dotnet/efcore · error · InvalidOperationException

A full-text index on '{entityType}' is defined over multiple

Error message

A full-text index on '{entityType}' is defined over multiple properties (`{properties}`). A full-text index can only target a single property.

What it means

Azure Cosmos DB full-text indexes can only target a single property path. During container creation (CosmosClientWrapper.cs:198-204), EF Core rejects any index where IsFullTextIndex() is true and Properties.Count exceeds 1. A composite full-text index is not supported by the Cosmos full-text policy schema.

Source

Thrown at src/EFCore.Cosmos/Storage/Internal/CosmosClientWrapper.cs:200

            {
                if (index.Properties.Count > 1)
                {
                    throw new InvalidOperationException(
                        CosmosStrings.CompositeVectorIndex(
                            index.DeclaringEntityType.DisplayName(),
                            string.Join(",", index.Properties.Select(e => e.Name))));
                }

                vectorIndexes.Add(
                    new VectorIndexPath { Path = GetJsonPropertyPathFromRoot(index.Properties[0]), Type = vectorIndexType.Value });
                continue;
            }

            if (index.IsFullTextIndex() == true)
            {
                if (index.Properties.Count > 1)
                {
                    throw new InvalidOperationException(
                        CosmosStrings.CompositeFullTextIndex(
                            index.DeclaringEntityType.DisplayName(),
                            string.Join(",", index.Properties.Select(e => e.Name))));
                }

                fullTextIndexPaths.Add(
                    new FullTextIndexPath { Path = GetJsonPropertyPathFromRoot(index.Properties[0]) });
                continue;
            }

            var isConvention = index is IConventionIndex convIndex
                && convIndex.GetConfigurationSource() == ConfigurationSource.Convention;

            if (index.Properties.Count == 1)
            {
                var path = GetJsonPropertyPathFromRoot(index.Properties[0]) + "/?";
                if (seenIncludedPaths.Add(path))
                {

View on GitHub (pinned to dbf9771522)

Solutions

1. Create a separate single-property full-text index for each property you want searchable: modelBuilder.Entity<T>().HasIndex(x => x.Title).ForCosmos().IsFullTextIndex(); and modelBuilder.Entity<T>().HasIndex(x => x.Body).ForCosmos().IsFullTextIndex().
2. Ensure each full-text index targets exactly one property.
3. Recreate the container after fixing the model.

Example fix

// before
modelBuilder.Entity<Article>()
    .HasIndex(a => new { a.Title, a.Body })
    .ForCosmos()
    .IsFullTextIndex();

// after
modelBuilder.Entity<Article>().HasIndex(a => a.Title).ForCosmos().IsFullTextIndex();
modelBuilder.Entity<Article>().HasIndex(a => a.Body).ForCosmos().IsFullTextIndex();

// Validate that no full-text index spans multiple properties.
foreach (var entityType in model.GetEntityTypes())
{
    foreach (var index in entityType.GetIndexes())
    {
        if (index.IsFullTextIndex() == true && index.Properties.Count > 1)
            throw new InvalidOperationException($"Full-text index on {entityType.DisplayName()} has multiple properties.");
    }
}

When it happens

Trigger: Configuring an index over multiple properties and enabling full-text search on it, e.g. modelBuilder.Entity<T>().HasIndex([x => x.Title, x => x.Body]).ForCosmos().IsFullTextIndex(). This fires at container-creation time.

Common situations: Wanting to full-text search across multiple text columns and assuming a composite index covers them. Copying a relational composite index and adding IsFullTextIndex(). Confusing full-text index (single property) with composite indexes (general purpose).

Related errors

• A vector index on '{entityType}' is defined over properties
• Creating a container with full-text search or vector propert
• Ordering based on scoring function is not supported inside '
• Only one ordering using scoring function is allowed. Use 'EF
• Ordering using a scoring function is mutually exclusive with

AI-assisted analysis of dotnet/efcore@dbf9771522 (2026-08-06). Data as JSON: /api/errors/cb9996b3cabaa7d7. Report an issue: GitHub.