Data Structures Reference

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    You can use complex data structures such as dictionaries and lists in Couchbase.

    Data structures in Couchbase are similar in concept to data structures in the Java Collections Framework:

    See our Data Model pages.

    Here is a list of common operations:

    Table 1. Data Structure Operations

    mapAdd

    Add a key to the map.

    map.put("some_key", "value");

    mapRemove

    Remove a key from a map.

    map.remove("some_key");

    mapGet

    Get an item from a map.

    map.get("some_key"); //=> value

    If the key is not found, a PathNotFoundException is raised.

    listAppend

    Add an item to the end of a list.

    arrayList.add(1234);

    listPrepend

    Add an item to the beginning of a list.

    arrayList.add(0, "hello world");

    listRemove

    Remove a value from a list.

    arrayList.remove(1);

    listSet

    Set an element at a specific index in the list.

    arrayList.set(0, "first value");

    listGet

    Get an item from a list by its index.

    arrayList.get(0);

    If the index is out of range, a PathNotFoundException will be thrown. Note that you can get the last array element by specifying -1 as the index.

    setAdd

    Add an item to a set, if the item does not yet exist in the set.

    arraySet.add("some_value");

    Note that a set is just a list. You can retrieve the entire set by simply using a full-document get operation:

    Set set = arraySet;
    Currently, you can only store primitive values in sets, such as strings, ints, and booleans.

    setContains

    Check if a value exists in the set.

    arraySet.contains("value");

    setRemove

    Remove an item from a set, if it exists. An exception is not thrown if the item does not exist. You can determine if an item existed or not by the return value. If the item did not exist beforehand, null is returned.

    arraySet.remove("some_value");

    queuePush

    Add an item to the beginning of the queue.

    queue.add("job123");

    Note that a queue is just a list. You can retrieve items from the middle of the queue by using listGet

    queuePop

    Remove an item from the end of the queue and return it.

    Object item = queue.poll(); //=> "job123"

    If the queue is empty, then null is returned.

    mapSize, listSize, setSize, queueSize

    These methods get the length of the data structure. For maps, this is the number of key-value pairs inside the map. For lists, queues, and sets, this is the number of elements in the structure.

    int len = arrayList.size(); //=> 42

    Note that there are only two basic types: map and list. Types such as queue and set are merely derivatives of list.

    Data Structures and Key-Value APIs

    Data structures can be accessed using key-value APIs as well. In fact, the data structure API is actually a client-side wrapper around the key-value and sub-document API. Most of the data structure APIs wrap the sub-document API directly.

    Because the data structure API is just a wrapper around the various key-value APIs, you are free to switch between them in your code.

    Collections Framework Integration

    In addition to the Bucket level methods for working with data structures, the Java SDK provides implementations of the Map, List, Set, and Queue interfaces from the Java Collections Framework. Instead of maintaining in-memory storage, these implementations are backed by JSON documents stored in Couchbase Server. The implementations are thread-safe and suitable for concurrent use. The Map, List, and Queue implementations may contain values of the following types:

    • String

    • Integer

    • Long

    • Double

    • Boolean

    • BigInteger

    • BigDecimal

    • JsonObject

    • JsonArray

    The Set implementation may contain values of all of the above types except JsonObject and JsonArray.

    CouchbaseMap

    The CouchbaseMap<V> class implements Map<String, V>. It allows null values, but does not allow null keys.

    Example usage:

    Map<String, String> favorites = new CouchbaseMap<String>("mapDocId", collection, String.class, MapOptions.mapOptions());
    favorites.put("color", "Blue");
    favorites.put("flavor", "Chocolate");
    
    System.out.println(favorites); //=> {flavor=Chocolate, color=Blue}
    
    // What does the JSON document look like?
    System.out.println(collection.get("mapDocId").contentAsObject());
    //=> {"flavor":"Chocolate","color":"Blue"}

    CouchbaseArrayList

    The CouchbaseArrayList<V> class implements List<V>. It allows null values.

    Example usage:

    List<String> names = new CouchbaseArrayList<String>("listDocId", collection, String.class, ArrayListOptions.arrayListOptions());
    names.add("Alice");
    names.add("Bob");
    names.add("Alice");
    
    System.out.println(names); //=> [Alice, Bob, Alice]
    
    // What does the JSON document look like?
    System.out.println(collection.get("listDocId").contentAsArray());
    //=> ["Alice","Bob","Alice"]

    CouchbaseArraySet

    The CouchbaseArraySet<V> class implements Set<V>. It allows null values.

    Example usage:

    Set<String> uniqueNames = new CouchbaseArraySet<String>("setDocId", collection, String.class, ArraySetOptions.arraySetOptions());
    uniqueNames.add("Alice");
    uniqueNames.add("Bob");
    uniqueNames.add("Alice");
    
    System.out.println(uniqueNames); //=> [Alice, Bob]
    
    // What does the JSON document look like?
    System.out.println(collection.get("setDocId").contentAsArray());
    //=> ["Alice","Bob"]

    CouchbaseQueue

    The CouchbaseQueue<V> class implements Queue<V>. It does not allow null values.

    Example usage:

    Queue<String> shoppingList = new CouchbaseQueue<String>("queueDocId", collection, String.class, QueueOptions.queueOptions());
    shoppingList.add("loaf of bread");
    shoppingList.add("container of milk");
    shoppingList.add("stick of butter");
    
    // What does the JSON document look like?
    System.out.println(collection.get("queueDocId").contentAsArray());
    //=> ["stick of butter","container of milk","loaf of bread"]
    
    String item;
    while ((item = shoppingList.poll()) != null) {
      System.out.println(item);
      // => loaf of bread
      // => container of milk
      // => stick of butter
    }
    
    // What does the JSON document look like after draining the queue?
    System.out.println(collection.get("queueDocId").contentAsArray());
    //=> []