org.rocksdb

Class HashLinkedListMemTableConfig

java.lang.Object

org.rocksdb.MemTableConfig

org.rocksdb.HashLinkedListMemTableConfig

public class HashLinkedListMemTableConfig
extends MemTableConfig

The config for hash linked list memtable representation Such memtable contains a fix-sized array of buckets, where each bucket points to a sorted singly-linked list (or null if the bucket is empty). Note that since this mem-table representation relies on the key prefix, it is required to invoke one of the usePrefixExtractor functions to specify how to extract key prefix given a key. If proper prefix-extractor is not set, then RocksDB will use the default memtable representation (SkipList) instead and post a warning in the LOG.

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAUL_THRESHOLD_USE_SKIPLIST
static long	DEFAULT_BUCKET_COUNT
static int	DEFAULT_BUCKET_ENTRIES_LOG_THRES
static long	DEFAULT_HUGE_PAGE_TLB_SIZE
static boolean	DEFAULT_IF_LOG_BUCKET_DIST_WHEN_FLUSH

Constructor Summary

Constructors

Constructor and Description
HashLinkedListMemTableConfig() HashLinkedListMemTableConfig constructor

Method Summary

Methods

Modifier and Type	Method and Description
long	bucketCount() Returns the number of buckets that will be used in the memtable created based on this config.
int	bucketEntriesLoggingThreshold() Returns the maximum number of entries in one bucket before logging starts.
long	hugePageTlbSize() Returns the size value of hugePageTlbSize.
boolean	ifLogBucketDistWhenFlush() Returns information about logging the distribution of number of entries on flush.
protected long	newMemTableFactoryHandle() This function should only be called by Options.setMemTableConfig(), which will create a c++ shared-pointer to the c++ MemTableRepFactory that associated with the Java MemTableConfig.
HashLinkedListMemTableConfig	setBucketCount(long count) Set the number of buckets in the fixed-size array used in the hash linked-list mem-table.
HashLinkedListMemTableConfig	setBucketEntriesLoggingThreshold(int threshold) If number of entries in one bucket exceeds that setting, log about it.
HashLinkedListMemTableConfig	setHugePageTlbSize(long size) Set the size of huge tlb or allocate the hashtable bytes from malloc if size <= 0.
HashLinkedListMemTableConfig	setIfLogBucketDistWhenFlush(boolean logDistribution) If true the distrubition of number of entries will be logged.
HashLinkedListMemTableConfig	setThresholdUseSkiplist(int threshold) Set maximum number of entries in one bucket.
int	thresholdUseSkiplist() Returns entries per bucket threshold before LinkedList is replaced by SkipList usage for that bucket.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_BUCKET_COUNT

public static final long DEFAULT_BUCKET_COUNT

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Constant Field Values

DEFAULT_HUGE_PAGE_TLB_SIZE

public static final long DEFAULT_HUGE_PAGE_TLB_SIZE

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Constant Field Values

DEFAULT_BUCKET_ENTRIES_LOG_THRES

public static final int DEFAULT_BUCKET_ENTRIES_LOG_THRES

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Constant Field Values

DEFAULT_IF_LOG_BUCKET_DIST_WHEN_FLUSH

public static final boolean DEFAULT_IF_LOG_BUCKET_DIST_WHEN_FLUSH

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Constant Field Values

DEFAUL_THRESHOLD_USE_SKIPLIST

public static final int DEFAUL_THRESHOLD_USE_SKIPLIST

See Also:

Constant Field Values

Constructor Detail

HashLinkedListMemTableConfig

public HashLinkedListMemTableConfig()

HashLinkedListMemTableConfig constructor

Method Detail

setBucketCount

public HashLinkedListMemTableConfig setBucketCount(long count)

Set the number of buckets in the fixed-size array used in the hash linked-list mem-table.

Parameters:

count - the number of hash buckets.

Returns:

the reference to the current HashLinkedListMemTableConfig.

bucketCount

public long bucketCount()

Returns the number of buckets that will be used in the memtable created based on this config.

Returns:

the number of buckets

setHugePageTlbSize

public HashLinkedListMemTableConfig setHugePageTlbSize(long size)

Set the size of huge tlb or allocate the hashtable bytes from malloc if size <= 0.

The user needs to reserve huge pages for it to be allocated, like: sysctl -w vm.nr_hugepages=20

See linux documentation/vm/hugetlbpage.txt

Parameters:

size - if set to <= 0 hashtable bytes from malloc

Returns:

the reference to the current HashLinkedListMemTableConfig.

hugePageTlbSize

public long hugePageTlbSize()

Returns the size value of hugePageTlbSize.

Returns:

the hugePageTlbSize.

setBucketEntriesLoggingThreshold

public HashLinkedListMemTableConfig setBucketEntriesLoggingThreshold(int threshold)

If number of entries in one bucket exceeds that setting, log about it.

Parameters:

threshold - - number of entries in a single bucket before logging starts.

Returns:

the reference to the current HashLinkedListMemTableConfig.

bucketEntriesLoggingThreshold

public int bucketEntriesLoggingThreshold()

Returns the maximum number of entries in one bucket before logging starts.

Returns:

maximum number of entries in one bucket before logging starts.

setIfLogBucketDistWhenFlush

public HashLinkedListMemTableConfig setIfLogBucketDistWhenFlush(boolean logDistribution)

If true the distrubition of number of entries will be logged.

Parameters:

logDistribution - - boolean parameter indicating if number of entry distribution shall be logged.

Returns:

the reference to the current HashLinkedListMemTableConfig.

ifLogBucketDistWhenFlush

public boolean ifLogBucketDistWhenFlush()

Returns information about logging the distribution of number of entries on flush.

Returns:

if distrubtion of number of entries shall be logged.

setThresholdUseSkiplist

public HashLinkedListMemTableConfig setThresholdUseSkiplist(int threshold)

Set maximum number of entries in one bucket. Exceeding this val leads to a switch from LinkedList to SkipList.

Parameters:

threshold - maximum number of entries before SkipList is used.

Returns:

the reference to the current HashLinkedListMemTableConfig.

thresholdUseSkiplist

public int thresholdUseSkiplist()

Returns entries per bucket threshold before LinkedList is replaced by SkipList usage for that bucket.

Returns:

entries per bucket threshold before SkipList is used.

newMemTableFactoryHandle

protected long newMemTableFactoryHandle()

Description copied from class: MemTableConfig

This function should only be called by Options.setMemTableConfig(), which will create a c++ shared-pointer to the c++ MemTableRepFactory that associated with the Java MemTableConfig.

Specified by:

newMemTableFactoryHandle in class MemTableConfig

Returns:

native handle address to native memory table instance.

See Also:

Options.setMemTableConfig(MemTableConfig)