Package org.basex.data

Class DiskData

java.lang.Object

org.basex.data.Data

org.basex.data.DiskData

public final class DiskData
extends Data

This class stores and organizes the database table and the index structures for textual content in a compressed disk structure. The table mapping is documented in Data. Texts may be inlined on disk. The bits of the first byte of the 5-byte text reference can be decoded as follows:

 Bit 0 [INLINED]    indicates if value is inlined in table or stored externally
 Bit 1 [COMPRESSED] indicates if value is compressed
 Bit 2 [STRING]     indicates if an inlined value is a string

 - INLINED (text is inlined):
   - STRING (value is string):
     - Bits 4-7 contain string length
     - 32 remaining bits contain inlined string
     - COMPRESSED: unpack and return inlined text
     - NOT COMPRESSED: return text unchanged
   - NOT STRING (value is integer):
     - return 32 bits of remaining 4 bytes as integer
 - NOT INLINED (text is stored externally):
   - 38 remaining bits contain text reference
   - COMPRESSED: unpack and return external text
   - NOT COMPRESSED: return external text unchanged
 

Author:

BaseX Team 2005-21, BSD License, Christian Gruen, Tim Petrowsky

Field Summary

Fields inherited from class org.basex.data.Data

ATTR, attrIndex, attrNames, closed, COMM, dbid, DOC, ELEM, elemNames, ftIndex, idmap, meta, nspaces, paths, PI, resources, table, TEXT, textIndex, tokenIndex, updateDists

Constructor Summary

Constructors

Constructor	Description
DiskData(MetaData meta)	Default constructor, called from Open.open(java.lang.String, org.basex.core.Context, org.basex.core.MainOptions).
DiskData(MetaData meta, Names elemNames, Names attrNames, PathIndex paths, Namespaces nspaces)	Internal database constructor, called from DiskBuilder.build().

Method Summary

Modifier and Type	Method	Description
void	close()	Closes the database.
void	createIndex(IndexType type, Command cmd)	Drops the specified index.
protected void	delete(int pre, boolean text)	Deletes the specified text entry.
void	dropIndex(IndexType type)	Drops the specified index.
void	finishUpdate(MainOptions opts)	Finishes an update operation: removes the update file and the exclusive lock.
void	flush(boolean all)	Flushes updated data.
boolean	inMemory()	Indicates if this data instance is in main memory or on disk.
void	startUpdate(MainOptions opts)	Starts an update operation: writes a file to disk to indicate that an update is going on, and exclusively locks the table file.
byte[]	text(int pre, boolean text)	Returns a text (text, comment, pi, document) or attribute value.
double	textDbl(int pre, boolean text)	Returns a text (text, comment, pi, document) or attribute value as double value.
long	textItr(int pre, boolean text)	Returns a text (text, comment, pi, document) or attribute value as integer value.
int	textLen(int pre, boolean text)	Returns the byte length of a (possibly compressed) text (text, comment, pi, document).
protected long	textRef(byte[] value, boolean text)	Generates a reference for a text (text, comment, pi, pi, document) or attribute value.
protected void	updateText(int pre, byte[] value, int kind)	Updates the specified text or attribute value.

Methods inherited from class org.basex.data.Data

atom, attr, attSize, attValue, closed, costs, defaultNs, delete, dist, dist, doc, elem, id, id, index, indexAdd, indexDelete, info, insert, insert, insertAttr, iter, kind, name, nameId, namespaces, nsFlag, nsFlag, parent, pre, qname, replace, size, size, text, textRef, textRef, toString, update, update, uriId

Methods inherited from class java.lang.Object

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

Constructor Details

DiskData

public DiskData(MetaData meta)
         throws IOException

Default constructor, called from Open.open(java.lang.String, org.basex.core.Context, org.basex.core.MainOptions).

Parameters:

meta - meta data

Throws:

IOException - I/O Exception

DiskData

public DiskData(MetaData meta,
 Names elemNames,
 Names attrNames,
 PathIndex paths,
 Namespaces nspaces)
         throws IOException

Internal database constructor, called from DiskBuilder.build().

Parameters:

meta - meta data

elemNames - element names

attrNames - attribute names

paths - path index

nspaces - namespaces

Throws:

IOException - I/O Exception

Method Details

close

public void close()

Description copied from class: Data

Closes the database.

Overrides:

close in class Data

createIndex

public void createIndex(IndexType type,
 Command cmd)
                 throws IOException

Description copied from class: Data

Drops the specified index.

Specified by:

createIndex in class Data

Parameters:

type - index to be dropped

cmd - calling command

Throws:

IOException - I/O exception

dropIndex

public void dropIndex(IndexType type)
               throws BaseXException

Description copied from class: Data

Drops the specified index.

Specified by:

dropIndex in class Data

Parameters:

type - index to be dropped

Throws:

BaseXException - database exception

startUpdate

public void startUpdate(MainOptions opts)
                 throws BaseXException

Description copied from class: Data

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

Specified by:

startUpdate in class Data

Parameters:

opts - main options

Throws:

BaseXException - database exception

finishUpdate

public void finishUpdate(MainOptions opts)

Description copied from class: Data

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

Specified by:

finishUpdate in class Data

Parameters:

opts - main options

flush

public void flush(boolean all)

Description copied from class: Data

Flushes updated data.

Specified by:

flush in class Data

Parameters:

all - flush all data

text

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

Description copied from class: Data

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

Specified by:

text in class Data

Parameters:

pre - pre value

text - text/attribute flag

Returns:

atomized value

textItr

public long textItr(int pre,
 boolean text)

Description copied from class: Data

Returns a text (text, comment, pi, document) or attribute value as integer value. Long.MIN_VALUE is returned if the input is no valid integer.

Specified by:

textItr in class Data

Parameters:

pre - pre value

text - text/attribute flag

Returns:

numeric value

textDbl

public double textDbl(int pre,
 boolean text)

Description copied from class: Data

Returns a text (text, comment, pi, document) or attribute value as double value. Double.NaN is returned if the input is no valid double.

Specified by:

textDbl in class Data

Parameters:

pre - pre value

text - text/attribute flag

Returns:

numeric value

textLen

public int textLen(int pre,
 boolean text)

Description copied from class: Data

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

Specified by:

textLen in class Data

Parameters:

pre - pre value

text - text/attribute flag

Returns:

length

inMemory

public boolean inMemory()

Description copied from class: Data

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

Specified by:

inMemory in class Data

Returns:

result of check

delete

protected void delete(int pre,
 boolean text)

Description copied from class: Data

Deletes the specified text entry.

Specified by:

delete in class Data

Parameters:

pre - pre value

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

updateText

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

Description copied from class: Data

Updates the specified text or attribute value.

Specified by:

updateText in class Data

Parameters:

pre - pre value

value - content

kind - node kind

textRef

protected long textRef(byte[] value,
 boolean text)

Description copied from class: Data

Generates a reference for a text (text, comment, pi, pi, document) or attribute value.

Specified by:

textRef in class Data

Parameters:

value - text to be indexed

text - text/attribute flag

Returns:

reference