com.hazelcast.map.impl.query

Class QueryResultSizeLimiter

java.lang.Object

com.hazelcast.map.impl.query.QueryResultSizeLimiter

public class QueryResultSizeLimiter
extends Object

Responsible for limiting result size of queries.

This class defines a hard coded minimum MINIMUM_MAX_RESULT_LIMIT as well as a factor MAX_RESULT_LIMIT_FACTOR to ensure that the actual result size limit will be a reasonable value. Due to the used hash algorithm the data of a map is not distributed equally on all partitions in the cluster. Since the decision whether of not the QueryResultSizeExceededException is thrown is made on the local number of partition entries, we need a reliable distribution of data. The goal is to prevent false positives, since those might surprise the user. So the exception should never been thrown below the configured limit.

The minimum value of 100000 and the factor of 1.149999976158142f were determined by testing on which limit the exception was thrown with different map key types.

Field Summary

Fields

Modifier and Type	Field and Description
static float	MAX_RESULT_LIMIT_FACTOR Adds a security margin to the configured result size limit to prevent false positives.
static float	MAX_RESULT_LIMIT_FACTOR_FOR_PRECHECK Adds a security margin to the configured result size limit to prevent false positives in pre-check.
static int	MINIMUM_MAX_RESULT_LIMIT Defines the minimum value for the result size limit to ensure a sufficient distribution of data in the partitions.

Constructor Summary

Constructors

Constructor and Description
QueryResultSizeLimiter(MapServiceContext mapServiceContext, ILogger logger)

Method Summary

Modifier and Type	Method and Description
boolean	isPreCheckEnabled() Just for testing.
boolean	isQueryResultLimitEnabled() Just for testing.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

MINIMUM_MAX_RESULT_LIMIT

public static final int MINIMUM_MAX_RESULT_LIMIT

Defines the minimum value for the result size limit to ensure a sufficient distribution of data in the partitions.

See Also:

QueryResultSizeLimiter, Constant Field Values

MAX_RESULT_LIMIT_FACTOR

public static final float MAX_RESULT_LIMIT_FACTOR

Adds a security margin to the configured result size limit to prevent false positives.

See Also:

QueryResultSizeLimiter, Constant Field Values

MAX_RESULT_LIMIT_FACTOR_FOR_PRECHECK

public static final float MAX_RESULT_LIMIT_FACTOR_FOR_PRECHECK

Adds a security margin to the configured result size limit to prevent false positives in pre-check. Required since the precheck takes 3 partitions by default and their size may vary due to data distr. imbalance.

See Also:

QueryResultSizeLimiter, Constant Field Values

Constructor Detail

QueryResultSizeLimiter

public QueryResultSizeLimiter(MapServiceContext mapServiceContext,
                              ILogger logger)

Method Detail

isQueryResultLimitEnabled

public boolean isQueryResultLimitEnabled()

Just for testing.

isPreCheckEnabled

public boolean isPreCheckEnabled()

Just for testing.