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Document API
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This is an introduction to how to build and compile Vespa clients using the Document API. It can be used for feeding, updating and retrieving documents, or removing documents from the repository. See also the Java reference.

Documents

All data fed, indexed and searched in Vespa are instances of the Document class. A document is a composite object that consists of:

  • A DocumentType that defines the set of fields that can exist in a document. A document can only have a single document type, but document types can inherit the content of another. All fields of an inherited type is available in all its descendants. The document type definition is derived from the search definition, which is converted into a configuration file to be read by the DocumentManager.

    All registered document types are instantiated and stored within the document manager. A reference to these objects can be retrieved using the getDocumentType() method by supplying the name and the version of the wanted document type.

    DocumentManager initialization is done automatically by the Document API by subscribing to the appropriate configuration.

  • A DocumentId which is a unique document identifier. The document distribution uses the document identifier, see the reference for details.

  • A set of (Field, FieldValue) pairs, or "fields" for short. The Field class has methods for getting its name, data type and internal identifier. The field object for a given field name can be retrieved using the getField(<fieldname>) method in the DocumentType.

Use DocumentAccess javadoc. Sample app: 

<dependencies>
    <dependency>
        <groupId>com.yahoo.vespa</groupId>
        <artifactId>documentapi</artifactId>
        <version>7.168.4</version> <!-- Find latest version at search.maven.org/search?q=g:com.yahoo.vespa%20a:documentapi -->
    </dependency>
    <dependency> <!-- ToDo: remove this once ImmutableList is removed -->
        <groupId>>com.google.guava</groupId>
        <artifactId>guava</artifactId>
        <version>28.2-jre</version>
    </dependency>
<dependencies>

import com.yahoo.document.DataType;
import com.yahoo.document.Document;
import com.yahoo.document.DocumentId;
import com.yahoo.document.DocumentPut;
import com.yahoo.document.DocumentType;
import com.yahoo.document.DocumentUpdate;
import com.yahoo.document.datatypes.StringFieldValue;
import com.yahoo.document.datatypes.WeightedSet;
import com.yahoo.document.update.FieldUpdate;
import com.yahoo.documentapi.DocumentAccess;
import com.yahoo.documentapi.SyncParameters;
import com.yahoo.documentapi.SyncSession;

public class DocClient {

    public static void main(String[] args) {

        DocumentAccess access = DocumentAccess.createDefault();
        DocumentType type = access.getDocumentTypeManager().getDocumentType("music");
        DocumentId id = new DocumentId("id:namespace:music::0");
        Document docIn = new Document(type, id);
        SyncSession session = access.createSyncSession(new SyncParameters.Builder().build());

        // Put document with a1,1
        WeightedSet<StringFieldValue> wset = new WeightedSet<>(DataType.getWeightedSet(DataType.STRING));
        wset.put(new StringFieldValue("a1"), 1);
        docIn.setFieldValue("aWeightedset", wset);
        DocumentPut put = new DocumentPut(docIn);
        System.out.println(docIn.toJson());
        session.put(put);

        // Update document with a1,10 and a2,20
        DocumentUpdate upd1 = new DocumentUpdate(type, id);
        WeightedSet<StringFieldValue> wset1 = new WeightedSet<>(DataType.getWeightedSet(DataType.STRING));
        wset1.put(new StringFieldValue("a1"), 10);
        wset1.put(new StringFieldValue("a2"), 20);
        upd1.addFieldUpdate(FieldUpdate.createAddAll(type.getField("aWeightedset"), wset1));
        System.out.println(upd1.toString());
        session.update(upd1);

        Document docOut = session.get(id);
        System.out.println("document get:" + docOut.toJson());

        session.destroy();
        access.shutdown();
    }
}
To test using the sample apps, enable more ports for client to connect to config server and other processes on localhost - change docker command: 
$ docker run --detach --name vespa --hostname localhost --privileged \
  --volume $VESPA_SAMPLE_APPS:/vespa-sample-apps --publish 8080:8080 \
  --publish 19070:19070 --publish 19071:19071 --publish 19090:19090 --publish 19099:19099 --publish 19101:19101 --publish 19112:19112 \
  vespaengine/vespa

Fields

Examples: 

doc.setFieldValue("aByte", (byte)1);
doc.setFieldValue("aInt", (int)1);
doc.setFieldValue("aLong", (long)1);
doc.setFieldValue("aFloat", 1.0);
doc.setFieldValue("aDouble", 1.0);
doc.setFieldValue("aBool", new BoolFieldValue(true));
doc.setFieldValue("aString", "Hello Field!");

doc.setFieldValue("unknownField", "Will not see me!");

Array<IntegerFieldValue> intArray = new Array<>(doc.getField("aArray").getDataType());
intArray.add(new IntegerFieldValue(11));
intArray.add(new IntegerFieldValue(12));
doc.setFieldValue("aArray", intArray);

Struct pos = PositionDataType.valueOf(1,2);
       pos = PositionDataType.fromString("N0.000002;E0.000001");  // two ways to set same value
doc.setFieldValue("aPosition", pos);

doc.setFieldValue("aPredicate", new PredicateFieldValue("aLong in [10..20]"));

byte[] rawBytes = new byte[100];
for (int i = 0; i < rawBytes.length; i++) {
    rawBytes[i] = (byte)i;
}
doc.setFieldValue("aRaw", new Raw(ByteBuffer.wrap(rawBytes)));

Tensor tensor = Tensor.Builder.of(TensorType.fromSpec("tensor<float>>(x[2],y[2])")).
        cell().label("x", 0).label("y", 0).value(1.0).
        cell().label("x", 0).label("y", 1).value(2.0).
        cell().label("x", 1).label("y", 0).value(3.0).
        cell().label("x", 1).label("y", 1).value(5.0).build();
doc.setFieldValue("aTensor", new TensorFieldValue(tensor));

MapFieldValue<StringFieldValue, StringFieldValue> map = new MapFieldValue<>(new MapDataType(DataType.STRING, DataType.STRING));
map.put(new StringFieldValue("key1"), new StringFieldValue("foo"));
map.put(new StringFieldValue("key2"), new StringFieldValue("bar"));
doc.setFieldValue("aMap", map);

WeightedSet<StringFieldValue> wset = new WeightedSet<>(DataType.getWeightedSet(DataType.STRING));
wset.put(new StringFieldValue("strval 1"), 5);
wset.put(new StringFieldValue("strval 2"), 10);
doc.setFieldValue("aWeightedset", wset);

Document updates

A document update is a request to modify a document. See writing to Vespa for update operations.

Primitive, and some multivalue fields (WeightedSet and Array<primitive>), are updated using a FieldUpdate.

Complex, multivalue fields like Map and Array<struct> are updated using AddFieldPathUpdate, AssignFieldPathUpdate and RemoveFieldPathUpdate. Field path updates are only supported on non-attribute fields, index fields, or fields containing struct field attributes. If a field is both an index field and an attribute, then the document is updated in the document store, the index is updated, but the attribute is not updated. Thus you can get old values in document summary requests and old values being used in ranking and grouping. A field path string identifies fields to update - example: 

upd.addFieldPathUpdate(new AssignFieldPathUpdate(type, "myMap{key2}", new StringFieldValue("abc")));
FieldUpdate examples: 
// Simple assignment
Field intField = type.getField("aInt");
IntegerFieldValue intFieldValue = new IntegerFieldValue(2);
FieldUpdate assignUpdate = FieldUpdate.createAssign(intField, intFieldValue);
upd.addFieldUpdate(assignUpdate);

// Arithmetic
FieldUpdate addUpdate = FieldUpdate.createIncrement(type.getField("aLong"), 3);
upd.addFieldUpdate(addUpdate);

// Composite - add one array element
upd.addFieldUpdate(FieldUpdate.createAdd(type.getField("aArray"),
        new IntegerFieldValue(13)));

// Composite - add two array elements
upd.addFieldUpdate(FieldUpdate.createAddAll(type.getField("aArray"),
        List.of(new IntegerFieldValue(14), new IntegerFieldValue(15))));

// Composite - add weightedset element
upd.addFieldUpdate(FieldUpdate.createAdd(type.getField("aWeightedset"),
        new StringFieldValue("add_me"),101));

// Composite - add set to set
WeightedSet wset = new WeightedSet<>(DataType.getWeightedSet(DataType.STRING));
wset.put(new StringFieldValue("a1"), 3);
wset.put(new StringFieldValue("a2"), 4);
upd.addFieldUpdate(FieldUpdate.createAddAll(type.getField("aWeightedset"), wset));

// Composite - update array element
upd.addFieldUpdate(FieldUpdate.createMap(type.getField("aArray"),
        new IntegerFieldValue(1), // array index
        new AssignValueUpdate(new IntegerFieldValue(2))));  // value at index

// Composite - increment weight
upd3.addFieldUpdate(FieldUpdate.createIncrement(type.getField("aWeightedset"),
        new StringFieldValue("a1"), 1));

// DO NOT USE - createMap can cause crash / missing updates TODO FIXME
upd.addFieldUpdate(FieldUpdate.createMap(type.getField("aWeightedset"),
        new StringFieldValue("element1"), // value
        new AssignValueUpdate(new IntegerFieldValue(30))));
FieldPathUpdate examples: 
// Add an element to a map
Array stringArray = new Array(DataType.getArray(DataType.STRING));
stringArray.add(new StringFieldValue("my-val"));
AddFieldPathUpdate addElement = new AddFieldPathUpdate(type, "aMap{key1}", stringArray);
upd.addFieldPathUpdate(addElement);

// Modify an element in a map
upd.addFieldPathUpdate(new AssignFieldPathUpdate(type, "aMap{key2}", new StringFieldValue("abc")));

Update reply semantics

Sending in an update for which the system can not find a corresponding document to update is not considered an error. These are returned with a successful status code (assuming that no actual error occurred during the update processing). Use UpdateDocumentReply.wasFound() to check if the update was known to have been applied.

If the update returns with an error reply, the update may or may not have been applied, depending on where in the platform stack the error occurred.

Document Access

The starting point of for passing documents and updates to Vespa is the DocumentAccess class. This is a singleton (see get() method) session factory (see createXSession() methods), that provides three distinct access types:

  • Synchronous random access: provided by the class SyncSession. Suitable for low-throughput proof-of-concept applications.
  • Asynchronous random access: provided by the class AsyncSession. It allows for document repository writes and random access with high throughput.
  • Visiting: provided by the class VisitorSession. Allows a set of documents to be accessed in order decided by the document repository, which gives higher read throughput than random access.

AsyncSession

This class represents a session for asynchronous access to a document repository. It is created by calling myDocumentAccess.createAsyncSession(myAsyncSessionParams), and provides document repository writes and random access with high throughput. The usage pattern for an asynchronous session is like:

  1. put(), update(), get() or remove() is invoked on the session, and it returns a synchronous Result object that indicates whether or not the request was successful. The Result object also contains a request identifier.
  2. The client polls the session for a Response through its getNext() method. Any operation accepted by an asynchronous session will produce exactly one response within the configured timeout.
  3. Once a response is available, it is matched to the request by inspecting the response's request identifier. The response may also contain data, either a retrieved document or a failed document put or update that needs to be handled.
  4. Note that the client must process the response queue or your JVM will run into garabage collection issues as the underlying session keeps track of all responses and unless they are consumed they will be kept alive and not be gc'ed.
Example: 

import com.yahoo.document.*;
import com.yahoo.documentapi.*;

public class MyClient {

    private final DocumentAccess access = DocumentAccess.createDefault();
    private final AsyncSession session = access.createAsyncSession(new AsyncParameters());
    private boolean abort = false;
    private int numPending = 0;

    /**
     * Implements application entry point.
     *
     * @param args Command line arguments.
     */
    public static void main(String[] args) {
        MyClient app = null;
        try {
            app = new MyClient();
            app.run();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (app != null) {
                app.shutdown();
            }
        }
        if (app == null || app.abort) {
            System.exit(1);
        }
    }

    /**
     * This is the main entry point of the client. This method will not return until all available documents
     * have been fed and their responses have been returned, or something signaled an abort.
     */
    public void run() {
        System.out.println("client started");
        while (!abort) {
            flushResponseQueue();

            Document doc = getNextDocument();
            if (doc == null) {
                System.out.println("no more documents to put");
                break;
            }
            System.out.println("sending doc " + doc);

            while (!abort) {
                Result res = session.put(doc);
                if (res.isSuccess()) {
                    System.out.println("put has request id " + res.getRequestId());
                    ++numPending;
                    break; // step to next doc.
                } else if (res.getType() == Result.ResultType.TRANSIENT_ERROR) {
                    System.out.println("send queue full, waiting for some response");
                    processNext(9999);
                } else {
                    res.getError().printStackTrace();
                    abort = true; // this is a fatal error
                }
            }
        }
        if (!abort) {
            waitForPending();
        }
        System.out.println("client stopped");
    }

    /**
     * Shutdown the underlying api objects.
     */
    public void shutdown() {
        System.out.println("shutting down document api");
        session.destroy();
        access.shutdown();
    }

    /**
     * Returns the next document to feed to Vespa. This method should only return null when the end of the
     * document stream has been reached, as returning null terminates the client. This is the point at which
     * your application logic should block if it knows more documents will eventually become available.
     *
     * @return The next document to put, or null to terminate.
     */
    public Document getNextDocument() {
        return null; // TODO: Implement at your discretion.
    }

    /**
     * Processes all immediately available responses.
     */
    void flushResponseQueue() {
        System.out.println("flushing response queue");
        while (processNext(0)) {
            // empty
        }
    }

    /**
     * Wait indefinitely for the responses of all sent operations to return. This method will only return
     * early if the abort flag is set.
     */
    void waitForPending() {
        while (numPending != 0) {
            if (abort) {
                System.out.println("waiting aborted, " + numPending + " still pending");
                break;
            }
            System.out.println("waiting for " + numPending + " responses");
            processNext(9999);
        }
    }

    /**
     * Retrieves and processes the next response available from the underlying asynchronous session. If no
     * response becomes available within the given timeout, this method returns false.
     *
     * @param timeout The maximum number of seconds to wait for a response.
     * @return True if a response was processed, false otherwise.
     */
    boolean processNext(int timeout) {
        Response res;
        try {
            res = session.getNext(timeout);
        } catch (InterruptedException e) {
            e.printStackTrace();
            abort = true;
            return false;
        }
        if (res == null) {
            return false;
        }
        System.out.println("got response for request id " + res.getRequestId());
        --numPending;
        if (!res.isSuccess()) {
            System.err.println(res.getTextMessage());
            abort = true;
            return false;
        }
        return true;
    }
}

VisitorSession

This class represents a session for sequentially visiting documents with high throughput.

A visitor is started when creating the VisitorSession through a call to createVisitorSession. A visitor target, that is a receiver of visitor data, can be created through a call to createVisitorDestinationSession. The VisitorSession is a receiver of visitor data. See visiting reference for details. The VisitorSession:

  • Controls the operation of the visiting process
  • Handles the data resulting from visiting data in the system
Those two different tasks may be set up to be handled by a VisitorControlHandler and a VisitorDataHandler respectively. These handlers may be supplied to the VisitorSession in the VisitorParameters object, together with a set of other parameters for visiting. Example: To increase performance, let more separate visitor destinations handle visitor data - then specify the addresses to remote data handlers.

The default VisitorDataHandler used by the VisitorSession returned from DocumentAccess is VisitorDataQueue which queues up incoming documents and implements a polling API. The documents can be extracted by calls to the session's getNext() methods and can be ack-ed by the ack() method. The default VisitorControlHandler can be accessed through the session's getProgress(), isDone(), and waitUntilDone() methods.

Implement custom VisitorControlHandler and VisitorDataHandler by subclassing them and supplying these to the VisitorParameters object.

The VisitorParameters object controls how and what data will be visited - refer to the javadoc. Configure the document selection string to select what data to visit - the default is all data.

For improved performance, dump a subset of the document fields - control which fields are returned by using fieldSet - see Document field sets.

Example: 

import com.yahoo.document.Document;
import com.yahoo.document.DocumentId;
import com.yahoo.documentapi.DocumentAccess;
import com.yahoo.documentapi.DumpVisitorDataHandler;
import com.yahoo.documentapi.ProgressToken;
import com.yahoo.documentapi.VisitorControlHandler;
import com.yahoo.documentapi.VisitorParameters;
import com.yahoo.documentapi.VisitorSession;

import java.util.concurrent.TimeoutException;

public class MyClient {

    public static void main(String[] args) throws Exception {
        VisitorParameters params = new VisitorParameters("true");
        params.setLocalDataHandler(new DumpVisitorDataHandler() {

            @Override
            public void onDocument(Document doc, long timeStamp) {
                System.out.print(doc.toXML(""));
            }

            @Override
            public void onRemove(DocumentId id) {
                System.out.println("id=" + id);
            }
        });
        params.setControlHandler(new VisitorControlHandler() {

            @Override
            public void onProgress(ProgressToken token) {
                System.err.format("%.1f %% finished.\n", token.percentFinished());
                super.onProgress(token);
            }

            @Override
            public void onDone(CompletionCode code, String message) {
                System.err.println("Completed visitation, code " + code + ": " + message);
                super.onDone(code, message);
            }
        });
        params.setRoute(args.length > 0 ? args[0] : "[Storage:cluster=storage;clusterconfigid=storage]");
        params.setFieldSet(args.length > 1 ? args[1] : "[all]");

        DocumentAccess access = DocumentAccess.createDefault();
        VisitorSession session = access.createVisitorSession(params);
        if (!session.waitUntilDone(0)) {
            throw new TimeoutException();
        }
        session.destroy();
        access.shutdown();
    }
}
The first optional argument to this client is the route of the cluster to visit. The second is the fieldset set to retrieve.