防止按约定在多对多表上创建索引 [英] Prevent index created by convention on many-to-many table

问题描述

在下面的配置中，EF 按照约定在 SyntaxId 上创建索引.由于我有一个复合主键(用作索引)并且没有标识列，因此我认为在多对多表中不需要在单个列上使用约定创建的索引.

In the configuration below, EF creates an index on SyntaxId by convention. Since I have a composite primary key (serves as index) and no identity column, I do not think this convention-created index on a single column is needed in a many-to-many table.

如何防止自动创建此约定索引 (b.HasIndex("SyntaxId");)?

How can I prevent this convention index (b.HasIndex("SyntaxId");) from being auto-created?

public class SoftwareSyntaxTypeConfiguration : BaseJunctionTypeConfiguration<SoftwareSyntax>
{
    public override void Configure(EntityTypeBuilder<SoftwareSyntax> entityTypeBuilder)
    {
        base.Configure(entityTypeBuilder);
        entityTypeBuilder.ToTable("software_syntaxes");
        entityTypeBuilder.HasKey(x => new {x.SoftwareId, x.SyntaxId});
        entityTypeBuilder.HasOne(x => x.Software)
                         .WithMany(x => x.SoftwareSyntaxes)
                         .HasForeignKey(x => x.SoftwareId);
        entityTypeBuilder.HasOne(x => x.Syntax)
                         .WithMany(x => x.SoftwareSyntaxes)
                         .HasForeignKey(x => x.SyntaxId);
    }
}

partial class FilterListsDbContextModelSnapshot : ModelSnapshot
{
    protected override void BuildModel(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity("FilterLists.Data.Entities.Junctions.SoftwareSyntax", b =>
            {
                b.Property<int>("SoftwareId");

                b.Property<int>("SyntaxId");

                b.HasKey("SoftwareId", "SyntaxId");

                b.HasIndex("SyntaxId"); //TODO: prevent this from being auto-created

                b.ToTable("software_syntaxes");
            });
    }
}

更新:添加实体类以进行说明.

Update: Adding entity classes for clarification.

public class Software
{
    public int Id { get; set; }
    public ICollection<SoftwareSyntax> SoftwareSyntaxes { get; set; }
    ...
}

public class Syntax
{
    public int Id { get; set; }
    public ICollection<SoftwareSyntax> SoftwareSyntaxes { get; set; }
    ...
}

public class SoftwareSyntax
{
    public int SoftwareId { get; set; }
    public Software Software { get; set; }

    public int SyntaxId { get; set; }
    public Syntax Syntax { get; set; }
}

推荐答案

事实证明，这是 尚未正式支持.

不过，一种解决方法是使用内部 EF API.它的使用需要注意的是，它可能会更改，恕不另行通知，因为它不适合外用.

A workaround, though, is to use an internal EF API. Its use carries the caveat that it could be changed without notice as it is not intended for external use.

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    ((Model)modelBuilder.Model).ConventionDispatcher.StartBatch();
    foreach (var entityType in modelBuilder.Model.GetEntityTypes())
    foreach (var index in entityType.GetIndexes().ToList())
        // if index is one you want to remove
            entityType.RemoveIndex(index.Properties);
}

通过亚瑟·维克斯

由于我的所有多对多实体都在同一个 Junctions 命名空间中，因此目前对我有用的实现是:

Since I have all of my many-to-many entities in the same Junctions namespace, the implementation that works for me currently is:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    ((Model)modelBuilder.Model).ConventionDispatcher.StartBatch();
    foreach (var entityType in modelBuilder.Model.GetEntityTypes())
    foreach (var index in entityType.GetIndexes().ToList())
        if (index.DeclaringEntityType.Name.Contains("Junctions"))
            entityType.RemoveIndex(index.Properties);
}

这篇关于防止按约定在多对多表上创建索引的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！