Find a document (Java)

Finds a single document in a collection using filter and sort clauses, including vector search.

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 document that matches the specified filter and sort clauses (Optional<T>), or returns Optional.empty() if no document was found.

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

Parameters

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

Method signature 
Optional<T> findOne(Filter filter)
Optional<T> findOne(
  Filter filter,
  CollectionFindOneOptions options
)
Optional<T> findOne(CollectionFindOneOptions options)
Name Type Summary

filter

Filter

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

You must use & to escape any . or & in field names in the filter clause. You cannot use & to escape any other characters. For more information, see Work with . and & in field names (Java).

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

Filters can use only indexed fields. If you apply selective indexing when you create a collection, you cannot reference non-indexed fields in a filter.

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

options

CollectionFindOneOptions

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

sort()

float[] | String | Sort | Map<String, Object>

Optional. Sorts documents by one or more fields, or performs a vector search.

You must use & to escape any . or & in field names in the sort clause. You cannot use & to escape any other characters. For more information, see Work with . and & in field names (Java).

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

Sort clauses can use only indexed fields. If you apply selective indexing when you create a collection, you cannot reference non-indexed fields in sort queries.

For vector searches, this parameter can use either $vector or $vectorize.

For examples, see Use sorting to find a document, Use vector search to find a document, and Use vector search and vectorize to find a document.

projection()

Projection

Optional. Controls which fields are included or excluded in the returned document.

You must use & to escape any . or & in field names in the projection clause. You cannot use & to escape any other characters. For more information, see Work with . and & in field names (Java).

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

Default: The default projection for the collection. All fields prefixed with $ are excluded by default and will only be returned if you include them in the projection. _id is included by default and will always be returned unless you exclude it from the projection.

For examples, see Include only specific fields in the response and Exclude specific fields 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 document’s vector.

This parameter only applies if you use a vector search.

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

Default: False

Examples

The following examples demonstrate how to find a document in a collection.

Use a document’s ID to find a document

All documents have a unique _id property. You can use a filter to find a document with a specific _id.

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.collections.Collection;
import com.datastax.astra.client.collections.definition.documents.Document;
import com.datastax.astra.client.core.query.Filter;
import com.datastax.astra.client.core.query.Filters;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing collection
    Collection<Document> collection =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getCollection("COLLECTION_NAME");

    // Find a document
    Filter filter = Filters.eq("_id", "101");
    Optional<Document> result = collection.findOne(filter);
    System.out.println(result);
  }
}

Use filters to find a document

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

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

Filters can use only indexed fields. If you apply selective indexing when you create a collection, you cannot reference non-indexed fields in a filter.

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.collections.Collection;
import com.datastax.astra.client.collections.definition.documents.Document;
import com.datastax.astra.client.core.query.Filter;
import com.datastax.astra.client.core.query.Filters;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing collection
    Collection<Document> collection =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getCollection("COLLECTION_NAME");

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

    Optional<Document> result = collection.findOne(filter);

    System.out.println(result);
  }
}

Use vector search to find a document

To find the document whose $vector value is most similar to a given vector, use a sort with the vector embeddings that you want to match. For more information, see Find data with vector search.

Vector search is only available for vector-enabled collections. For more information, see Create a collection that can store vector embeddings and $vector in collections (Java).

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.collections.Collection;
import com.datastax.astra.client.collections.commands.options.CollectionFindOneOptions;
import com.datastax.astra.client.collections.definition.documents.Document;
import com.datastax.astra.client.core.query.Sort;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing collection
    Collection<Document> collection =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getCollection("COLLECTION_NAME");

    // Find a document
    CollectionFindOneOptions options =
        new CollectionFindOneOptions().sort(Sort.vector(new float[] {0.08f, -0.62f, 0.39f}));
    Optional<Document> result = collection.findOne(options);
    System.out.println(result);
  }
}

Use vector search and vectorize to find a document

To find the document whose $vector value is most similar to the $vector value of a given search string, use a sort with the search string that you want to vectorize and match. For more information, see Find data with vector search.

Vector search with vectorize is only available for collections that have vectorize enabled. For more information, see Create a collection that can automatically generate vector embeddings and $vectorize in collections (Java).

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.collections.Collection;
import com.datastax.astra.client.collections.commands.options.CollectionFindOneOptions;
import com.datastax.astra.client.collections.definition.documents.Document;
import com.datastax.astra.client.core.query.Sort;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing collection
    Collection<Document> collection =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getCollection("COLLECTION_NAME");

    // Find a document
    CollectionFindOneOptions options =
        new CollectionFindOneOptions().sort(Sort.vectorize("Text to vectorize"));
    Optional<Document> result = collection.findOne(options);
    System.out.println(result);
  }
}

Use lexicographical matching to find a document

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 documents with the Data API:

You can use these strategies together or separately.

You can only use lexicographical matching on collections that have lexical enabled. For more information, see Create a collection that supports lexicographical matching.

Documents must have the $lexical field populated to be included in lexicographical matching. For examples, see Insert a document for retrieval with lexicographical matching and Insert documents for retrieval with lexicographical matching.

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.collections.Collection;
import com.datastax.astra.client.collections.commands.options.CollectionFindOneOptions;
import com.datastax.astra.client.collections.definition.documents.Document;
import com.datastax.astra.client.core.query.Filters;
import com.datastax.astra.client.core.query.Sort;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing collection
    Collection<Document> collection =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getCollection("COLLECTION_NAME");

    // Find a document
    CollectionFindOneOptions options =
        new CollectionFindOneOptions().sort(Sort.lexical("tree hill grassy"));
    Optional<Document> result = collection.findOne(Filters.match("tree hill"), options);
    System.out.println(result);
  }
}

Use sorting to find a document

You can use a sort clause to sort documents by one or more fields.

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

Sort clauses can use only indexed fields. If you apply selective indexing when you create a collection, you cannot reference non-indexed fields in sort queries.

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.collections.Collection;
import com.datastax.astra.client.collections.commands.options.CollectionFindOneOptions;
import com.datastax.astra.client.collections.definition.documents.Document;
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 java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing collection
    Collection<Document> collection =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getCollection("COLLECTION_NAME");

    // Find a document
    Filter filter = Filters.eq("metadata.language", "English");
    CollectionFindOneOptions options =
        new CollectionFindOneOptions().sort(Sort.ascending("rating"), Sort.descending("title"));
    Optional<Document> result = collection.findOne(filter, options);
    System.out.println(result);
  }
}

Include the similarity score with the result

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

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.collections.Collection;
import com.datastax.astra.client.collections.commands.options.CollectionFindOneOptions;
import com.datastax.astra.client.collections.definition.documents.Document;
import com.datastax.astra.client.core.query.Sort;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing collection
    Collection<Document> collection =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getCollection("COLLECTION_NAME");

    // Find a document
    CollectionFindOneOptions options =
        new CollectionFindOneOptions()
            .sort(Sort.vectorize("Text to vectorize"))
            .includeSimilarity(true);

    Optional<Document> result = collection.findOne(options);

    if (result.isPresent()) {
      Document document = result.get();

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

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

Include only specific fields in the response

To specify which fields to include or exclude in the returned document, use a projection.

All fields prefixed with $ are excluded by default and will only be returned if you include them in the projection. _id is included by default and will always be returned unless you exclude it from the projection.

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.collections.Collection;
import com.datastax.astra.client.collections.commands.options.CollectionFindOneOptions;
import com.datastax.astra.client.collections.definition.documents.Document;
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 java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing collection
    Collection<Document> collection =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getCollection("COLLECTION_NAME");

    // Find a document
    Filter filter = Filters.eq("metadata.language", "English");
    CollectionFindOneOptions options =
        new CollectionFindOneOptions().projection(Projection.include("is_checked_out", "title"));
    Optional<Document> result = collection.findOne(filter, options);
    System.out.println(result);
  }
}

Exclude specific fields from the response

To specify which fields to include or exclude in the returned document, use a projection.

All fields prefixed with $ are excluded by default and will only be returned if you include them in the projection. _id is included by default and will always be returned unless you exclude it from the projection.

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.collections.Collection;
import com.datastax.astra.client.collections.commands.options.CollectionFindOneOptions;
import com.datastax.astra.client.collections.definition.documents.Document;
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 java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing collection
    Collection<Document> collection =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getCollection("COLLECTION_NAME");

    // Find a document
    Filter filter = Filters.eq("metadata.language", "English");
    CollectionFindOneOptions options =
        new CollectionFindOneOptions().projection(Projection.exclude("is_checked_out", "title"));
    Optional<Document> result = collection.findOne(filter, options);
    System.out.println(result);
  }
}

Use filter, sort, and projection together

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.collections.Collection;
import com.datastax.astra.client.collections.commands.options.CollectionFindOneOptions;
import com.datastax.astra.client.collections.definition.documents.Document;
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 java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing collection
    Collection<Document> collection =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getCollection("COLLECTION_NAME");

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

Work with . and & in field names

You must use & to escape any . or & in field names when the field is used in a filter, sort, projection, update, or indexing clause. Dot notation, which is used to reference nested fields, should not be escaped. For more information, see Work with . and & in field names (Java).

For example, in the following document, you would use escaping like this: areas.r&&d, costs.price&.usd, and costs.price&.cad.

{
  "areas": {
    "r&d": true,
    "design": false
  },
  "costs": {
    "price.usd": 100,
    "price.cad": 90
  }
}
import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.collections.Collection;
import com.datastax.astra.client.collections.commands.options.CollectionFindOneOptions;
import com.datastax.astra.client.collections.definition.documents.Document;
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 java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing collection
    Collection<Document> collection =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getCollection("COLLECTION_NAME");

    // Find a document
    Filter filter =
        Filters.and(Filters.eq("areas.r&&d", false), Filters.lt("costs.price&.usd", 300));
    CollectionFindOneOptions options =
        new CollectionFindOneOptions()
            .sort(Sort.ascending("costs.price&.usd"))
            .projection(Projection.include("areas.r&&d", "costs.price&.cad"));
    Optional<Document> result = collection.findOne(filter, options);
    System.out.println(result);
  }
}

You can also use the escapeFieldNames function provided by the client:

import com.datastax.astra.client.DataAPIClient;
import com.datastax.astra.client.collections.Collection;
import com.datastax.astra.client.collections.commands.options.CollectionFindOneOptions;
import com.datastax.astra.client.collections.definition.documents.Document;
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.internal.utils.EscapeUtils;
import java.util.Optional;

public class Example {

  public static void main(String[] args) {
    // Get an existing collection
    Collection<Document> collection =
        new DataAPIClient("APPLICATION_TOKEN")
            .getDatabase("API_ENDPOINT")
            .getCollection("COLLECTION_NAME");

    // Find a document
    Filter filter =
        Filters.and(
            Filters.eq(EscapeUtils.escapeFieldNames("areas", "r&d"), false),
            Filters.lt(EscapeUtils.escapeFieldNames("costs", "price.usd"), 300));
    CollectionFindOneOptions options =
        new CollectionFindOneOptions()
            .sort(Sort.ascending(EscapeUtils.escapeFieldNames("costs", "price.usd")))
            .projection(
                Projection.include(
                    EscapeUtils.escapeFieldNames("areas", "r&d"),
                    EscapeUtils.escapeFieldNames("costs", "price.cad")));
    Optional<Document> result = collection.findOne(filter, options);
    System.out.println(result);
  }
}

Client reference

For more information, see the client reference.

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