io.permazen.core

Class Layout

java.lang.Object

io.permazen.core.Layout

public final class Layout
extends Object

Constants and utility methods relating to the encoding and layout of a Database in a key/value store.

The key/value space is divided into a data area and a meta-data area. The data area contains object data as well as simple and composite index data. The meta-data area contains a recognizable signature, encoding format version, each recorded schema version, the object version index data, and a range reserved for user applications.

See Also:

LAYOUT.txt

Field Summary

Fields

Modifier and Type	Field and Description
static int	CURRENT_FORMAT_VERSION The current Database layout format version (2).
static int	FORMAT_VERSION_1 The original Database layout format version #1.
static int	FORMAT_VERSION_2 Database layout format version #2.

Method Summary

Modifier and Type	Method and Description
static byte[]	buildSchemaKey(int version) Get the key corresponding to the specified schema version.
static byte[]	buildVersionIndexKey(ObjId id, int version) Build the key for an object version index entry.
static void	copyMetaData(KVStore src, KVStore dst) Copy non-object meta-data from one KVStore to another.
static SchemaModel	decodeSchema(byte[] value, int formatVersion) Decode schema XML from a schema version meta-data entry.
static void	deleteObjectData(KVStore kv) Delete all object and index data from the given KVStore.
static byte[]	encodeSchema(SchemaModel schemaModel, int formatVersion) Encode schema XML for a schema version meta-data entry.
static byte[]	getFormatVersionKey() Get the key under which the database format version is encoded.
static byte[]	getMetaDataKeyPrefix() Get the common prefix of all meta-data keys.
static KeyRange	getMetaDataKeyRange() Get the meta-data key range.
static byte[]	getObjectVersionIndexKeyPrefix() Get the common prefix of all object version index entries.
static byte[]	getSchemaKey(int version) Get the key in the meta-data area corresponding to the schema with the given version number.
static byte[]	getSchemaKeyPrefix() Get the common prefix of all schema version keys.
static KeyRange	getSchemaKeyRange() Get the schema key range.
static byte[]	getUserMetaDataKeyPrefix() Get the common prefix of all user-defined meta-data keys.
static CoreIndex<Integer,ObjId>	getVersionIndex(KVStore kv) Get a CoreIndex view of the object version index in a key/value database.

Methods inherited from class java.lang.Object

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

Field Detail

FORMAT_VERSION_1

public static final int FORMAT_VERSION_1

The original Database layout format version #1.

See Also:

Constant Field Values

FORMAT_VERSION_2

public static final int FORMAT_VERSION_2

Database layout format version #2.

This version switched to compressed schema XML.

See Also:

Constant Field Values

CURRENT_FORMAT_VERSION

public static final int CURRENT_FORMAT_VERSION

The current Database layout format version (2).

See Also:

Constant Field Values

Method Detail

getMetaDataKeyPrefix

public static byte[] getMetaDataKeyPrefix()

Get the common prefix of all meta-data keys.

Returns:

meta-data prefix bytes

getMetaDataKeyRange

public static KeyRange getMetaDataKeyRange()

Get the meta-data key range.

Returns:

meta-data key range

getFormatVersionKey

public static byte[] getFormatVersionKey()

Get the key under which the database format version is encoded.

The existence of this key also serves to identify a Permazen database.

Returns:

meta-data prefix bytes

getSchemaKeyPrefix

public static byte[] getSchemaKeyPrefix()

Get the common prefix of all schema version keys.

Returns:

schema version key prefix

getSchemaKeyRange

public static KeyRange getSchemaKeyRange()

Get the schema key range.

Returns:

schema key range

buildSchemaKey

public static byte[] buildSchemaKey(int version)

Get the key corresponding to the specified schema version.

Parameters:

version - schema version

Returns:

schema key

Throws:

IllegalArgumentException - if version is zero or negative

getObjectVersionIndexKeyPrefix

public static byte[] getObjectVersionIndexKeyPrefix()

Get the common prefix of all object version index entries.

Returns:

object version index key prefix

getUserMetaDataKeyPrefix

public static byte[] getUserMetaDataKeyPrefix()

Get the common prefix of all user-defined meta-data keys.

Returns:

user meta-data key prefix

getVersionIndex

public static CoreIndex<Integer,ObjId> getVersionIndex(KVStore kv)

Get a CoreIndex view of the object version index in a key/value database.

Parameters:

kv - key/value data

Returns:

object version index

Throws:

IllegalArgumentException - if kv is null

buildVersionIndexKey

public static byte[] buildVersionIndexKey(ObjId id,
                                          int version)

Build the key for an object version index entry.

Parameters:

id - object ID

version - object version

Returns:

version index entry key

Throws:

IllegalArgumentException - if id is null

IllegalArgumentException - if version is non-positive

decodeSchema

public static SchemaModel decodeSchema(byte[] value,
                                       int formatVersion)

Decode schema XML from a schema version meta-data entry.

Parameters:

value - encoded schema from key/value pair

formatVersion - database format version

Returns:

decoded schema

Throws:

InvalidSchemaException - if schema is invalid

IllegalArgumentException - if formatVersion is invalid

IllegalArgumentException - if value is null

encodeSchema

public static byte[] encodeSchema(SchemaModel schemaModel,
                                  int formatVersion)

Encode schema XML for a schema version meta-data entry.

Parameters:

schemaModel - schema

formatVersion - database format version

Returns:

encoded schema for key/value pair

Throws:

IllegalArgumentException - if formatVersion is invalid

IllegalArgumentException - if schemaModel is null

getSchemaKey

public static byte[] getSchemaKey(int version)

Get the key in the meta-data area corresponding to the schema with the given version number.

Parameters:

version - schema version number

Returns:

key for schema version

Throws:

IllegalArgumentException - if version is non-positive

deleteObjectData

public static void deleteObjectData(KVStore kv)

Delete all object and index data from the given KVStore.

Upon return, the KVStore will still contain meta-data, but not any objects.

Parameters:

kv - key/value database

copyMetaData

public static void copyMetaData(KVStore src,
                                KVStore dst)

Copy non-object meta-data from one KVStore to another.

This copies all meta-data except the object version index. Any existing key/value pairs in the destination meta-data range are not removed prior to the copy.

Parameters:

src - source key/value database

dst - destination key/value database