com.gigaspaces.client.iterator

Enum SpaceIteratorType

java.lang.Object

java.lang.Enum<SpaceIteratorType>

com.gigaspaces.client.iterator.SpaceIteratorType

All Implemented Interfaces:

Serializable, Comparable<SpaceIteratorType>

public enum SpaceIteratorType
extends Enum<SpaceIteratorType>

Enum of SpaceIterator implementation types

Since:

15.2.0

Author:

Alon Shoham

Enum Constant Summary

Enum Constants

Enum Constant and Description
CURSOR This type iterates over entries by maintaining an iterator within each partition (similar to database cursors).
PREFETCH_UIDS This type iterates over entries by first fetching all matching entries UIDs, then fetching the actual entries in batches by uids.

Method Summary

Modifier and Type	Method and Description
static SpaceIteratorType	valueOf(String name) Returns the enum constant of this type with the specified name.
static SpaceIteratorType[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

CURSOR

public static final SpaceIteratorType CURSOR

This type iterates over entries by maintaining an iterator within each partition (similar to database cursors). Since getting entries one-by-one is extremely inefficient, this iterator offers the following optimizations: In theory, each hasNext() invocation would require at least one remote call, which would be extremely inefficient. In practice, the iterator uses the following techniques to improve performance: 1. The server-side iterator returns a batch of entries instead of a single one. That batch is used implicitly to optimize hasNext()/next(). Users can control the batch size using SpaceIteratorConfiguration.setBatchSize(). 2. When the iterator is initialized, it asynchronously requests a batch from all partitions. That means that once any of the partitions returns a result, the iterator can start serving entries. It also means that once that batch is consumed, the iterator can continue serving entries from other partitions batches which meanwhile arrived. 3. When the iterator starts consuming entries from a partition batch, it implicitly sends an asynchronous request in the background to that partition for the next batch, which further reduces the time waiting for entries. With each partition batch consumption, the next batch is fetched in the background from that specific partition Advantages (compared to PREFETCH_UIDS): 1. Short latency till first entry is served (independent of number of matching entries). 2. Small memory footprint on client side (independent of number of matching entries). 3. Small workload on space: single batch is fetched from each partition on any given time Disadvantages: 1. Intolerant for primary-backup failover in a partition: If a primary space fails, entries will not be fetched from that partition. Iterator will continue to serve entries from other partitions.

PREFETCH_UIDS

public static final SpaceIteratorType PREFETCH_UIDS

This type iterates over entries by first fetching all matching entries UIDs, then fetching the actual entries in batches by uids. Advantages (compared to CURSOR): 1. Tolerant to primary space failure in any partition Disadvantages: 1. Long latency till first entry is served (independent of number of matching entries). 2. Large memory footprint on client side (independent of number of matching entries). 3. Large workload on space: all template matching entries need to be gathered on init

Method Detail

values

public static SpaceIteratorType[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (SpaceIteratorType c : SpaceIteratorType.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static SpaceIteratorType valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null