org.neo4j.index.internal.gbptree

Interface Layout<KEY,VALUE>

Type Parameters:

KEY - type of key

VALUE - type of value

All Superinterfaces:

Comparator<KEY>

All Known Implementing Classes:

Layout.Adapter

public interface Layout<KEY,VALUE>
extends Comparator<KEY>

Main point of interaction for customizing a GBPTree, how its keys and values are represented as bytes and what keys and values contains.

Additionally custom meta data can be supplied, which will be persisted in GBPTree.

Rather extend Layout.Adapter as to get standard implementation of e.g. Layout.Adapter.toString().

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	Layout.Adapter<KEY,VALUE> Adapter for Layout, which contains convenient standard implementations of some methods.

Method Summary

Modifier and Type	Method and Description
KEY	copyKey(KEY key, KEY into) Copies contents of key to into.
long	identifier() Used as a checksum for when loading an index after creation, to verify that the same layout is used, as the one it was initially created with.
int	keySize()
int	majorVersion()
int	minorVersion()
static long	namedIdentifier(String name, int checksum) Utility method for generating an identifier().
KEY	newKey()
VALUE	newValue()
void	readKey(org.neo4j.io.pagecache.PageCursor cursor, KEY into) Reads key contents at cursor at its current offset into key.
default void	readMetaData(org.neo4j.io.pagecache.PageCursor cursor) Reads meta data specific to this layout instance from cursor at its current offset.
void	readValue(org.neo4j.io.pagecache.PageCursor cursor, VALUE into) Reads value contents at cursor at its current offset into value.
int	valueSize()
void	writeKey(org.neo4j.io.pagecache.PageCursor cursor, KEY key) Writes contents of key into cursor at its current offset.
default void	writeMetaData(org.neo4j.io.pagecache.PageCursor cursor) Writes meta data specific to this layout instance to cursor at its current offset.
void	writeValue(org.neo4j.io.pagecache.PageCursor cursor, VALUE value) Writes contents of value into cursor at its current offset.

Methods inherited from interface java.util.Comparator

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

Method Detail

newKey

KEY newKey()

Returns:

new key instance.

copyKey

KEY copyKey(KEY key,
            KEY into)

Copies contents of key to into.

Parameters:

key - key (left unchanged as part of this call) to copy contents from.

into - key (changed as part of this call) to copy contents into.

Returns:

the provided into instance for convenience.

newValue

VALUE newValue()

Returns:

new value instance.

keySize

int keySize()

Returns:

size, in bytes, of a key.

valueSize

int valueSize()

Returns:

size, in bytes, of a value.

writeKey

void writeKey(org.neo4j.io.pagecache.PageCursor cursor,
              KEY key)

Writes contents of key into cursor at its current offset.

Parameters:

cursor - PageCursor to write into, at current offset.

key - key containing data to write.

writeValue

void writeValue(org.neo4j.io.pagecache.PageCursor cursor,
                VALUE value)

Writes contents of value into cursor at its current offset.

Parameters:

cursor - PageCursor to write into, at current offset.

value - value containing data to write.

readKey

void readKey(org.neo4j.io.pagecache.PageCursor cursor,
             KEY into)

Reads key contents at cursor at its current offset into key.

Parameters:

cursor - PageCursor to read from, at current offset.

into - key instances to read into.

readValue

void readValue(org.neo4j.io.pagecache.PageCursor cursor,
               VALUE into)

Reads value contents at cursor at its current offset into value.

Parameters:

cursor - PageCursor to read from, at current offset.

into - value instances to read into.

identifier

long identifier()

Used as a checksum for when loading an index after creation, to verify that the same layout is used, as the one it was initially created with.

Returns:

a long acting as an identifier, written in the header of an index.

majorVersion

int majorVersion()

Returns:

major version of layout. Will be compared to version written into meta page when opening index.

minorVersion

int minorVersion()

Returns:

minor version of layout. Will be compared to version written into meta page when opening index.

writeMetaData

default void writeMetaData(org.neo4j.io.pagecache.PageCursor cursor)

Writes meta data specific to this layout instance to cursor at its current offset.

Parameters:

cursor - PageCursor to write into, at its current offset.

readMetaData

default void readMetaData(org.neo4j.io.pagecache.PageCursor cursor)

Reads meta data specific to this layout instance from cursor at its current offset. The read meta data must also be verified against meta data provided in constructor of this Layout. Constructor-provided meta data can be null to skip this verification. if read meta data doesn't match with the meta data provided in constructor PageCursor.setCursorException(String) should be called with appropriate error message.

Parameters:

cursor - PageCursor to read from, at its current offset.

namedIdentifier

static long namedIdentifier(String name,
                            int checksum)

Utility method for generating an identifier().

Parameters:

name - name to be part of this identifier, must at most be 4 characters.

checksum - checksum to include into the identifier.

Returns:

a long which is a combination of name and checksum.