OwningTeamId] ON [dbo].[XmlTable]
(
    [Data]
)USING XML INDEX [sxi_Data] FOR (
[OwningTeamId]
) 
WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON)
GO

USE [XMLDocuemntStore]
GO


CREATE XML INDEX [sxi_secondary_OwningTenantId] ON [dbo].[XmlTable]
(
    [Data]
)USING XML INDEX [sxi_Data] FOR (
[OwningTenantId]
) 
WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON)
GO

USE [XMLDocuemntStore]
GO


CREATE XML INDEX [sxi_secondary_severity] ON [dbo].[XmlTable]
(
    [Data]
)USING XML INDEX [sxi_Data] FOR (
[Severity]
) 
WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON)
GO

示例查询：检查右侧的查询计划。

select TOP 100 Data.value('(/Incident/Severity)[1]', 'int') AS Severity
FROM XmlTable
WHERE Data.value('(/Incident/Severity)[1]', 'int') = 1
ORDER BY Data.value('(/Incident/OwningTenantId)[1]', 'NVARCHAR(800)')

Answer 1

由于XPATH查询中的[1]，需要SORT TOP N.要摆脱这种情况，您需要确保SQL Server所需的xml元素仅在事件元素中出现一次。为此，您需要使用XSD文档强烈键入XML。你可以这样创建一个：

CREATE XML SCHEMA COLLECTION Incident_XSD AS
N'<?xml version="1.0" encoding="UTF-16"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="Incident">
    <xs:complexType>
      <xs:sequence>
        <xs:element type="xs:int" name="_id" />
        <xs:element type="xs:int" name="Severity" />
        <xs:element type="xs:string" name="OwningTeamId" />
        <xs:element type="xs:string" name="OwningTenantId" />
        <xs:element type="xs:string" name="IncidentStatus"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>' ;
GO

在表定义中使用它，如此

[Data] [xml](Incident_XSD) NULL

现在以下查询有效

select TOP 100 Data.value('/Incident[1]/Severity', 'int') AS Severity
FROM XmlTable
WHERE Data.value('/Incident[1]/Severity', 'int') = 1
ORDER BY Data.value('/Incident[1]/OwningTenantId', 'NVARCHAR(800)')

在一秒钟内返回，或在表格中以毫秒行返回。

PS：您可能想重新考虑使用GUID作为主键

选择性XML索引查询计划

1 个答案: