org.h2.mvstore.db

类 NullValueDataType

java.lang.Object

org.h2.mvstore.db.NullValueDataType

所有已实现的接口:

Comparator<Value>, DataType<Value>

public final class NullValueDataType
extends Object
implements DataType<Value>

Dummy data type used when no value is required. This data type doesn't use any disk space and always returns SQL NULL value.

字段概要

字段

限定符和类型	字段和说明
static NullValueDataType	INSTANCE Dummy data type instance.

方法概要

限定符和类型	方法和说明
int	binarySearch(Value key, Object storage, int size, int initialGuess) Perform binary search for the key within the storage
int	compare(Value a, Value b) Compare two keys.
Value[]	createStorage(int size) Create storage object of array type to hold values
int	getMemory(Value obj) Calculates the amount of used memory in bytes.
boolean	isMemoryEstimationAllowed() Whether memory estimation based on previously seen values is allowed/desirable
Value	read(ByteBuffer buff) Read an object.
void	read(ByteBuffer buff, Object storage, int len) Read a list of objects.
void	write(WriteBuffer buff, Object storage, int len) Write a list of objects.
void	write(WriteBuffer buff, Value obj) Write an object.

从类继承的方法 java.lang.Object

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

从接口继承的方法 java.util.Comparator

comparing, comparing, comparingDouble, comparingInt, comparingLong, equals, naturalOrder, nullsFirst, nullsLast, reversed, reverseOrder, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

字段详细资料

INSTANCE

public static final NullValueDataType INSTANCE

Dummy data type instance.

方法详细资料

compare

public int compare(Value a,
                   Value b)

从接口复制的说明: DataType

Compare two keys.

指定者:

compare 在接口中 Comparator<Value>

指定者:

compare 在接口中 DataType<Value>

参数:

a - the first key

b - the second key

返回:

-1 if the first key is smaller, 1 if larger, and 0 if equal

binarySearch

public int binarySearch(Value key,
                        Object storage,
                        int size,
                        int initialGuess)

从接口复制的说明: DataType

Perform binary search for the key within the storage

指定者:

binarySearch 在接口中 DataType<Value>

参数:

key - to search for

storage - to search within (an array of type T)

size - number of data items in the storage

initialGuess - for key position

返回:

index of the key , if found, - index of the insertion point, if not

getMemory

public int getMemory(Value obj)

从接口复制的说明: DataType

Calculates the amount of used memory in bytes.

指定者:

getMemory 在接口中 DataType<Value>

参数:

obj - the object

返回:

the used memory

isMemoryEstimationAllowed

public boolean isMemoryEstimationAllowed()

从接口复制的说明: DataType

Whether memory estimation based on previously seen values is allowed/desirable

指定者:

isMemoryEstimationAllowed 在接口中 DataType<Value>

返回:

true if memory estimation is allowed

write

public void write(WriteBuffer buff,
                  Value obj)

从接口复制的说明: DataType

Write an object.

指定者:

write 在接口中 DataType<Value>

参数:

buff - the target buffer

obj - the value

write

public void write(WriteBuffer buff,
                  Object storage,
                  int len)

从接口复制的说明: DataType

Write a list of objects.

指定者:

write 在接口中 DataType<Value>

参数:

buff - the target buffer

storage - the objects

len - the number of objects to write

read

public Value read(ByteBuffer buff)

从接口复制的说明: DataType

Read an object.

指定者:

read 在接口中 DataType<Value>

参数:

buff - the source buffer

返回:

the object

read

public void read(ByteBuffer buff,
                 Object storage,
                 int len)

从接口复制的说明: DataType

Read a list of objects.

指定者:

read 在接口中 DataType<Value>

参数:

buff - the target buffer

storage - the objects

len - the number of objects to read

createStorage

public Value[] createStorage(int size)

从接口复制的说明: DataType

Create storage object of array type to hold values

指定者:

createStorage 在接口中 DataType<Value>

参数:

size - number of values to hold

返回:

storage object