org.h2.value

Class ValueLob

java.lang.Object

org.h2.value.Value

org.h2.value.ValueLob

public class ValueLob
extends Value

Implementation of the BLOB and CLOB data types. Small objects are kept in memory and stored in the record. Large objects are stored in their own files. When large objects are set in a prepared statement, they are first stored as 'temporary' files. Later, when they are used in a record, and when the record is stored, the lob files are linked: the file is renamed using the file format (tableId).(objectId). There is one exception: large variables are stored in the file (-1).(objectId). When lobs are deleted, they are first renamed to a temp file, and if the delete operation is committed the file is deleted. Data compression is supported.

Nested Class Summary

Nested classes/interfaces inherited from class org.h2.value.Value

Value.ValueBlob, Value.ValueClob

Field Summary

Fields inherited from class org.h2.value.Value

ARRAY, BLOB, BOOLEAN, BYTE, BYTES, CLOB, DATE, DECIMAL, DOUBLE, ENUM, FLOAT, GEOMETRY, INT, JAVA_OBJECT, LONG, NULL, RESULT_SET, SHORT, STRING, STRING_FIXED, STRING_IGNORECASE, TIME, TIMESTAMP, TIMESTAMP_TZ, TYPE_COUNT, UNKNOWN, UUID

Method Summary

Modifier and Type	Method and Description
protected int	compareSecure(Value v, CompareMode mode) Compare the value with another value of the same type.
Value	convertPrecision(long precision, boolean force) Convert the precision to the requested value.
Value	convertTo(int t, int precision, Mode mode, java.lang.Object column, java.lang.String[] enumerators) Convert a lob to another data type.
void	convertToFileIfRequired(DataHandler h) Store the lob data to a file if the size of the buffer is larger than the maximum size for an in-place lob.
Value	copy(DataHandler h, int tabId) Copy a large value, to be used in the given table.
ValueLob	copyToTemp() Create an independent copy of this temporary value.
boolean	equals(java.lang.Object other) Check if the two values have the same hash code.
byte[]	getBytes()
byte[]	getBytesNoCopy()
int	getDisplaySize() Get the display size in characters.
java.lang.String	getFileName() Get the current file name where the lob is saved.
java.io.InputStream	getInputStream()
java.io.InputStream	getInputStream(long oneBasedOffset, long length) Get the input stream
int	getMemory() Get the memory used by this object.
java.lang.Object	getObject() Get the value as an object.
int	getObjectId() Get the current object id of this lob.
long	getPrecision() Get the precision.
java.io.Reader	getReader()
java.io.Reader	getReader(long oneBasedOffset, long length) Get the reader
byte[]	getSmall() Get the data if this a small lob value.
java.lang.String	getSQL() Get the SQL expression for this value.
java.lang.String	getString() Get the value as a string.
int	getTableId() Get the current table id of this lob.
java.lang.String	getTraceSQL() Get a medium size SQL expression for debugging or tracing.
int	getType() Get the value type.
int	hashCode()
boolean	isCompressed() Check if this lob value is compressed.
boolean	isLinkedToTable() Check if this value is linked to a specific table.
static ValueLob	openLinked(int type, DataHandler handler, int tableId, int objectId, long precision, boolean compression) Create a LOB value with the given parameters.
static ValueLob	openUnlinked(int type, DataHandler handler, int tableId, int objectId, long precision, boolean compression, java.lang.String fileName) Create a LOB value with the given parameters.
void	remove() Remove the underlying resource, if any.
void	set(java.sql.PreparedStatement prep, int parameterIndex) Set the value as a parameter in a prepared statement.

Methods inherited from class org.h2.value.Value

add, checkPrecision, clearCache, compareTo, compareTypeSafe, convertScale, convertTo, convertTo, convertToEnum, copyToResult, divide, getBigDecimal, getBoolean, getByte, getDataHandler, getDate, getDouble, getFloat, getHigherOrder, getInt, getLong, getResultSet, getScale, getShort, getSignum, getTime, getTimestamp, modulus, multiply, negate, subtract, throwUnsupportedExceptionForType, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

openLinked

public static ValueLob openLinked(int type,
                                  DataHandler handler,
                                  int tableId,
                                  int objectId,
                                  long precision,
                                  boolean compression)

Create a LOB value with the given parameters.

Parameters:

type - the data type

handler - the file handler

tableId - the table object id

objectId - the object id

precision - the precision (length in elements)

compression - if compression is used

Returns:

the value object

openUnlinked

public static ValueLob openUnlinked(int type,
                                    DataHandler handler,
                                    int tableId,
                                    int objectId,
                                    long precision,
                                    boolean compression,
                                    java.lang.String fileName)

Create a LOB value with the given parameters.

Parameters:

type - the data type

handler - the file handler

tableId - the table object id

objectId - the object id

precision - the precision (length in elements)

compression - if compression is used

fileName - the file name

Returns:

the value object

convertTo

public Value convertTo(int t,
                       int precision,
                       Mode mode,
                       java.lang.Object column,
                       java.lang.String[] enumerators)

Convert a lob to another data type. The data is fully read in memory except when converting to BLOB or CLOB.

Overrides:

convertTo in class Value

Parameters:

t - the new type

precision - the precision of the column to convert this value to. The special constant -1 is used to indicate that the precision plays no role when converting the value

mode - the database mode

column - the column (if any), used for to improve the error message if conversion fails

enumerators - the ENUM datatype enumerators (if any), for dealing with ENUM conversions

Returns:

the converted value

isLinkedToTable

public boolean isLinkedToTable()

Description copied from class: Value

Check if this value is linked to a specific table. For values that are kept fully in memory, this method returns false.

Overrides:

isLinkedToTable in class Value

Returns:

true if it is

getFileName

public java.lang.String getFileName()

Get the current file name where the lob is saved.

Returns:

the file name or null

remove

public void remove()

Description copied from class: Value

Remove the underlying resource, if any. For values that are kept fully in memory this method has no effect.

Overrides:

remove in class Value

copy

public Value copy(DataHandler h,
                  int tabId)

Description copied from class: Value

Copy a large value, to be used in the given table. For values that are kept fully in memory this method has no effect.

Overrides:

copy in class Value

Parameters:

h - the data handler

tabId - the table where this object is used

Returns:

the new value or itself

getTableId

public int getTableId()

Get the current table id of this lob.

Overrides:

getTableId in class Value

Returns:

the table id

getObjectId

public int getObjectId()

Get the current object id of this lob.

Returns:

the object id

getType

public int getType()

Description copied from class: Value

Get the value type.

Specified by:

getType in class Value

Returns:

the type

getPrecision

public long getPrecision()

Description copied from class: Value

Get the precision.

Specified by:

getPrecision in class Value

Returns:

the precision

getString

public java.lang.String getString()

Description copied from class: Value

Get the value as a string.

Specified by:

getString in class Value

Returns:

the string

getBytes

public byte[] getBytes()

Overrides:

getBytes in class Value

getBytesNoCopy

public byte[] getBytesNoCopy()

Overrides:

getBytesNoCopy in class Value

hashCode

public int hashCode()

Specified by:

hashCode in class Value

compareSecure

protected int compareSecure(Value v,
                            CompareMode mode)

Description copied from class: Value

Compare the value with another value of the same type.

Specified by:

compareSecure in class Value

Parameters:

v - the other value

mode - the compare mode

Returns:

0 if both values are equal, -1 if the other value is smaller, and 1 otherwise

getObject

public java.lang.Object getObject()

Description copied from class: Value

Get the value as an object.

Specified by:

getObject in class Value

Returns:

the object

getReader

public java.io.Reader getReader()

Overrides:

getReader in class Value

getReader

public java.io.Reader getReader(long oneBasedOffset,
                                long length)

Description copied from class: Value

Get the reader

Overrides:

getReader in class Value

Parameters:

oneBasedOffset - the offset (1 means no offset)

length - the requested length

Returns:

the new reader

getInputStream

public java.io.InputStream getInputStream()

Overrides:

getInputStream in class Value

getInputStream

public java.io.InputStream getInputStream(long oneBasedOffset,
                                          long length)

Description copied from class: Value

Get the input stream

Overrides:

getInputStream in class Value

Parameters:

oneBasedOffset - the offset (1 means no offset)

length - the requested length

Returns:

the new input stream

set

public void set(java.sql.PreparedStatement prep,
                int parameterIndex)
         throws java.sql.SQLException

Description copied from class: Value

Set the value as a parameter in a prepared statement.

Specified by:

set in class Value

Parameters:

prep - the prepared statement

parameterIndex - the parameter index

Throws:

java.sql.SQLException

getSQL

public java.lang.String getSQL()

Description copied from class: Value

Get the SQL expression for this value.

Specified by:

getSQL in class Value

Returns:

the SQL expression

getTraceSQL

public java.lang.String getTraceSQL()

Description copied from class: Value

Get a medium size SQL expression for debugging or tracing. If the precision is too large, only a subset of the value is returned.

Overrides:

getTraceSQL in class Value

Returns:

the SQL expression

getSmall

public byte[] getSmall()

Get the data if this a small lob value.

Overrides:

getSmall in class Value

Returns:

the data

getDisplaySize

public int getDisplaySize()

Description copied from class: Value

Get the display size in characters.

Specified by:

getDisplaySize in class Value

Returns:

the display size

equals

public boolean equals(java.lang.Object other)

Description copied from class: Value

Check if the two values have the same hash code. No data conversion is made; this method returns false if the other object is not of the same class. For some values, compareTo may return 0 even if equals return false. Example: ValueDecimal 0.0 and 0.00.

Specified by:

equals in class Value

Parameters:

other - the other value

Returns:

true if they are equal

convertToFileIfRequired

public void convertToFileIfRequired(DataHandler h)

Store the lob data to a file if the size of the buffer is larger than the maximum size for an in-place lob.

Parameters:

h - the data handler

isCompressed

public boolean isCompressed()

Check if this lob value is compressed.

Returns:

true if it is

getMemory

public int getMemory()

Description copied from class: Value

Get the memory used by this object.

Overrides:

getMemory in class Value

Returns:

the memory used in bytes

copyToTemp

public ValueLob copyToTemp()

Create an independent copy of this temporary value. The file will not be deleted automatically.

Overrides:

copyToTemp in class Value

Returns:

the value

convertPrecision

public Value convertPrecision(long precision,
                              boolean force)

Description copied from class: Value

Convert the precision to the requested value. The precision of the returned value may be somewhat larger than requested, because values with a fixed precision are not truncated.

Overrides:

convertPrecision in class Value

Parameters:

precision - the new precision

force - true if losing numeric precision is allowed

Returns:

the new value