org.apache.lucene.util
Class RamUsageEstimator

java.lang.Object
  org.apache.lucene.util.RamUsageEstimator

public final class RamUsageEstimator
extends Object

Estimates the size of a given Object using a given MemoryModel for primitive size information. Resource Usage: Internally uses a Map to temporally hold a reference to every object seen. If checkInterned, all Strings checked will be interned, but those that were not already interned will be released for GC when the estimate is complete.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Field Summary

static int	NUM_BYTES_ARRAY_HEADER
static int	NUM_BYTES_CHAR
static int	NUM_BYTES_DOUBLE
static int	NUM_BYTES_FLOAT
static int	NUM_BYTES_INT
static int	NUM_BYTES_LONG
static int	NUM_BYTES_OBJECT_HEADER
static int	NUM_BYTES_OBJECT_REF
static int	NUM_BYTES_SHORT

Constructor Summary

RamUsageEstimator()
Constructs this object with an AverageGuessMemoryModel and checkInterned = true.

RamUsageEstimator(boolean checkInterned)

RamUsageEstimator(MemoryModel memoryModel)

RamUsageEstimator(MemoryModel memoryModel, boolean checkInterned)

Method Summary

long	estimateRamUsage(Object obj)
static String	humanReadableUnits(long bytes, DecimalFormat df) Return good default units based on byte size.

Methods inherited from class java.lang.Object

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

Field Detail

NUM_BYTES_SHORT

public static final int NUM_BYTES_SHORT

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Constant Field Values

NUM_BYTES_INT

public static final int NUM_BYTES_INT

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Constant Field Values

NUM_BYTES_LONG

public static final int NUM_BYTES_LONG

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Constant Field Values

NUM_BYTES_FLOAT

public static final int NUM_BYTES_FLOAT

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Constant Field Values

NUM_BYTES_DOUBLE

public static final int NUM_BYTES_DOUBLE

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Constant Field Values

NUM_BYTES_CHAR

public static final int NUM_BYTES_CHAR

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Constant Field Values

NUM_BYTES_OBJECT_HEADER

public static final int NUM_BYTES_OBJECT_HEADER

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Constant Field Values

NUM_BYTES_OBJECT_REF

public static final int NUM_BYTES_OBJECT_REF

NUM_BYTES_ARRAY_HEADER

public static final int NUM_BYTES_ARRAY_HEADER

Constructor Detail

RamUsageEstimator

public RamUsageEstimator()

Constructs this object with an AverageGuessMemoryModel and checkInterned = true.

RamUsageEstimator

public RamUsageEstimator(boolean checkInterned)

Parameters:

checkInterned - check if Strings are interned and don't add to size if they are. Defaults to true but if you know the objects you are checking won't likely contain many interned Strings, it will be faster to turn off intern checking.

RamUsageEstimator

public RamUsageEstimator(MemoryModel memoryModel)

Parameters:

memoryModel - MemoryModel to use for primitive object sizes.

RamUsageEstimator

public RamUsageEstimator(MemoryModel memoryModel,
                         boolean checkInterned)

Parameters:

memoryModel - MemoryModel to use for primitive object sizes.

checkInterned - check if Strings are interned and don't add to size if they are. Defaults to true but if you know the objects you are checking won't likely contain many interned Strings, it will be faster to turn off intern checking.

Method Detail

estimateRamUsage

public long estimateRamUsage(Object obj)

humanReadableUnits

public static String humanReadableUnits(long bytes,
                                        DecimalFormat df)

Return good default units based on byte size.