Package org.apache.cassandra.db.compaction

Interface ShardManager

All Known Implementing Classes:

ShardManagerDiskAware, ShardManagerNoDisks, ShardManagerTrivial

public interface ShardManager

Field Summary

Fields

Modifier and Type	Field	Description
static double	MINIMUM_TOKEN_COVERAGE	Single-partition, and generally sstables with very few partitions, can cover very small sections of the token space, resulting in very high densities.

Method Summary

Modifier and Type	Method	Description
ShardTracker	boundaries(int shardCount)	Construct a boundary/shard iterator for the given number of shards.
default double	calculateCombinedDensity(java.util.Set<? extends SSTableReader> sstables)	Estimate the density of the sstable that will be the result of compacting the given sources.
default int	compareByDensity(SSTableReader a, SSTableReader b)
static Range<Token>	coveringRange(PartitionPosition first, PartitionPosition last)
static Range<Token>	coveringRange(SSTableReader sstable)
static ShardManager	create(ColumnFamilyStore cfs)
default double	density(SSTableReader rdr)	Return the density of an SSTable, i.e.
boolean	isOutOfDate(long ringVersion)
double	localSpaceCoverage()	The total fraction of the token space covered by the local ranges.
default double	rangeSpanned(PartitionPosition first, PartitionPosition last)
double	rangeSpanned(Range<Token> tableRange)	The token range fraction spanned by the given range, adjusted for the local range ownership.
default double	rangeSpanned(SSTableReader rdr)	Return the token space share that the given SSTable spans, excluding any non-locally owned space.
double	shardSetCoverage()	The fraction of the token space covered by a shard set, i.e.

Field Detail

MINIMUM_TOKEN_COVERAGE

static final double MINIMUM_TOKEN_COVERAGE

Single-partition, and generally sstables with very few partitions, can cover very small sections of the token space, resulting in very high densities. Additionally, sstables that have completely fallen outside of the local token ranges will end up with a zero coverage. To avoid problems with both we check if coverage is below the minimum, and replace it with 1.

Method Detail

create

static ShardManager create(ColumnFamilyStore cfs)

isOutOfDate

boolean isOutOfDate(long ringVersion)

rangeSpanned

double rangeSpanned(Range<Token> tableRange)

The token range fraction spanned by the given range, adjusted for the local range ownership.

localSpaceCoverage

double localSpaceCoverage()

The total fraction of the token space covered by the local ranges.

shardSetCoverage

double shardSetCoverage()

The fraction of the token space covered by a shard set, i.e. the space that is split in the requested number of shards. If no disks are defined, this is the same as localSpaceCoverage(). Otherwise, it is the token coverage of a disk.

boundaries

ShardTracker boundaries(int shardCount)

Construct a boundary/shard iterator for the given number of shards. Note: This does not offer a method of listing the shard boundaries it generates, just to advance to the corresponding one for a given token. The only usage for listing is currently in tests. Should a need for this arise, see CompactionSimulationTest for a possible implementation.

coveringRange

static Range<Token> coveringRange(SSTableReader sstable)

coveringRange

static Range<Token> coveringRange(PartitionPosition first,
                                  PartitionPosition last)

rangeSpanned

default double rangeSpanned(SSTableReader rdr)

Return the token space share that the given SSTable spans, excluding any non-locally owned space. Returns a positive floating-point number between 0 and 1.

rangeSpanned

default double rangeSpanned(PartitionPosition first,
                            PartitionPosition last)

density

default double density(SSTableReader rdr)

Return the density of an SSTable, i.e. its size divided by the covered token space share. This is an improved measure of the compaction age of an SSTable that grows both with STCS-like full-SSTable compactions (where size grows, share is constant), LCS-like size-threshold splitting (where size is constant but share shrinks), UCS-like compactions (where size may grow and covered shards i.e. share may decrease) and can reproduce levelling structure that corresponds to all, including their mixtures.

compareByDensity

default int compareByDensity(SSTableReader a,
                             SSTableReader b)

calculateCombinedDensity

default double calculateCombinedDensity(java.util.Set<? extends SSTableReader> sstables)

Estimate the density of the sstable that will be the result of compacting the given sources.