Alter a table (Java)

Alters a table by doing one of the following:

Adding one or more columns to a table
Dropping one or more columns from a table

You cannot change a column’s type. Instead, you must drop the column and add a new column.

Similarly, you cannot rename a table. Instead, you must drop and re-create the table.

After you add a column, you should index the column if you want to filter or sort on the column. For more information, see Create an index (Java) and Create a vector index (Java).

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

Adds or drops columns.

Returns a Table<T> instance that represents the table after the schema change.

Although the Table instance that you used to perform the alteration will still work, it will not reflect the updated typing if you added or dropped columns. To reflect the new typing, use the rowClass parameter.

Parameters

Use the alter method, which belongs to the com.datastax.astra.client.tables.Table class.

Method signature

Table<T> alter(AlterTableOperation operation)

Table<T> alter(
  AlterTableOperation operation,
  AlterTableOptions options
)

<R> Table<R> alter(
  AlterTableOperation operation,
  AlterTableOptions options,
  Class<R> clazz
)

Name Type Summary

Name	Type	Summary
`operation`	`AlterTableOperation`	The alter operation to perform. Can be one of the following: An `AlterTableAddColumns` object that specifies the columns to add. Column are defined in the same way as when you create a table. For examples, see Add columns to a table and Add vector columns to a table. An `AlterTableDropColumns` object that specifies the names of the columns to remove. For an example, see Drop columns from a table.
`options`	`AlterTableOptions`	Optional. The options for this operation, including the timeout.
`rowClass`	`Class<?>`	Optional. A specification of the class of the table’s row object. Default: `Row`, which is close to a `Map` object

operation

AlterTableOperation

The alter operation to perform.

Can be one of the following:

An AlterTableAddColumns object that specifies the columns to add. Column are defined in the same way as when you create a table.

For examples, see Add columns to a table and Add vector columns to a table.
An AlterTableDropColumns object that specifies the names of the columns to remove.

For an example, see Drop columns from a table.

options

AlterTableOptions

Optional. The options for this operation, including the timeout.

rowClass

Class<?>

Optional. A specification of the class of the table’s row object.

Default: Row, which is close to a Map object

Examples

The following examples demonstrate how to alter a table.

Add columns to a table

When you add columns, the columns are defined in the same way as they are when you create a table.

After you add a column, you should index the column if you want to filter or sort on the column. For more information, see Create an index (Java) and Create a vector index (Java).

import com.datastax.astra.client.DataAPIClients;
import com.datastax.astra.client.tables.Table;
import com.datastax.astra.client.tables.commands.AlterTableAddColumns;
import com.datastax.astra.client.tables.definition.rows.Row;

public class Example {

  public static void main(String[] args) {
    // Get an existing table
    Table<Row> table =
        DataAPIClients.clientHCD("USERNAME", "PASSWORD")
            .getDatabase("API_ENDPOINT", "KEYSPACE_NAME")
            .getTable("TABLE_NAME");

    // Add columns
    AlterTableAddColumns alterOperation =
        new AlterTableAddColumns()
            .addColumnBoolean("is_summer_reading")
            .addColumnText("library_branch");
    table.alter(alterOperation);
  }
}

Add vector columns to a table

After you add a vector column, you should index the column if you want run vector searches on the column. For more information, Create a vector index (Java).

import com.datastax.astra.client.DataAPIClients;
import com.datastax.astra.client.tables.Table;
import com.datastax.astra.client.tables.commands.AlterTableAddColumns;
import com.datastax.astra.client.tables.definition.columns.TableColumnDefinitionVector;
import com.datastax.astra.client.tables.definition.rows.Row;

public class Example {

  public static void main(String[] args) {
    // Get an existing table
    Table<Row> table =
        DataAPIClients.clientHCD("USERNAME", "PASSWORD")
            .getDatabase("API_ENDPOINT", "KEYSPACE_NAME")
            .getTable("TABLE_NAME");

    // Add a vector column
    AlterTableAddColumns alterOperation =
        new AlterTableAddColumns()
            .addColumnVector("example_vector", new TableColumnDefinitionVector().dimension(1024));
    table.alter(alterOperation);
  }
}

Drop columns from a table

Dropping columns produces tombstones. Excessive tombstones can impact query performance.

import com.datastax.astra.client.DataAPIClients;
import com.datastax.astra.client.tables.Table;
import com.datastax.astra.client.tables.commands.AlterTableDropColumns;
import com.datastax.astra.client.tables.definition.rows.Row;

public class Example {

  public static void main(String[] args) {
    // Get an existing table
    Table<Row> table =
        DataAPIClients.clientHCD("USERNAME", "PASSWORD")
            .getDatabase("API_ENDPOINT", "KEYSPACE_NAME")
            .getTable("TABLE_NAME");

    // Drop columns
    AlterTableDropColumns alterOperation =
        new AlterTableDropColumns("is_summer_reading", "library_branch");
    table.alter(alterOperation);
  }
}

Client reference

For more information, see the client reference.

Alter a table (Java)

Result

Parameters

Examples

Add columns to a table

Add vector columns to a table

Drop columns from a table

Client reference

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