Find a row (Java)

Finds a single row in a table using filter and sort clauses, including vector search.

For general information about working with tables and rows, see About tables with the Data API (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

Returns a row that matches the specified filter and sort clauses (Optional<R>), or returns Optional.empty() if no row was found.

If rowClass is not specified, then the type R is the same type as that of the rows in the table.

The columns included in the returned row depend on the subset of columns that were requested in the projection. If requested and applicable, the row will also include a $similarity key with a numeric similarity score that represents the closeness of the sort vector and the row’s vector.

Parameters

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

Method signature 
Optional<T> findOne(
  Filter filter
)
Optional<T> findOne(
  TableFindOneOptions options
)
Optional<T> findOne(
  Filter filter,
  TableFindOneOptions options
)
<R> Optional<R> findOne(
  Filter filter,
  Class<R> rowClass
)
<R> Optional<R> findOne(
  Filter filter,
  TableFindOneOptions options,
  Class<R> rowClass
)

For best performance, filter and sort on indexed columns, partition keys, and clustering keys.

Filtering on non-indexed columns is inefficient and resource-intensive, especially for large datasets. With the Data API clients, such operations can hit the client timeout limit before the underlying HTTP operation is complete. If you filter on non-indexed columns, the Data API will give a warning.

An empty filter or omitted filter may also result in an inefficient and long-running operation.

Additionally, the Data API can perform in-memory sorting, depending on the columns you sort on, the table’s partitioning structure, and whether the sorted columns are indexed. In-memory sorts can have performance implications.
Name Type Summary

filter

Filter

Optional. An object that defines filter criteria using the Data API filter syntax. The method only finds rows that match the filter criteria. Filters can improve performance by reducing the number of rows that the Data API processes.

For a list of available filter operators and more examples, see Filter operators for tables (Java).

To perform a vector search, use sort instead of filter.

To avoid fetching unnecessary rows, which can contain tombstones, DataStax recommends that you use a filter that limits the number of rows scanned. For example, filter on partition key columns or indexed columns.

Default: No filter

For an example, see Use filters to find a row.

rowClass

Class<?>

Optional. A specification of the class of the returned row object.

This parameter is useful if your code is strictly typed and you use a projection.

Default: The same class as the rows in the table. If you didn’t specify this when you instantiated the Table object, the row type defaulted to Row, which is close to a Map object.

options

TableFindOneOptions

Optional. The options for this operation. See Methods of the TableFindOneOptions class for more details.
Methods of the TableFindOneOptions class
Method Parameters Summary

sort()

Sort

Optional. Sorts rows by one or more columns, or performs a vector search.

For more information, see Sort clauses for tables (Java).

For examples, see Use sorting to find a row, Use vector search with a search vector to find a row, and Use vector search with a search string to find a row.

projection()

Projection

Optional. Controls which columns are included or excluded in the returned rows.

For more information, see Projections for tables (Java).

DataStax recommends a projection to avoid unnecessarily returning large columns, such as vector columns with highly dimensional embeddings.

Default: All columns

For examples, see Include only specific columns in the response and Exclude specific columns from the response.

includeSimilarity()

boolean

Optional. Whether to include a $similarity property in the response. The $similarity value represents the closeness of the sort vector and the row’s vector.

This parameter doesn’t work with vectorize; it only works if you provide the search vector for vector search directly.

Default: false

For an example, see Include the similarity score with the result.

timeout()

long | Duration

Optional. The timeout(s) to apply to HTTP request(s) originating from this method.

Default: The default value for the table. This default is 30 seconds unless you specified a different default when you initialized the Table or DataAPIClient object.

Examples

The following examples demonstrate how to find a row in a table.

Use filters to find a row

You can use a filter to find a row that matches specific criteria. For example, you can find a row with an is_checked_out value of false and a number_of_pages value less than 300.

For optimal performance, only filter on indexed columns. The Data API returns a warning if you filter on a non-indexed column.

For a list of available filter operators, see Filter operators for tables (Java).

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.core.query.Filter;
import com.datastax.astra.client.core.query.Filters;
import com.datastax.astra.client.tables.Table;
import com.datastax.astra.client.tables.definition.rows.Row;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing table
    Table<Row> table =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getTable("TABLE_NAME");

    // Find a row
    Filter filter =
        Filters.and(Filters.eq("is_checked_out", false), Filters.lt("number_of_pages", 300));

    Optional<Row> result = table.findOne(filter);

    System.out.println(result);
  }
}

Use vector search with a search vector to find a row

Perform a vector search by providing a search vector in the sort clause. This returns the row whose vector column value is most similar to the provided search vector.

The vector column must be indexed.

If your table has multiple vector columns, you can only sort on one vector column at a time.

You can use the DataAPIVector class to binary-encode your search vector. DataStax recommends that you always use a DataAPIVector object instead of a list of floats to improve performance.

When you read the value of a vector column, the client always returns a DataAPIVector object, unless you change the default serialization/deserialization behavior.

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.core.query.Sort;
import com.datastax.astra.client.core.vector.DataAPIVector;
import com.datastax.astra.client.tables.Table;
import com.datastax.astra.client.tables.commands.options.TableFindOneOptions;
import com.datastax.astra.client.tables.definition.rows.Row;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing table
    Table<Row> table =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getTable("TABLE_NAME");

    // Find a row
    TableFindOneOptions options =
        new TableFindOneOptions()
            .sort(
                Sort.vector(
                    "summary_genres_vector",
                    new DataAPIVector(new float[] {0.08f, -0.62f, 0.39f})));
    Optional<Row> result = table.findOne(options);
    System.out.println(result);
  }
}

Use vector search with a search string to find a row

Perform a vector search by providing a search string in the sort clause. The search string is converted to a search vector, and the row whose vector column value is most similar to the search vector is returned.

The vector column must have an embedding provider integration. You can configure embedding provider integrations when you create a table, add a vector column to an existing table, or alter an existing vector column. The vector column must be indexed.

If your table has multiple vector columns, you can only sort on one vector column at a time.

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.core.query.Sort;
import com.datastax.astra.client.tables.Table;
import com.datastax.astra.client.tables.commands.options.TableFindOneOptions;
import com.datastax.astra.client.tables.definition.rows.Row;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing table
    Table<Row> table =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getTable("TABLE_NAME");

    // Find a row
    TableFindOneOptions options =
        new TableFindOneOptions()
            .sort(Sort.vectorize("summary_genres_vector", "Text to vectorize"));

    Optional<Row> result = table.findOne(options);
    System.out.println(result);
  }
}

Use lexicographical matching to find a row

Lexicographical matching is currently in public preview. Development is ongoing, and the features and functionality are subject to change. Astra DB Serverless, and the use of such, is subject to the DataStax Preview Terms.

There are two ways to use lexicographical matching to find rows with the Data API:

  • Sort to find rows with a text or ascii column value that is most relevant to a given string of space-separated keywords or terms.

  • Filter with the $match operator to find rows with a text or ascii column value that is a lexicographical match to the specified string of space-separated keywords or terms

You can use these strategies together or separately.

Lexicographical matching is only available for text or ascii columns that have a text index, not a regular index. For more information, see Create a text index (Java) and Indexes in tables (Java).

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.core.query.Filter;
import com.datastax.astra.client.core.query.Filters;
import com.datastax.astra.client.core.query.Sort;
import com.datastax.astra.client.tables.Table;
import com.datastax.astra.client.tables.commands.options.TableFindOneOptions;
import com.datastax.astra.client.tables.definition.rows.Row;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing table
    Table<Row> table =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getTable("TABLE_NAME");

    // Find a row
    Filter filter = Filters.match("summary", "futuristic laboratory discovery");
    TableFindOneOptions options =
        new TableFindOneOptions().sort(Sort.lexical("summary", "futuristic laboratory"));

    Optional<Row> result = table.findOne(filter, options);
    System.out.println(result);
  }
}

Use sorting to find a row

You can use a sort clause to sort rows by one or more columns.

For best performance, only sort on columns that are indexed or that are part of the primary key.

For more information, see Sort clauses for tables (Java).

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.core.query.Filter;
import com.datastax.astra.client.core.query.Filters;
import com.datastax.astra.client.core.query.Sort;
import com.datastax.astra.client.tables.Table;
import com.datastax.astra.client.tables.commands.options.TableFindOneOptions;
import com.datastax.astra.client.tables.definition.rows.Row;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing table
    Table<Row> table =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getTable("TABLE_NAME");

    // Find a row
    Filter filter = Filters.eq("is_checked_out", false);
    TableFindOneOptions options =
        new TableFindOneOptions().sort(Sort.ascending("rating"), Sort.descending("title"));
    Optional<Row> result = table.findOne(filter, options);
    System.out.println(result);
  }
}

Include the similarity score with the result

If you use a vector search to find a row, you can also include a $similarity property in the result. The $similarity value represents the closeness of the sort vector and the value of the row’s vector column.

This parameter doesn’t work with vectorize; it only works if you provide the search vector for vector search directly.

The client always returns the similarity score as a DataAPIVector object, unless you change the default serialization/deserialization behavior.

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.core.query.Sort;
import com.datastax.astra.client.core.vector.DataAPIVector;
import com.datastax.astra.client.tables.Table;
import com.datastax.astra.client.tables.commands.options.TableFindOneOptions;
import com.datastax.astra.client.tables.definition.rows.Row;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing table
    Table<Row> table =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getTable("TABLE_NAME");

    // Find a row
    TableFindOneOptions options =
        new TableFindOneOptions()
            .sort(
                Sort.vector(
                    "summary_genres_vector", new DataAPIVector(new float[] {0.08f, -0.62f, 0.39f})))
            .includeSimilarity(true);

    Optional<Row> result = table.findOne(options);

    if (result.isPresent()) {
      Row row = result.get();

      Double similarity = row.getDouble("$similarity");

      System.out.println(similarity);
    }
  }
}

Include only specific columns in the response

To specify which columns to include or exclude in the returned row, use a projection.

The following example demonstrates an inclusive projection.

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.core.query.Filter;
import com.datastax.astra.client.core.query.Filters;
import com.datastax.astra.client.core.query.Projection;
import com.datastax.astra.client.tables.Table;
import com.datastax.astra.client.tables.commands.options.TableFindOneOptions;
import com.datastax.astra.client.tables.definition.rows.Row;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing table
    Table<Row> table =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getTable("TABLE_NAME");

    // Find a row
    Filter filter = Filters.lt("number_of_pages", 300);
    TableFindOneOptions options =
        new TableFindOneOptions().projection(Projection.include("is_checked_out", "title"));
    Optional<Row> result = table.findOne(filter, options);
    System.out.println(result);
  }
}

Exclude specific columns from the response

To specify which columns to include or exclude in the returned row, use a projection.

The following example demonstrates an exclusive projection.

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.core.query.Filter;
import com.datastax.astra.client.core.query.Filters;
import com.datastax.astra.client.core.query.Projection;
import com.datastax.astra.client.tables.Table;
import com.datastax.astra.client.tables.commands.options.TableFindOneOptions;
import com.datastax.astra.client.tables.definition.rows.Row;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing table
    Table<Row> table =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getTable("TABLE_NAME");

    // Find a row
    Filter filter = Filters.lt("number_of_pages", 300);
    TableFindOneOptions options =
        new TableFindOneOptions().projection(Projection.exclude("is_checked_out", "title"));
    Optional<Row> result = table.findOne(filter, options);
    System.out.println(result);
  }
}

Use filter, sort, and projection together

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.core.query.Filter;
import com.datastax.astra.client.core.query.Filters;
import com.datastax.astra.client.core.query.Projection;
import com.datastax.astra.client.core.query.Sort;
import com.datastax.astra.client.tables.Table;
import com.datastax.astra.client.tables.commands.options.TableFindOneOptions;
import com.datastax.astra.client.tables.definition.rows.Row;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing table
    Table<Row> table =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getTable("TABLE_NAME");

    // Find a row
    Filter filter =
        Filters.and(Filters.eq("is_checked_out", false), Filters.lt("number_of_pages", 300));
    TableFindOneOptions options =
        new TableFindOneOptions()
            .sort(Sort.ascending("rating"), Sort.descending("title"))
            .projection(Projection.include("is_checked_out", "title"));
    Optional<Row> result = table.findOne(filter, options);
    System.out.println(result);
  }
}

Client reference

For more information, see the client reference.

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