Create an index (C#)

Creates a new index for a column in a table in a database.

You should index any column that you want to sort or filter on that isn’t part of the primary key. Columns that are part of the primary key do not require a secondary index.

To create an index on a vector column, see Create a vector index (C#) instead.

To index a text column for lexicographical matching, see Create a text index (C#) instead.

To manage indexes, your application token must have the same level of permissions that you need to manage tables.

Ready to write code? See the examples for this method to get started. If you are new to the Data API, check out the quickstart.

Result

Creates an index for the specified column.

Does not return anything.

Parameters

Use the CreateIndexAsync method, which belongs to the Table class. You can also use CreateIndex, which is the synchronous version of the method.

Method signature

public Task CreateIndexAsync(
  string indexName, string columnName, CreateIndexOptions options = null
);

public Task CreateIndexAsync(
  string indexName,
  string columnName,
  TableIndexDefinition indexDefinition,
  CreateIndexOptions options = null
);

public Task CreateIndexAsync<TColumn>(
  string indexName,
  Expression<Func<T, TColumn>> column,
  CreateIndexOptions options = null
);

public Task CreateIndexAsync<TColumn>(
  string indexName,
  Expression<Func<T, TColumn>> column,
  TableIndexDefinition indexDefinition,
  CreateIndexOptions options = null
);

Name Type Summary

Name	Type	Summary
`indexName`	`string`	The name of the index. Index names for tables must follow these rules: Must be unique within the keyspace Can contain letters, numbers, and underscores Must have a length of 1 to 100 characters
`columnName`	`string`	The name of the table column on which to create the index. For `map` columns, you can index the entries, only the keys, or only the values. For an example, see Create an index for a map column. To create vector indexes based on `vector` columns, see Create a vector index (C#).
`column`	`Expression<Func<T, TColumn>>`	A lambda expression that indicates the table column on which to create the index. For `map` columns, you can index the entries, only the keys, or only the values. For an example, see Create an index for a map column. To create vector indexes based on `vector` columns, see Create a vector index (C#).
`indexDefinition`	`TableIndexDefinition`	Definition of the index to create. You can use `Builders.TableIndex.Index()` methods to create the `TableIndexDefinition` for non-map columns, and `Builders.TableIndex.Map()` for map columns. See Parameters of `Builders.TableIndex.Index()` for creating `TableIndexDefinition` and Parameters of `Builders.TableIndex.Map()` for creating `TableIndexDefinition` for more details.
`options`	`CreateIndexOptions`	Optional. Options for this operation. For more information and examples for general options such as timeout, see Customize API interaction. For options specific to this method, see Method-specific properties of the `CreateIndexOptions` class.

indexName

string

The name of the index.

Index names for tables must follow these rules:

Must be unique within the keyspace
Can contain letters, numbers, and underscores
Must have a length of 1 to 100 characters

columnName

string

The name of the table column on which to create the index.

For map columns, you can index the entries, only the keys, or only the values. For an example, see Create an index for a map column.

To create vector indexes based on vector columns, see Create a vector index (C#).

column

Expression<Func<T, TColumn>>

A lambda expression that indicates the table column on which to create the index.

For map columns, you can index the entries, only the keys, or only the values. For an example, see Create an index for a map column.

To create vector indexes based on vector columns, see Create a vector index (C#).

indexDefinition

TableIndexDefinition

Definition of the index to create.

You can use Builders.TableIndex.Index() methods to create the TableIndexDefinition for non-map columns, and Builders.TableIndex.Map() for map columns. See Parameters of Builders.TableIndex.Index() for creating TableIndexDefinition and Parameters of Builders.TableIndex.Map() for creating TableIndexDefinition for more details.

options

CreateIndexOptions

Optional. Options for this operation. For more information and examples for general options such as timeout, see Customize API interaction. For options specific to this method, see Method-specific properties of the CreateIndexOptions class.

Parameters of `Builders.TableIndex.Index()` for creating `TableIndexDefinition`
Name	Type	Summary
`options`	`TableIndexOptions`	Optional. Specifies index options for text and ASCII types. For examples, see Create an index and specify ASCII conversion before indexing, Create an index and specify Unicode normalization, and Create an index and specify case sensitivity.

Parameters of `Builders.TableIndex.Map()` for creating `TableIndexDefinition`
Name	Type	Summary
`mapIndexType`	`MapIndexType`	Whether to index the entries, only the keys, or only the values. For an example, see Create an index for a map column.
`options`	`TableIndexOptions`	Optional. Specifies index options for text and ASCII types. For examples, see Create an index and specify ASCII conversion before indexing, Create an index and specify Unicode normalization, and Create an index and specify case sensitivity.

Method-specific properties of the `CreateIndexOptions` class
Name	Type	Summary
`IfNotExists`	`bool`	Optional. Whether the command should silently succeed even if an index with the given name already exists in the keyspace and no new index was created. This option only checks index names. It does not check index definitions. For an example, see Create an index only if the index does not exist. Default: false

Examples

The following examples demonstrate how to create an index.

Create an index

using DataStax.AstraDB.DataApi;
using DataStax.AstraDB.DataApi.Tables;

namespace Examples;

public class Program
{
  static async Task Main()
  {
    // Get an existing table
    var client = new DataAPIClient();
    var database = client.GetDatabase(
      "API_ENDPOINT",
      "APPLICATION_TOKEN"
    );
    var table = database.GetTable("TABLE_NAME");

    // Index a column
    await table.CreateIndexAsync("INDEX_NAME", "COLUMN_NAME");
  }
}

Create an index and specify ASCII conversion before indexing

When you index a text or ASCII column, you can specify whether to convert non-ASCII characters to their US-ASCII equivalent before indexing.

Converting non-ASCII characters can improve search performance by limiting the range of allowed ASCII characters. This option is best for ASCII-only data or ASCII-only applications where you can safely ignore non-ASCII characters. It is not recommended for multilingual data or applications that must support non-ASCII characters.

For more information, see Index options for text and ASCII types.

using DataStax.AstraDB.DataApi;
using DataStax.AstraDB.DataApi.Core;
using DataStax.AstraDB.DataApi.Tables;

namespace Examples;

public class Program
{
  static async Task Main()
  {
    // Get an existing table
    var client = new DataAPIClient();
    var database = client.GetDatabase(
      "API_ENDPOINT",
      "APPLICATION_TOKEN"
    );
    var table = database.GetTable("TABLE_NAME");

    // Index a column
    await table.CreateIndexAsync(
      "INDEX_NAME",
      "COLUMN_NAME",
      Builders.TableIndex.Index(new TableIndexOptions() { Ascii = true })
    );
  }
}

Create an index and specify Unicode normalization

When you index a text or ASCII column, you can specify whether to normalize Unicode characters and diacritics before indexing.

Normalizing Unicode characters can improve search consistency and inclusivity. This option is best for datasets that can contain multiple Unicode versions of the same character, such as multilingual data or non-standardized user input.

For more information, see Index options for text and ASCII types.

using DataStax.AstraDB.DataApi;
using DataStax.AstraDB.DataApi.Core;
using DataStax.AstraDB.DataApi.Tables;

namespace Examples;

public class Program
{
  static async Task Main()
  {
    // Get an existing table
    var client = new DataAPIClient();
    var database = client.GetDatabase(
      "API_ENDPOINT",
      "APPLICATION_TOKEN"
    );
    var table = database.GetTable("TABLE_NAME");

    // Index a column
    await table.CreateIndexAsync(
      "INDEX_NAME",
      "COLUMN_NAME",
      Builders.TableIndex.Index(
        new TableIndexOptions() { Normalize = true }
      )
    );
  }
}

Create an index and specify case sensitivity

When you index a text or ASCII column, you can specify whether the index is case sensitive.

Enforcing case sensitivity is best for datasets where you want to enforce exact matches based on capitalization.

For more information, see Index options for text and ASCII types.

using DataStax.AstraDB.DataApi;
using DataStax.AstraDB.DataApi.Core;
using DataStax.AstraDB.DataApi.Tables;

namespace Examples;

public class Program
{
  static async Task Main()
  {
    // Get an existing table
    var client = new DataAPIClient();
    var database = client.GetDatabase(
      "API_ENDPOINT",
      "APPLICATION_TOKEN"
    );
    var table = database.GetTable("TABLE_NAME");

    // Index a column
    await table.CreateIndexAsync(
      "INDEX_NAME",
      "COLUMN_NAME",
      Builders.TableIndex.Index(
        new TableIndexOptions() { CaseSensitive = false }
      )
    );
  }
}

Create an index for a map column

For map columns, you can index the entries, only the keys, or only the values.

To index the entries, specify the column name as demonstrated in the "Create an index" example.

To index only the keys, specify the column name along with $keys:

using DataStax.AstraDB.DataApi;
using DataStax.AstraDB.DataApi.Core;
using DataStax.AstraDB.DataApi.Tables;

namespace Examples;

public class Program
{
  static async Task Main()
  {
    // Get an existing table
    var client = new DataAPIClient();
    var database = client.GetDatabase(
      "API_ENDPOINT",
      "APPLICATION_TOKEN"
    );
    var table = database.GetTable("TABLE_NAME");

    // Index a column
    await table.CreateIndexAsync(
      "INDEX_NAME",
      "MAP_COLUMN_NAME",
      Builders.TableIndex.Map(MapIndexType.Keys)
    );
  }
}

To index only the values, specify the column name along with $values:

using DataStax.AstraDB.DataApi;
using DataStax.AstraDB.DataApi.Core;
using DataStax.AstraDB.DataApi.Tables;

namespace Examples;

public class Program
{
  static async Task Main()
  {
    // Get an existing table
    var client = new DataAPIClient();
    var database = client.GetDatabase(
      "API_ENDPOINT",
      "APPLICATION_TOKEN"
    );
    var table = database.GetTable("TABLE_NAME");

    // Index a column
    await table.CreateIndexAsync(
      "INDEX_NAME",
      "MAP_COLUMN_NAME",
      Builders.TableIndex.Map(MapIndexType.Values)
    );
  }
}

Create an index only if the index does not exist

Use this option to silently do nothing if an index with the specified name already exists.

This option only checks index names. It doesn’t check the type or content of any existing indexes.

using DataStax.AstraDB.DataApi;
using DataStax.AstraDB.DataApi.Tables;

namespace Examples;

public class Program
{
  static async Task Main()
  {
    // Get an existing table
    var client = new DataAPIClient();
    var database = client.GetDatabase(
      "API_ENDPOINT",
      "APPLICATION_TOKEN"
    );
    var table = database.GetTable("TABLE_NAME");

    // Index a column
    await table.CreateIndexAsync(
      "INDEX_NAME",
      "COLUMN_NAME",
      new CreateIndexOptions() { IfNotExists = true }
    );
  }
}

Client reference

For more information, see the client reference.

Create an index (C#)

Result

Parameters

Examples

Create an index

Create an index and specify ASCII conversion before indexing

Create an index and specify Unicode normalization

Create an index and specify case sensitivity

Create an index for a map column

Create an index only if the index does not exist

Client reference

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