c# - 防止在多对多表上按约定创建索引

Question

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按约定创建的索引。

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

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。

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; }
}

Answer 1

事实证明，这是 not officially supported yet .

但是，解决方法是使用内部 EF API。它的使用需要注意，它可能会更改，恕不另行通知，因为它不适合外部使用。

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);
}

via Arthur Vickers

因为我的所有多对多实体都在同一个 Junctions 命名空间中，所以目前适用于我的实现是:

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);
}