Index support for complex type properties in EF Core migrations — the missing piece for value object-driven architectures.

EF Core 8.0 introduced complex properties, but migration tooling doesn't automatically generate indexes for these nested value objects. This NuGet package bridges that gap with a clean, fluent API for defining single-column, composite, unique, and filtered indexes directly on complex type properties — and, on PostgreSQL, expression (functional) indexes.

Why it matters:

• Value Object Indexing: Seamlessly add database indexes to properties buried inside complex types (e.g., Person.EmailAddress.Value)
• DDD-Friendly: Supports the Domain-Driven Design pattern of encapsulating logic in value objects without sacrificing database performance
• Migration-Aware: Automatically generates proper CREATE INDEX and DROP INDEX operations during EF Core migrations
• Flexible Filtering: Supports SQL WHERE clauses for filtered indexes (e.g., soft deletes)
• Composite Indexes: Define multi-column indexes spanning both scalar and nested properties with a single, intuitive expression — with per-column ASC/DESC ordering via DbOrder.Asc/DbOrder.Desc
• Expression Indexes (PostgreSQL): Index arbitrary SQL expressions such as lower(email) or to_tsvector('english', body) — including on plain, non-complex entities

Package	NuGet	Description
EFCore.ComplexIndexes		Core library — single-column, composite, unique, and filtered indexes on complex type properties. Works with any EF Core relational provider.
EFCore.ComplexIndexes.PostgreSQL		PostgreSQL extensions via Npgsql — adds GIN, GiST, BRIN, SP-GiST, and Hash index methods, operator classes, covering indexes (INCLUDE), concurrent creation, nulls-distinct control, and expression (functional) indexes.

Which package do I need? Install only the core package if you use SQL Server, SQLite, or any provider where the default B-tree index type is sufficient. Add the PostgreSQL package when you need PostgreSQL-specific index types or expression indexes — it includes the core automatically.

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Getting started

Complex-property indexes (core)

The complex-property, composite, and provider-method index features are wired up automatically through EF Core's design-time tooling. Just install the package, configure your indexes in OnModelCreating, and run dotnet ef migrations add — zero additional ceremony.

Expression indexes (PostgreSQL) — one-time setup

Expression indexes are the one exception: rendering CREATE INDEX … ((expr)) requires a custom migrations SQL generator that runs when migrations are applied. EF Core does not auto-wire runtime services, so you must opt in once when configuring your DbContext:

services.AddDbContext<AppDbContext>(options =>
    options
        .UseNpgsql(connectionString)
        .UseNpgsqlComplexIndexes());   // ← required for HasExpressionIndex(...)

⚠️ UseNpgsqlComplexIndexes() is a prerequisite for HasExpressionIndex. Without it, applying a migration that contains an expression index will fail (the stock generator can't render the expression). All other features — complex-property indexes, composite indexes, and the GIN/GiST/etc. methods — do not require this call; they flow through Npgsql's own SQL generator.

Using a custom Internal Service Provider? If your application builds its own IServiceProvider and passes it to .UseInternalServiceProvider(...), EF Core prevents .UseNpgsqlComplexIndexes() from modifying services. Instead, register the generator directly on your IServiceCollection:

var provider = new ServiceCollection()
.AddEntityFrameworkNpgsql()
.AddNpgsqlComplexIndexes() // ← Add this for expression indexes
.BuildServiceProvider();

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Usage

Single-column index on a complex property

builder.ComplexProperty(x => x.EmailAddress, c =>
    c.Property(x => x.Value)
     .HasComplexIndex(isUnique: true, filter: "deleted_at IS NULL")
);

Composite index across scalar and nested properties

builder.HasComplexCompositeIndex(
    x => new { x.Name, x.EmailAddress.Value },
    isUnique: true);

Per-column sort direction

Wrap any member in DbOrder.Desc(...) (or DbOrder.Asc(...), the default) to control its sort order. Because a wrapped member is a method call, C# requires you to name it in the anonymous type:

builder.HasComplexCompositeIndex(
    c => new { c.HybridDateTime.DateTime, Counter = DbOrder.Desc(c.HybridDateTime.Counter), c.Id },
    indexName: "IX_Commits_DateTime_Counter_Id");
// CREATE INDEX "IX_Commits_DateTime_Counter_Id" ON ... ("DateTime", "Counter" DESC, "Id");

Direction maps to EF Core's native CreateIndexOperation.IsDescending, so it is rendered by every relational provider (SQL Server, SQLite, PostgreSQL) — no extra wiring required. Re-declaring an index over the same columns updates its direction.

PostgreSQL index methods on a complex property

Use the builder-callback overload to reach the PostgreSQL-specific options (GIN, GiST, BRIN, SP-GiST, Hash, operator classes, INCLUDE, concurrent creation, nulls-distinct):

builder.ComplexProperty(x => x.Payload, c =>
    c.Property(x => x.Json)
     .HasComplexIndex(idx => idx
         .UseGin()
         .HasOperators("jsonb_path_ops"))
);

Expression (functional) indexes — PostgreSQL

Requires UseNpgsqlComplexIndexes() (see Getting started). Available as an extension on EntityTypeBuilder<TEntity>, so it works on any entity — complex or not.

Each string is emitted verbatim — there is no property-to-column resolution and no automatic quoting. Write the final SQL exactly as it should appear inside the index, referencing real column names.

Single expression:

// CREATE INDEX "IX_person_lowerlastname" ON person ((lower(last_name)));
builder.HasExpressionIndex("lower(last_name)");

With unique / filter / explicit name:

builder.HasExpressionIndex(
    "lower(email)",
    isUnique:  true,
    filter:    "deleted_at IS NULL",
    indexName: "ix_person_email_ci");

Multiple ordered parts + provider options (builder callback):

builder.HasExpressionIndex(idx => idx
    .Expression("country")            // a plain column, written as raw SQL
    .Expression("lower(email)")       // a SQL expression
    .IsUnique()
    .HasFilter("deleted_at IS NULL")
    .HasName("ix_person_country_email_ci"));
// CREATE UNIQUE INDEX "ix_person_country_email_ci"
//   ON person ((country), (lower(email)))
//   WHERE deleted_at IS NULL;

Full-text / JSONB with a GIN index:

builder.HasExpressionIndex(idx => idx
    .Expression("to_tsvector('english', body)")
    .UseGin());
// CREATE INDEX ... ON articles USING gin ((to_tsvector('english', body)));

Covering expression index (INCLUDE):

builder.HasExpressionIndex(idx => idx
    .Expression("lower(email)")
    .IsUnique()
    .IncludeProperties("display_name"));

Quoting tip

Strings are passed through untouched, so identifiers that need PostgreSQL quoting (e.g. PascalCase columns) must include the quotes yourself. C# raw string literals keep this readable:

// CREATE INDEX ... ON "People" ((lower("Email")));
builder.HasExpressionIndex(""" lower("Email") """.Trim());

Roadmap: the expression API is built on an IIndexExpression seam. A future LINQ add-on will let you write HasExpressionIndex(x => x.Email.ToLower()) and have it translated to SQL — flowing through the exact same pipeline.

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The package integrates seamlessly with EF Core's design-time tooling. Apart from the one-time UseNpgsqlComplexIndexes() call for expression indexes, there is no additional ceremony — just configure and migrate.