org.basex.data

Class Data

java.lang.Object

org.basex.data.Data

Direct Known Subclasses:

DiskData, MemData

public abstract class Data
extends java.lang.Object

This class represents a database instance. It provides low-level access to all properties and values stored in a single database. An XML node is accessed by its pre value, which is not stored itself, but given by the table position. The following restrictions are imposed on the data:

• The table is limited to 2^31 entries (pre values are signed int's)
• A maximum of 2^15 different tag and attribute names is allowed
• A maximum of 2^8 different namespaces is allowed

Each node occupies 128 bits. The current storage layout looks as follows:

 COMMON ATTRIBUTES:
 - Byte     0:  KIND: Node kind (bits: 2-0)
 - Byte 12-15:  UNID: Unique Node ID
 DOCUMENT NODES (kind = 0):
 - Byte  3- 7:  TEXT: Text reference
 - Byte  8-11:  SIZE: Number of descendants
 ELEMENT NODES (kind = 1):
 - Byte     0:  ATTS: Number of attributes (bits: 7-3).
                      Calculated in real-time, if bit range is too small
 - Byte  1- 2:  NAME: Namespace Flag (bit: 15), Name (bits: 14-0)
 - Byte     3:  NURI: Namespace URI
 - Byte  4- 7:  DIST: Distance to parent node
 - Byte  8-11:  SIZE: Number of descendants
 TEXT, COMMENT, PI NODES (kind = 2, 4, 5):
 - Byte  3- 7:  TEXT: Text reference
 - Byte  8-11:  DIST: Distance to parent node
 ATTRIBUTE NODES (kind = 3):
 - Byte     0:  DIST: Distance to parent node (bits: 7-3)
                      Calculated in real-time, if bit range is too small
 - Byte  1- 2:  NAME: Namespace Flag (bit: 15), Name (bits: 14-0)
 - Byte  3- 7:  TEXT: Attribute value reference
 - Byte    11:  NURI: Namespace (bits: 7-3)
 

As all methods of this class are optimized for performance, no checks are performed on the arguments (e.g.: if the string value of a text node is requested, the specified pre value must point to a text node).

Author:

BaseX Team 2005-12, BSD License, Christian Gruen

Field Summary

Fields

Modifier and Type	Field and Description
Names	atnindex Attribute name index.
static byte	ATTR Node kind: attribute (code: 3).
Index	atvindex Attribute value index.
static byte	COMM Node kind: comment (code: 4).
static byte	DOC Node kind: document (code: 0).
static byte	ELEM Node kind: element (code: 1).
Index	ftxindex Full-text index instance.
MetaData	meta Meta data.
Namespaces	nspaces Namespace index.
PathSummary	paths Path summary index.
static byte	PI Node kind: processing instruction (code: 5).
int	pins Number of current database users.
Resources	resources Resource index.
Names	tagindex Tag index.
static byte	TEXT Node kind: text (code: 2).
Index	txtindex Text index.

Constructor Summary

Constructors

Constructor and Description
Data()

Method Summary

Methods

Modifier and Type	Method and Description
byte[]	atom(int pre) Returns an atomized content for any node kind.
void	attr(int pre, int dist, int name, byte[] value, int uri, boolean ne) Adds an attribute entry to the internal update buffer.
int	attSize(int pre, int kind) Returns a number of attributes.
byte[]	attValue(int att, int pre) Finds the specified attribute and returns its value.
abstract void	close() Closes the database.
abstract void	closeIndex(IndexToken.IndexType type) Closes the specified index.
int	count(IndexToken token) Returns the number of indexed pre references for the specified token.
void	delete(int pre) Deletes a node and its descendants.
protected abstract void	delete(int pre, boolean text) Deletes the specified text entry.
void	doc(int pre, int size, byte[] value) Adds a document entry to the internal update buffer.
void	elem(int dist, int name, int asize, int size, int uri, boolean ne) Adds an element entry to the internal update buffer.
abstract void	finishUpdate() Finishes an update operation: removes the update file and the exclusive lock.
int	id(int pre) Returns a unique node id.
protected abstract long	index(int pre, int id, byte[] value, int kind) Indexes a text and returns the reference.
protected abstract void	indexDelete(int pre, int size) Delete a node and its descendants from the corresponding indexes.
byte[]	info(IndexToken.IndexType type) Returns info on the specified index structure.
boolean	inMemory() Indicates if this data instance is in main memory or on disk.
void	insert(int pre) Inserts the internal buffer to the storage without updating the table structure.
void	insert(int ipre, int ipar, Data data) Inserts a data instance at the specified pre value.
void	insertAttr(int pre, int par, Data data) Inserts attributes.
boolean	isEmpty() Checks if the database contains no documents.
IndexIterator	iter(IndexToken token) Returns the indexed pre references for the specified token.
int	kind(int pre) Returns the node kind, which may be DOC, ELEM, TEXT, ATTR, COMM or PI.
int	name(int pre) Returns a reference to the tag or attribute name id.
byte[]	name(int pre, int kind) Returns a tag, attribute or pi name.
Atts	ns(int pre) Returns all namespace keys and values.
boolean	nsFlag(int pre) Returns the namespace flag of the addressed element.
void	nsFlag(int pre, boolean ne) Sets the namespace flag.
int	parent(int pre, int kind) Returns a pre value of the parent node.
int	pre(int id) Returns a pre value.
int[]	pre(int[] ids, int off, int len) Returns pre values.
void	replace(int rpre, Data data) Replaces parts of the database with the specified data instance.
abstract void	setIndex(IndexToken.IndexType type, Index index) Assigns the specified index.
boolean	single() Checks if the database contains a single document.
int	size(int pre, int kind) Returns a size value (number of descendant table entries).
void	size(int pre, int kind, int value) Sets the size value.
abstract boolean	startUpdate() Starts an update operation: writes a file to disk to indicate that an update is going on, and exclusively locks the table.
abstract byte[]	text(int pre, boolean text) Returns a text (text, comment, pi) or attribute value.
void	text(int pre, int dist, byte[] value, int kind) Adds a text entry to the internal update buffer.
abstract double	textDbl(int pre, boolean text) Returns a text (text, comment, pi) or attribute value as double value.
abstract long	textItr(int pre, boolean text) Returns a text (text, comment, pi) or attribute value as integer value.
abstract int	textLen(int pre, boolean text) Returns the byte length of a text (text, comment, pi).
java.lang.String	toString()
void	update(int pre, int kind, byte[] value) Updates (replaces) the value of a single text, comment, pi or attribute node.
void	update(int pre, int kind, byte[] name, byte[] uri) Updates (renames) an element, attribute or pi name.
protected abstract void	updateText(int pre, byte[] value, int kind) Updates the specified text or attribute value.
int	uri(int pre, int kind) Returns a reference to the namespace of the addressed element or attribute.

Methods inherited from class java.lang.Object

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

Field Detail

DOC

public static final byte DOC

Node kind: document (code: 0).

See Also:

Constant Field Values

ELEM

public static final byte ELEM

Node kind: element (code: 1).

See Also:

Constant Field Values

TEXT

public static final byte TEXT

Node kind: text (code: 2).

See Also:

Constant Field Values

ATTR

public static final byte ATTR

Node kind: attribute (code: 3).

See Also:

Constant Field Values

COMM

public static final byte COMM

Node kind: comment (code: 4).

See Also:

Constant Field Values

PI

public static final byte PI

Node kind: processing instruction (code: 5).

See Also:

Constant Field Values

resources

public final Resources resources

Resource index.

meta

public MetaData meta

Meta data.

tagindex

public Names tagindex

Tag index.

atnindex

public Names atnindex

Attribute name index.

nspaces

public Namespaces nspaces

Namespace index.

paths

public PathSummary paths

Path summary index.

txtindex

public Index txtindex

Text index.

atvindex

public Index atvindex

Attribute value index.

ftxindex

public Index ftxindex

Full-text index instance.

pins

public int pins

Number of current database users.

Constructor Detail

Data

public Data()

Method Detail

close

public abstract void close()

Closes the database.

isEmpty

public final boolean isEmpty()

Checks if the database contains no documents. Empty databases can be recognized by a single document node.

Returns:

result of check

single

public final boolean single()

Checks if the database contains a single document.

Returns:

result of check

closeIndex

public abstract void closeIndex(IndexToken.IndexType type)

Closes the specified index.

Parameters:

type - index to be closed

setIndex

public abstract void setIndex(IndexToken.IndexType type,
            Index index)

Assigns the specified index.

Parameters:

type - index to be opened

index - index instance

startUpdate

public abstract boolean startUpdate()

Starts an update operation: writes a file to disk to indicate that an update is going on, and exclusively locks the table.

Returns:

success flag

finishUpdate

public abstract void finishUpdate()

Finishes an update operation: removes the update file and the exclusive lock.

iter

public final IndexIterator iter(IndexToken token)

Returns the indexed pre references for the specified token.

Parameters:

token - index token reference

Returns:

array of sorted pre values

count

public final int count(IndexToken token)

Returns the number of indexed pre references for the specified token.

Parameters:

token - text to be found

Returns:

number of hits

info

public final byte[] info(IndexToken.IndexType type)

Returns info on the specified index structure.

Parameters:

type - index type

Returns:

info

atom

public final byte[] atom(int pre)

Returns an atomized content for any node kind. The atomized value can be an attribute value or XML content.

Parameters:

pre - pre value

Returns:

atomized value

pre

public final int pre(int id)

Returns a pre value.

Parameters:

id - unique node id

Returns:

pre value or -1 if id was not found

pre

public final int[] pre(int[] ids,
        int off,
        int len)

Returns pre values.

Parameters:

ids - unique node ids

off - start offset

len - number of ids

Returns:

sorted pre values

id

public final int id(int pre)

Returns a unique node id.

Parameters:

pre - pre value

Returns:

node id

kind

public final int kind(int pre)

Returns the node kind, which may be DOC, ELEM, TEXT, ATTR, COMM or PI.

Parameters:

pre - pre value

Returns:

node kind

parent

public final int parent(int pre,
         int kind)

Returns a pre value of the parent node.

Parameters:

pre - pre value

kind - node kind

Returns:

pre value of the parent node

size

public final int size(int pre,
       int kind)

Returns a size value (number of descendant table entries).

Parameters:

pre - pre value

kind - node kind

Returns:

size value

attSize

public final int attSize(int pre,
          int kind)

Returns a number of attributes.

Parameters:

pre - pre value

kind - node kind

Returns:

number of attributes

attValue

public final byte[] attValue(int att,
              int pre)

Finds the specified attribute and returns its value.

Parameters:

att - the attribute id of the attribute to be found

pre - pre value

Returns:

attribute value

name

public final int name(int pre)

Returns a reference to the tag or attribute name id.

Parameters:

pre - pre value

Returns:

token reference

name

public final byte[] name(int pre,
          int kind)

Returns a tag, attribute or pi name.

Parameters:

pre - pre value

kind - node kind

Returns:

name reference

uri

public final int uri(int pre,
      int kind)

Returns a reference to the namespace of the addressed element or attribute.

Parameters:

pre - pre value

kind - node kind

Returns:

namespace URI

nsFlag

public final boolean nsFlag(int pre)

Returns the namespace flag of the addressed element.

Parameters:

pre - pre value

Returns:

namespace flag

ns

public final Atts ns(int pre)

Returns all namespace keys and values. Should be only called for element nodes.

Parameters:

pre - pre value

Returns:

key and value ids

text

public abstract byte[] text(int pre,
          boolean text)

Returns a text (text, comment, pi) or attribute value.

Parameters:

pre - pre value

text - text/attribute flag

Returns:

atomized value

textItr

public abstract long textItr(int pre,
           boolean text)

Returns a text (text, comment, pi) or attribute value as integer value.

Parameters:

pre - pre value

text - text/attribute flag

Returns:

numeric value

textDbl

public abstract double textDbl(int pre,
             boolean text)

Returns a text (text, comment, pi) or attribute value as double value.

Parameters:

pre - pre value

text - text/attribute flag

Returns:

numeric value

textLen

public abstract int textLen(int pre,
          boolean text)

Returns the byte length of a text (text, comment, pi).

Parameters:

pre - pre value

text - text/attribute flag

Returns:

length

update

public final void update(int pre,
          int kind,
          byte[] name,
          byte[] uri)

Updates (renames) an element, attribute or pi name.

Parameters:

pre - pre value

kind - node kind

name - new tag, attribute or pi name

uri - uri

update

public final void update(int pre,
          int kind,
          byte[] value)

Updates (replaces) the value of a single text, comment, pi or attribute node.

Parameters:

pre - pre value to be replaced

kind - node kind

value - value to be updated (tag name, text, comment, pi)

replace

public final void replace(int rpre,
           Data data)

Replaces parts of the database with the specified data instance.

Parameters:

rpre - pre value to be replaced

data - replace data

delete

public final void delete(int pre)

Deletes a node and its descendants.

Parameters:

pre - pre value of the node to delete

insertAttr

public final void insertAttr(int pre,
              int par,
              Data data)

Inserts attributes.

Parameters:

pre - pre value

par - parent of node

data - data instance to copy from

insert

public final void insert(int ipre,
          int ipar,
          Data data)

Inserts a data instance at the specified pre value. Note that the specified data instance must differ from this instance.

Parameters:

ipre - value at which to insert new data

ipar - parent pre value of node

data - data instance to copy from

size

public final void size(int pre,
        int kind,
        int value)

Sets the size value.

Parameters:

pre - pre reference

kind - node kind

value - value to be stored

updateText

protected abstract void updateText(int pre,
              byte[] value,
              int kind)

Updates the specified text or attribute value.

Parameters:

pre - pre value

value - content

kind - node kind

nsFlag

public final void nsFlag(int pre,
          boolean ne)

Sets the namespace flag. Should be only called for element nodes.

Parameters:

pre - pre value

ne - namespace flag

insert

public final void insert(int pre)

Inserts the internal buffer to the storage without updating the table structure.

Parameters:

pre - insert position

delete

protected abstract void delete(int pre,
          boolean text)

Deletes the specified text entry.

Parameters:

pre - pre value

text - text (text, comment or pi) or attribute flag

doc

public final void doc(int pre,
       int size,
       byte[] value)

Adds a document entry to the internal update buffer.

Parameters:

pre - pre value

size - node size

value - document name

elem

public final void elem(int dist,
        int name,
        int asize,
        int size,
        int uri,
        boolean ne)

Adds an element entry to the internal update buffer.

Parameters:

dist - parent distance

name - tag name index

asize - number of attributes

size - node size

uri - namespace uri reference

ne - namespace flag

text

public final void text(int pre,
        int dist,
        byte[] value,
        int kind)

Adds a text entry to the internal update buffer.

Parameters:

pre - pre value

dist - parent distance

value - string value

kind - node kind

attr

public final void attr(int pre,
        int dist,
        int name,
        byte[] value,
        int uri,
        boolean ne)

Adds an attribute entry to the internal update buffer.

Parameters:

pre - pre value

dist - parent distance

name - attribute name

value - attribute value

uri - namespace uri reference

ne - namespace flag

index

protected abstract long index(int pre,
         int id,
         byte[] value,
         int kind)

Indexes a text and returns the reference.

Parameters:

pre - pre value

id - id value

value - text to be indexed

kind - node kind

Returns:

reference

indexDelete

protected abstract void indexDelete(int pre,
               int size)

Delete a node and its descendants from the corresponding indexes.

Parameters:

pre - pre value of the node to delete

size - number of descendants

inMemory

public final boolean inMemory()

Indicates if this data instance is in main memory or on disk.

Returns:

result of check

toString

public final java.lang.String toString()

Overrides:

toString in class java.lang.Object