com.persistit

Class JournalRecord

java.lang.Object

com.persistit.JournalRecord

public class JournalRecord
extends Object

This class encapsulates the formats of Persistit journal records. There is one inner class per record type. The following describes the byte layout implemented by these classes. All multi-byte integers are stored in big-endian form. General record format:

+0	length
+4	type
+8	timestamp
+16	payload

Type: two ASCII bytes:

JH	Journal Header: written as the first record of each journal file. Identifies the version, creation timestamp of the journal, created timestamp of the journal file and path to which journal file was originally written. +16 Version (long) +24 Journal file size (long) +32 Current journal address (long) +40 Base journal address (long) +48 Journal created timestamp (long) +56 Journal file created timestamp (long) +64 Last valid checkpoint timestamp (long) +72 Reserved (8 bytes) +80 Journal File Path (variable - length determined by record length)
JE	Journal End: written as the last record of each journal file. Indicates that the next valid record is in the next journal file, and confirms that the journal file is complete. Lack of a JE record at the end of a journal file indicates the system did not shut down normally. +16 Current journal address (long) +24 Base journal address (long) +32 Journal created timestamp (long)
IV	Identify Volume: associates an integer handle to a Volume. This handle is referenced by subsequent log records to identify this Volume. The handle has no meaning beyond the scope of one log file; every new log generation gets new IV records. +16 Volume handle (int) +20 Volume Id (long) +28 Volume Path (variable - length determined by record length)
IT	Identify Tree: associates an integer handle to a Tree. This handle is referenced by subsequent log records to identify this Tree. The handle has no meaning beyond the scope of one log file; every new log generation gets new IT records. +16 Tree handle (int) +20 Volume handle (int) +24 Tree Name (variable - length determined by record length)
PA	Page Image +16 Volume handle (int) - refers to a volume defined in a preceding IV record +20 page address (long) +28 leftSize (int) +32 bytes: the first leftSize bytes will go into the page at offset 0 the remaining bytes will go to the end of the page; the middle of the page will be cleared
PM	Page Map: written once near the top of each journal file. Represents the state of the page map at the time the journal rolled over. +16 Instances of the following fixed-length structure (28 bytes), number determined by overall record size +0 Transaction timestamp (long) +8 Journal address (long) +16 Volume handle (int) - refers to a volume defined in a preceding IV record +20 Page address (long)
TM	Transaction Map: written once near the top of each journal file. Represents map of transactions still open (started, but neither rolled back nor committed) at the time the journal rolled over. +16 Instances of the following fixed-length structure (24 bytes) number determined by overall record size +0 Transaction timestamp (long) +8 Journal address (long) +16 isCommitted (byte) - indicates whether this transaction committed
CP	Checkpoint. Specifies a timestamp and a system time in millis at which all pages modified prior to that timestamp are present in the log. +16 System time in milliseconds (long) +24 Base journal address (long)
TX	Transaction update record - encapsulates a set of updates applied to the database. This record type encapsulates SR, DR, DT, DV, and CU records defined below. +16 Commit timestamp, or -1 if the transaction has not committed. +24 Previous record journal address (long). +32 serialized updates as a series of contiguous SR, DR, DT, DV, and CU records

The following sub-record types are encapsulated inside of a TX record. Their format differs from the main record types by not including timestamp or backpointer fields.

SR	Store Record - specifies a Tree into which a key/value pair should be inserted +8 Tree handle (int) - matches a tree identified in a preceding IT record +12 Key size (short) +14 Key bytes immediately followed by Value bytes (variable).
DR	Delete Record - specifies a Tree and two Keys: all key/value pairs between these two keys (inclusive) are deleted. The Key bytes field defines two keys, key1 and key2. These delimit the range to be deleted. The first Key1_size bytes of this field contain the encoded key1 value. The remaining bytes define key2. The first Elision_count bytes of Key2 are the same as Key1; only the remaining unique bytes are stored in the record. +8 Tree handle (int) - matches a tree identified in a preceding IT record +12 Key1_size (short) +14 Key2 Elision_count (short) +16 Key bytes
DT	Delete Tree - specifies a Tree to be deleted. +8 Tree handle (int) - matches a tree identified in a preceding IT record
DV	Delete Volume - specifies a Volume to be deleted. +8 Volume handle (int) - matches a volume identified in a preceding IV record
D1	Delta with 1 long-valued argument - encapsulates an update with argument to a Delta (see @link Accumulator} instance +8 Tree handle (int) - matches a tree identified in a preceding IT record +12 index (char) - an Accumulator index +14 type (char) - type of Accumulator (0=SUM, 1=MAX, 2=MIN, 3=SEQ) +16 argument (long) - value by which the Delta is to be adjusted
D0	Delta with no argument - encapsulates an update with a argument value of 1 to a Delta (see @link Accumulator} instance +8 Tree handle (int) - matches a tree identified in a preceding IT record +12 index (char) - an Accumulator index +14 type (char) - type of Accumulator (0=SUM, 1=MAX, 2=MIN, 3=SEQ)

Field Summary

Fields

Modifier and Type	Field and Description
static int[]	TYPES

Constructor Summary

Constructors

Constructor and Description
JournalRecord()

Method Summary

Modifier and Type	Method and Description
static long	getTimestamp(ByteBuffer bb)
static int	getType(ByteBuffer bb)
static boolean	isValidType(int t)
static void	putTimestamp(ByteBuffer bb, long timestamp)
static String	str(int t)

Methods inherited from class java.lang.Object

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

Field Detail

TYPES

public static final int[] TYPES

Constructor Detail

JournalRecord

public JournalRecord()

Method Detail

isValidType

public static boolean isValidType(int t)

str

public static String str(int t)

getType

public static int getType(ByteBuffer bb)

getTimestamp

public static long getTimestamp(ByteBuffer bb)

putTimestamp

public static void putTimestamp(ByteBuffer bb,
                                long timestamp)