[英]Entity Framework Code First Fluent Api: Adding Indexes to columns
我正在运行 EF 4.2 CF 并希望在我的 POCO 对象中的某些列上创建索引。
举个例子,假设我们有这个员工类:
public class Employee
{
public int EmployeeID { get; set; }
public string EmployeeCode { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime HireDate { get; set; }
}
我们经常通过员工的 EmployeeCode 搜索员工,因为有很多员工,出于性能原因将其编入索引会很好。
我们可以用 fluent api 以某种方式做到这一点吗? 或者数据注释?
我知道可以执行这样的 sql 命令:
context.Database.ExecuteSqlCommand("CREATE INDEX IX_NAME ON ...");
我非常想避免这样的原始 SQL。
我知道这不存在,但正在寻找这些方面的东西:
class EmployeeConfiguration : EntityTypeConfiguration<Employee>
{
internal EmployeeConfiguration()
{
this.HasIndex(e => e.EmployeeCode)
.HasIndex(e => e.FirstName)
.HasIndex(e => e.LastName);
}
}
或者可能使用System.ComponentModel.DataAnnotations
POCO 可能看起来像这样(我再次知道这不存在):
public class Employee
{
public int EmployeeID { get; set; }
[Indexed]
public string EmployeeCode { get; set; }
[Indexed]
public string FirstName { get; set; }
[Indexed]
public string LastName { get; set; }
public DateTime HireDate { get; set; }
}
任何人都对如何做到这一点有任何想法,或者是否有任何计划实施一种方法来做到这一点,代码优先的方式?
更新:正如 Robba 在回答中提到的,此功能在 EF 6.1 版中实现
在 EF 4.3 中引入迁移后,您现在可以在修改或创建表时添加索引。 这是 ADO.NET 团队博客中EF 4.3 基于代码的迁移演练的摘录
namespace MigrationsCodeDemo.Migrations
{
using System.Data.Entity.Migrations;
public partial class AddPostClass : DbMigration
{
public override void Up()
{
CreateTable(
"Posts",
c => new
{
PostId = c.Int(nullable: false, identity: true),
Title = c.String(maxLength: 200),
Content = c.String(),
BlogId = c.Int(nullable: false),
})
.PrimaryKey(t => t.PostId)
.ForeignKey("Blogs", t => t.BlogId, cascadeDelete: true)
.Index(t => t.BlogId)
.Index(p => p.Title, unique: true);
AddColumn("Blogs", "Rating", c => c.Int(nullable: false, defaultValue: 3));
}
public override void Down()
{
DropIndex("Posts", new[] { "BlogId" });
DropForeignKey("Posts", "BlogId", "Blogs");
DropColumn("Blogs", "Rating");
DropTable("Posts");
}
}
}
这是添加索引的一种很好的强类型方式,这是我第一次发布问题时所寻找的。
您可以创建一个名为 indexed (如您所建议的)的属性,然后在自定义初始值设定项中选取该属性。
我创建了以下属性:
[AttributeUsage(AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
public class IndexAttribute : Attribute
{
public IndexAttribute(bool isUnique = false, bool isClustered = false, SortOrder sortOrder = SortOrder.Ascending)
{
IsUnique = isUnique;
IsClustered = isClustered;
SortOrder = sortOrder == SortOrder.Unspecified ? SortOrder.Ascending : sortOrder;
}
public bool IsUnique { get; private set; }
public bool IsClustered { get; private set; }
public SortOrder SortOrder { get; private set; }
//public string Where { get; private set; }
}
然后我创建了一个自定义初始值设定项,它获得了为我的上下文中的实体创建的表名列表。 我有两个基类,我的所有实体都继承了它们,因此我执行了以下操作来获取表名:
var baseEF = typeof (BaseEFEntity);
var baseLink = typeof (BaseLinkTable);
var types =
AppDomain.CurrentDomain.GetAssemblies().ToList().SelectMany(s => s.GetTypes()).Where(
baseEF.IsAssignableFrom).Union(AppDomain.CurrentDomain.GetAssemblies().ToList().SelectMany(
s => s.GetTypes()).Where(
baseLink.IsAssignableFrom));
var sqlScript = context.ObjectContext.CreateDatabaseScript();
foreach (var type in types)
{
var table = (TableAttribute) type.GetCustomAttributes(typeof (TableAttribute), true).FirstOrDefault();
var tableName = (table != null ? table.Name : null) ?? Pluralizer.Pluralize(type.Name);
然后我找到了每个实体上具有该属性的所有属性,然后执行 SQL 命令来生成每个属性的索引。 甜的!
//Check that a table exists
if (sqlScript.ToLower().Contains(string.Format(CREATETABLELOOKUP, tableName.ToLower())))
{
//indexes
var indexAttrib = typeof (IndexAttribute);
properties = type.GetProperties().Where(prop => Attribute.IsDefined(prop, indexAttrib));
foreach (var property in properties)
{
var attributes = property.GetCustomAttributes(indexAttrib, true).ToList();
foreach (IndexAttribute index in attributes)
{
var indexName = string.Format(INDEXNAMEFORMAT, tableName, property.Name,
attributes.Count > 1
? UNDERSCORE + (attributes.IndexOf(index) + 1)
: string.Empty);
try
{
context.ObjectContext.ExecuteStoreCommand(
string.Format(INDEX_STRING, indexName,
tableName,
property.Name,
index.IsUnique ? UNIQUE : string.Empty,
index.IsClustered ? CLUSTERED : NONCLUSTERED,
index.SortOrder == SortOrder.Ascending ? ASC : DESC));
}
catch (Exception)
{
}
}
}
我什至继续以相同的方式添加基于类的索引(可能有多个列)、唯一约束和默认约束。 真正好的一点是,如果您将这些属性放在继承的类上,索引或约束将应用于继承它的所有类(表)。
顺便说一句,复数助手包含以下内容:
public static class Pluralizer
{
private static object _pluralizer;
private static MethodInfo _pluralizationMethod;
public static string Pluralize(string word)
{
CreatePluralizer();
return (string) _pluralizationMethod.Invoke(_pluralizer, new object[] {word});
}
public static void CreatePluralizer()
{
if (_pluralizer == null)
{
var aseembly = typeof (DbContext).Assembly;
var type =
aseembly.GetType(
"System.Data.Entity.ModelConfiguration.Design.PluralizationServices.EnglishPluralizationService");
_pluralizer = Activator.CreateInstance(type, true);
_pluralizationMethod = _pluralizer.GetType().GetMethod("Pluralize");
}
}
}
要建立在frozen 的响应之上,您可以自己将其编码到迁移中。
首先,转到包管理器控制台并使用add-migration
创建一个新add-migration
,然后为其命名。 将出现空白迁移。 坚持这个:
public override void Up()
{
CreateIndex("TableName", "ColumnName");
}
public override void Down()
{
DropIndex("TableName",new[] {"ColumnName"});
}
请注意,如果您使用的是字符串字段,它也需要限制为 450 个字符的长度。
我最近也研究了这个并没有发现其他方法,所以我在为数据库做种时创建索引:
public class MyDBInitializer : DropCreateDatabaseIfModelChanges<MyContext>
{
private MyContext _Context;
protected override void Seed(MyContext context)
{
base.Seed(context);
_Context = context;
// We create database indexes
CreateIndex("FieldName", typeof(ClassName));
context.SaveChanges();
}
private void CreateIndex(string field, Type table)
{
_Context.Database.ExecuteSqlCommand(String.Format("CREATE INDEX IX_{0} ON {1} ({0})", field, table.Name));
}
}
请注意,在 Entity Framework 6.1(目前处于测试阶段)中,将支持 IndexAttribute 来注释索引属性,这将在您的 Code First 迁移中自动生成(唯一)索引。
好吧,我在网上找到了一个解决方案并对其进行了调整以满足我的需求,它是:
[AttributeUsage(AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
public class IndexAttribute : Attribute
{
public IndexAttribute(string name, bool unique = false)
{
this.Name = name;
this.IsUnique = unique;
}
public string Name { get; private set; }
public bool IsUnique { get; private set; }
}
public class IndexInitializer<T> : IDatabaseInitializer<T> where T : DbContext
{
private const string CreateIndexQueryTemplate = "CREATE {unique} INDEX {indexName} ON {tableName} ({columnName});";
public void InitializeDatabase(T context)
{
const BindingFlags PublicInstance = BindingFlags.Public | BindingFlags.Instance;
Dictionary<IndexAttribute, List<string>> indexes = new Dictionary<IndexAttribute, List<string>>();
string query = string.Empty;
foreach (var dataSetProperty in typeof(T).GetProperties(PublicInstance).Where(p => p.PropertyType.Name == typeof(DbSet<>).Name))
{
var entityType = dataSetProperty.PropertyType.GetGenericArguments().Single();
TableAttribute[] tableAttributes = (TableAttribute[])entityType.GetCustomAttributes(typeof(TableAttribute), false);
indexes.Clear();
string tableName = tableAttributes.Length != 0 ? tableAttributes[0].Name : dataSetProperty.Name;
foreach (PropertyInfo property in entityType.GetProperties(PublicInstance))
{
IndexAttribute[] indexAttributes = (IndexAttribute[])property.GetCustomAttributes(typeof(IndexAttribute), false);
NotMappedAttribute[] notMappedAttributes = (NotMappedAttribute[])property.GetCustomAttributes(typeof(NotMappedAttribute), false);
if (indexAttributes.Length > 0 && notMappedAttributes.Length == 0)
{
ColumnAttribute[] columnAttributes = (ColumnAttribute[])property.GetCustomAttributes(typeof(ColumnAttribute), false);
foreach (IndexAttribute indexAttribute in indexAttributes)
{
if (!indexes.ContainsKey(indexAttribute))
{
indexes.Add(indexAttribute, new List<string>());
}
if (property.PropertyType.IsValueType || property.PropertyType == typeof(string))
{
string columnName = columnAttributes.Length != 0 ? columnAttributes[0].Name : property.Name;
indexes[indexAttribute].Add(columnName);
}
else
{
indexes[indexAttribute].Add(property.PropertyType.Name + "_" + GetKeyName(property.PropertyType));
}
}
}
}
foreach (IndexAttribute indexAttribute in indexes.Keys)
{
query += CreateIndexQueryTemplate.Replace("{indexName}", indexAttribute.Name)
.Replace("{tableName}", tableName)
.Replace("{columnName}", string.Join(", ", indexes[indexAttribute].ToArray()))
.Replace("{unique}", indexAttribute.IsUnique ? "UNIQUE" : string.Empty);
}
}
if (context.Database.CreateIfNotExists())
{
context.Database.ExecuteSqlCommand(query);
}
}
private string GetKeyName(Type type)
{
PropertyInfo[] propertyInfos = type.GetProperties(BindingFlags.FlattenHierarchy | BindingFlags.Instance | BindingFlags.Public);
foreach (PropertyInfo propertyInfo in propertyInfos)
{
if (propertyInfo.GetCustomAttribute(typeof(KeyAttribute), true) != null)
return propertyInfo.Name;
}
throw new Exception("No property was found with the attribute Key");
}
}
然后在您的 dbcontext 中重载 OnModelCreating
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
Database.SetInitializer(new IndexInitializer<MyContext>());
base.OnModelCreating(modelBuilder);
}
将索引属性应用于您的实体类型,使用此解决方案,您可以在同一索引中拥有多个字段,只需使用相同的名称和唯一的即可。
在佩托伊扩张
我将 CreateIndexQueryTemplate 修改为
private const string CreateIndexQueryTemplate = "IF NOT EXISTS (SELECT name FROM sysindexes WHERE name = '{indexName}') CREATE {unique} INDEX {indexName} ON {tableName} ({columnName});";
并从 OnModelCreating 中删除了以下内容
Database.SetInitializer(new IndexInitializer<MyContext>());
并将以下内容添加到配置种子方法中
new IndexInitializer<MyContext>().InitializeDatabase(context);
这样,每次执行更新数据库时都会运行索引属性。
如果您希望将此功能添加到 EF,那么您可以在这里为它投票http://entityframework.codeplex.com/workitem/57
jwsadler 的数据注释扩展非常适合我们。 我们使用 Annotations 来影响类或属性的处理,并使用 Fluent API 来进行全局更改。
我们的注释涵盖索引(唯一的和非唯一的)以及 getdate() 和 (1) 的默认值。 代码示例展示了我们如何将其应用于我们的情况。 我们所有的类都继承自一个基类。 这个实现做了很多假设,因为我们有一个非常简单的模型。 我们使用的是实体框架 6.0.1。 许多评论已被包括在内。
using System;
using System.Linq;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
namespace YourNameSpace
{
public enum SqlOption
{
Active = 1,
GetDate = 2,
Index = 3,
Unique = 4,
}
[AttributeUsage(AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
public class SqlAttribute : Attribute
{
public SqlAttribute(SqlOption selectedOption = SqlOption.Index)
{
this.Option = selectedOption;
}
public SqlOption Option {get; set;}
}
// See enum above, usage examples: [Sql(SqlOption.Unique)] [Sql(SqlOption.Index)] [Sql(SqlOption.GetDate)]
public class SqlInitializer<T> : IDatabaseInitializer<T> where T : DbContext
{
// Create templates for the DDL we want generate
const string INDEX_TEMPLATE = "CREATE NONCLUSTERED INDEX IX_{columnName} ON [dbo].[{tableName}] ([{columnName}]);";
const string UNIQUE_TEMPLATE = "CREATE UNIQUE NONCLUSTERED INDEX UQ_{columnName} ON [dbo].[{tableName}] ([{columnName}]);";
const string GETDATE_TEMPLATE = "ALTER TABLE [dbo].[{tableName}] ADD DEFAULT (getdate()) FOR [{columnName}];";
const string ACTIVE_TEMPLATE = "ALTER TABLE [dbo].[{tableName}] ADD DEFAULT (1) FOR [{columnName}];";
// Called by Database.SetInitializer(new IndexInitializer< MyDBContext>()); in MyDBContext.cs
public void InitializeDatabase(T context)
{
// To be used for the SQL DDL that I generate
string sql = string.Empty;
// All of my classes are derived from my base class, Entity
var baseClass = typeof(Entity);
// Get a list of classes in my model derived from my base class
var modelClasses = AppDomain.CurrentDomain.GetAssemblies().ToList().
SelectMany(s => s.GetTypes()).Where(baseClass.IsAssignableFrom);
// For debugging only - examine the SQL DDL that Entity Framework is generating
// Manipulating this is discouraged.
var generatedDDSQL = ((IObjectContextAdapter)context).ObjectContext.CreateDatabaseScript();
// Define which Annotation Attribute we care about (this class!)
var annotationAttribute = typeof(SqlAttribute);
// Generate a list of concrete classes in my model derived from
// Entity class since we follow Table Per Concrete Class (TPC).
var concreteClasses = from modelClass in modelClasses
where !modelClass.IsAbstract
select modelClass;
// Iterate through my model's concrete classes (will be mapped to tables)
foreach (var concreteClass in concreteClasses)
{
// Calculate the table name - could get the table name from list of DbContext's properties
// to be more correct (but this is sufficient in my case)
var tableName = concreteClass.Name + "s";
// Get concrete class's properties that have this annotation
var propertiesWithAnnotations = concreteClass.GetProperties().Where(prop => Attribute.IsDefined(prop, annotationAttribute));
foreach (var annotatedProperty in propertiesWithAnnotations)
{
var columnName = annotatedProperty.Name;
var annotationProperties = annotatedProperty.GetCustomAttributes(annotationAttribute, true).ToList();
foreach (SqlAttribute annotationProperty in annotationProperties)
{
// Generate the appropriate SQL DLL based on the attribute selected
switch (annotationProperty.Option)
{
case SqlOption.Active: // Default value of true plus an index (for my case)
sql += ACTIVE_TEMPLATE.Replace("{tableName}", tableName).Replace("{columnName}", columnName);
sql += INDEX_TEMPLATE.Replace("{tableName}", tableName).Replace("{columnName}", columnName);
break;
case SqlOption.GetDate: // GetDate plus an index (for my case)
sql += GETDATE_TEMPLATE.Replace("{tableName}", tableName).Replace("{columnName}", columnName);
sql += INDEX_TEMPLATE.Replace("{tableName}", tableName).Replace("{columnName}", columnName);
break;
case SqlOption.Index: // Default for empty annotations for example [Sql()]
sql += INDEX_TEMPLATE.Replace("{tableName}", tableName).Replace("{columnName}", columnName);
break;
case SqlOption.Unique:
sql += UNIQUE_TEMPLATE.Replace("{tableName}", tableName).Replace("{columnName}", columnName);
break;
} // switch
} // foreach annotationProperty
} // foreach annotatedProperty
} // foreach concreteClass
// Would have been better not to go through all the work of generating the SQL
// if we weren't going to use it, but putting it here makes it easier to follow.
if (context.Database.CreateIfNotExists())
context.Database.ExecuteSqlCommand(sql);
} // InitializeDatabase
} // SqlInitializer
} // Namespace
这是我们的上下文:
using System;
using System.Data.Entity;
using System.Data.Entity.ModelConfiguration.Conventions;
namespace YourNameSpace
{
public class MyDBContext : DbContext
{
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
// Only including my concrete classes here as we're following Table Per Concrete Class (TPC)
public virtual DbSet<Attendance> Attendances { get; set; }
public virtual DbSet<Course> Courses { get; set; }
public virtual DbSet<Location> Locations { get; set; }
public virtual DbSet<PaymentMethod> PaymentMethods { get; set; }
public virtual DbSet<Purchase> Purchases { get; set; }
public virtual DbSet<Student> Students { get; set; }
public virtual DbSet<Teacher> Teachers { get; set; }
// Process the SQL Annotations
Database.SetInitializer(new SqlInitializer<MyDBContext>());
base.OnModelCreating(modelBuilder);
// Change all datetime columns to datetime2
modelBuilder.Properties<DateTime>().Configure(c => c.HasColumnType("datetime2"));
// Turn off cascading deletes
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
}
}
}
扩展上面 Tsuushin 的答案以支持多列和唯一约束:
private void CreateIndex(RBPContext context, string field, string table, bool unique = false)
{
context.Database.ExecuteSqlCommand(String.Format("CREATE {0}NONCLUSTERED INDEX IX_{1}_{2} ON {1} ({3})",
unique ? "UNIQUE " : "",
table,
field.Replace(",","_"),
field));
}
为了进一步构建所有这些出色的响应,我们添加了以下代码以允许从关联的元数据类型中提取 Index 属性。 有关完整的详细信息,请参阅我的博客文章,但总而言之,这里是详细信息。
元数据类型的使用方式如下:
[MetadataType(typeof(UserAccountAnnotations))]
public partial class UserAccount : IDomainEntity
{
[Key]
public int Id { get; set; } // Unique ID
sealed class UserAccountAnnotations
{
[Index("IX_UserName", unique: true)]
public string UserName { get; set; }
}
}
在这个例子中,元数据类型是一个嵌套类,但它不一定是,它可以是任何类型。 属性匹配仅通过名称完成,因此元数据类型只需具有相同名称的属性,然后应用到该属性的任何数据注释都应应用到关联的实体类。 这在原始解决方案中不起作用,因为它不检查关联的元数据类型。 我们研究了以下辅助方法:
/// <summary>
/// Gets the index attributes on the specified property and the same property on any associated metadata type.
/// </summary>
/// <param name="property">The property.</param>
/// <returns>IEnumerable{IndexAttribute}.</returns>
IEnumerable<IndexAttribute> GetIndexAttributes(PropertyInfo property)
{
Type entityType = property.DeclaringType;
var indexAttributes = (IndexAttribute[])property.GetCustomAttributes(typeof(IndexAttribute), false);
var metadataAttribute =
entityType.GetCustomAttribute(typeof(MetadataTypeAttribute)) as MetadataTypeAttribute;
if (metadataAttribute == null)
return indexAttributes; // No metadata type
Type associatedMetadataType = metadataAttribute.MetadataClassType;
PropertyInfo associatedProperty = associatedMetadataType.GetProperty(property.Name);
if (associatedProperty == null)
return indexAttributes; // No metadata on the property
var associatedIndexAttributes =
(IndexAttribute[])associatedProperty.GetCustomAttributes(typeof(IndexAttribute), false);
return indexAttributes.Union(associatedIndexAttributes);
}
我发现@highace 给出的答案存在问题 - 向下迁移对 DropIndex 使用了错误的覆盖。 这是我所做的:
这是包含每种方法的两种覆盖示例的代码:
public partial class AddUniqueIndexes : DbMigration
{
public override void Up()
{
//Sql Server limits indexes to 900 bytes,
//so we need to ensure cumulative field sizes do not exceed this
//otherwise inserts and updates could be prevented
//http://www.sqlteam.com/article/included-columns-sql-server-2005
AlterColumn("dbo.Answers",
"Text",
c => c.String(nullable: false, maxLength: 400));
AlterColumn("dbo.ConstructionTypes",
"Name",
c => c.String(nullable: false, maxLength: 300));
//[IX_Text] is the name that Entity Framework would use by default
// even if it wasn't specified here
CreateIndex("dbo.Answers",
"Text",
unique: true,
name: "IX_Text");
//Default name is [IX_Name_OrganisationID]
CreateIndex("dbo.ConstructionTypes",
new string[] { "Name", "OrganisationID" },
unique: true);
}
public override void Down()
{
//Drop Indexes before altering fields
//(otherwise it will fail because of dependencies)
//Example of dropping an index based on its name
DropIndex("dbo.Answers", "IX_Text");
//Example of dropping an index based on the columns it targets
DropIndex("dbo.ConstructionTypes",
new string[] { "Name", "OrganisationID" });
AlterColumn("dbo.ConstructionTypes",
"Name",
c => c.String(nullable: false));
AlterColumn("dbo.Answers",
"Text",
c => c.String(nullable: false, maxLength: 500));
}
您可以在 ModelBuilder 中指定索引
modelBuilder
.Entity<UserSalary>(builder =>
{
builder.HasNoKey();
builder.HasIndex("UserId").IsUnique(false);
builder.ToTable("UserSalary");
});
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