Module org.evrete.core
Package org.evrete.api.spi

Interface ValueIndexer<V>

Type Parameters:
V - The type of values stored in the collection.
public interface ValueIndexer<V>
A collection that stores values and assigns them a unique long identifier. The engine uses this API to store fact field values expressed as Object[].

Aside from hashing and equality, the default implementation of this interface essentially works as shown below: 


 private final AtomicLong indexer = new AtomicLong(0);
 private final Map<Object[], Long> mapping = new ConcurrentHashMap<>();
 private final Map<Long, Object[]> reverse = new ConcurrentHashMap<>();

 public long getOrCreateId(Object[] fieldValues) {
     return mapping.computeIfAbsent(fieldValues, k -> {
         long id = indexer.getAndIncrement();
         reverse.put(id, k);
         return id;
     });
 }

When a RuleSession is created, the engine will generate as many instances of this interface as there are logical types in the ruleset. The implementations must be thread-safe.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    assignId(long id, V value)
    Assigns the given value to the specified identifier.
    void
    clear()
    Clears the internally stored mapping.
    V
    delete(long id)
    Deletes the value associated with the given unique identifier.
    V
    get(long id)
    Retrieves the value associated with the given unique identifier.
    long
    getOrCreateId(V value)
    Returns the unique identifier for the specified value, creating a new one if it does not already exist.

  • Method Details

    • getOrCreateId

      long getOrCreateId(V value)
      Returns the unique identifier for the specified value, creating a new one if it does not already exist.
      Parameters:
      value - The value for which the identifier is to be retrieved or created.
      Returns:
      The unique long identifier assigned to the specified value.

    • get

      V get(long id)
      Retrieves the value associated with the given unique identifier.
      Parameters:
      id - The unique identifier for the desired value.
      Returns:
      The value associated with the specified identifier, or null if no such value exists.

    • delete

      V delete(long id)
      Deletes the value associated with the given unique identifier.
      Parameters:
      id - The unique identifier for the value to be deleted.
      Returns:
      The value that was associated with the specified identifier, or null if no such value exists.

    • assignId

      void assignId(long id, V value)
      Assigns the given value to the specified identifier.
      Parameters:
      id - The unique identifier for the value.
      value - The value to be associated with the specified identifier.

    • clear

      void clear()
      Clears the internally stored mapping.