Package 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 Details

    • DEFAULT_BUCKET_COUNT

      public static final long DEFAULT_BUCKET_COUNT
      See Also:

    • DEFAULT_HUGE_PAGE_TLB_SIZE

      public static final long DEFAULT_HUGE_PAGE_TLB_SIZE
      See Also:

    • DEFAULT_BUCKET_ENTRIES_LOG_THRES

      public static final int DEFAULT_BUCKET_ENTRIES_LOG_THRES
      See Also:

    • DEFAULT_IF_LOG_BUCKET_DIST_WHEN_FLUSH

      public static final boolean DEFAULT_IF_LOG_BUCKET_DIST_WHEN_FLUSH
      See Also:

    • DEFAUL_THRESHOLD_USE_SKIPLIST

      public static final int DEFAUL_THRESHOLD_USE_SKIPLIST
      See Also:

  • Constructor Details

    • HashLinkedListMemTableConfig

      public HashLinkedListMemTableConfig()
      HashLinkedListMemTableConfig constructor

  • Method Details

    • 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 distribution 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: