WALEdit (Apache HBase 1.2.12 API)

java.lang.Object
- org.apache.hadoop.hbase.regionserver.wal.WALEdit

All Implemented Interfaces:

HeapSize, org.apache.hadoop.io.Writable
```
@InterfaceAudience.LimitedPrivate(value={"Replication","Coprocesssor"})
public class WALEdit
extends Object
implements org.apache.hadoop.io.Writable, HeapSize
```
WALEdit: Used in HBase's transaction log (WAL) to represent the collection of edits (KeyValue objects) corresponding to a single transaction. The class implements "Writable" interface for serializing/deserializing a set of KeyValue items. Previously, if a transaction contains 3 edits to c1, c2, c3 for a row R, the WAL would have three log entries as follows: <logseq1-for-edit1>:<eyValue-for-edit-c1> <logseq2-for-edit2>:<KeyValue-for-edit-c2> <logseq3-for-edit3>:<KeyValue-for-edit-c3> This presents problems because row level atomicity of transactions was not guaranteed. If we crash after few of the above appends make it, then recovery will restore a partial transaction. In the new world, all the edits for a given transaction are written out as a single record, for example: <logseq#-for-entire-txn>:<WALEdit-for-entire-txn> where, the WALEdit is serialized as: <-1, # of edits, <KeyValue>, <KeyValue>, ... > For example: <-1, 3, <KV-for-edit-c1>, <KV-for-edit-c2>, <KV-for-edit-c3>> The -1 marker is just a special way of being backward compatible with an old WAL which would have contained a single <KeyValue>. The deserializer for WALEdit backward compatibly detects if the record is an old style KeyValue or the new style WALEdit.

Field Summary

Fields
Modifier and Type	Field and Description
`static byte[]`	`BULK_LOAD`
`private ArrayList<Cell>`	`cells`
`static byte[]`	`COMPACTION`
`private CompressionContext`	`compressionContext`
`static WALEdit`	`EMPTY_WALEDIT`
`static byte[]`	`FLUSH`
`private boolean`	`isReplay`
`private static org.apache.commons.logging.Log`	`LOG`
`static byte[]`	`METAFAMILY`
`static byte[]`	`METAROW`
`static byte[]`	`REGION_EVENT`
`private NavigableMap<byte[],Integer>`	`scopes` Deprecated. Legacy
`private int`	`VERSION_2`

Constructor Summary

Constructors
Constructor and Description

WALEdit()

WALEdit(boolean isReplay)

Constructors
Constructor and Description
`WALEdit()`
`WALEdit(boolean isReplay)`

Method Summary

Methods
Modifier and Type	Method and Description
`WALEdit`	`add(Cell cell)`
`static WALEdit`	`createBulkLoadEvent(HRegionInfo hri, org.apache.hadoop.hbase.protobuf.generated.WALProtos.BulkLoadDescriptor bulkLoadDescriptor)` Create a bulk loader WALEdit
`static WALEdit`	`createCompaction(HRegionInfo hri, org.apache.hadoop.hbase.protobuf.generated.WALProtos.CompactionDescriptor c)` Create a compaction WALEdit
`static WALEdit`	`createFlushWALEdit(HRegionInfo hri, org.apache.hadoop.hbase.protobuf.generated.WALProtos.FlushDescriptor f)`
`static WALEdit`	`createRegionEventWALEdit(HRegionInfo hri, org.apache.hadoop.hbase.protobuf.generated.WALProtos.RegionEventDescriptor regionEventDesc)`
`NavigableMap<byte[],Integer>`	`getAndRemoveScopes()`
`static org.apache.hadoop.hbase.protobuf.generated.WALProtos.BulkLoadDescriptor`	`getBulkLoadDescriptor(Cell cell)` Deserialized and returns a BulkLoadDescriptor from the passed in Cell
`ArrayList<Cell>`	`getCells()`
`static org.apache.hadoop.hbase.protobuf.generated.WALProtos.CompactionDescriptor`	`getCompaction(Cell kv)` Deserialized and returns a CompactionDescriptor is the KeyValue contains one.
`static org.apache.hadoop.hbase.protobuf.generated.WALProtos.FlushDescriptor`	`getFlushDescriptor(Cell cell)`
`static org.apache.hadoop.hbase.protobuf.generated.WALProtos.RegionEventDescriptor`	`getRegionEventDescriptor(Cell cell)`
`static byte[]`	`getRowForRegion(HRegionInfo hri)`
`long`	`heapSize()`
`static boolean`	`isCompactionMarker(Cell cell)` Returns true if the given cell is a serialized `WALProtos.CompactionDescriptor`
`boolean`	`isEmpty()`
`boolean`	`isMetaEdit()`
`static boolean`	`isMetaEditFamily(byte[] f)`
`static boolean`	`isMetaEditFamily(Cell cell)`
`boolean`	`isReplay()`
`void`	`readFields(DataInput in)`
`int`	`readFromCells(Codec.Decoder cellDecoder, int expectedCount)` Reads WALEdit from cells.
`void`	`setCells(ArrayList<Cell> cells)` This is not thread safe.
`void`	`setCompressionContext(CompressionContext compressionContext)`
`int`	`size()`
`String`	`toString()`
`void`	`write(DataOutput out)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

LOG

private static final org.apache.commons.logging.Log LOG

METAFAMILY
```
public static final byte[] METAFAMILY
```

METAROW
```
public static final byte[] METAROW
```

COMPACTION
```
public static final byte[] COMPACTION
```

FLUSH
```
public static final byte[] FLUSH
```

REGION_EVENT

public static final byte[] REGION_EVENT

BULK_LOAD
```
public static final byte[] BULK_LOAD
```

VERSION_2
```
private final int VERSION_2
```
See Also:
Constant Field Values

isReplay
```
private final boolean isReplay
```

cells
```
private ArrayList<Cell> cells
```

EMPTY_WALEDIT

public static final WALEdit EMPTY_WALEDIT

scopes

@Deprecated
private NavigableMap<byte[],Integer> scopes

Deprecated. Legacy

compressionContext

private CompressionContext compressionContext

Constructor Detail

WALEdit
```
public WALEdit()
```

WALEdit
```
public WALEdit(boolean isReplay)
```

Method Detail

isMetaEditFamily
```
public static boolean isMetaEditFamily(byte[] f)
```
Parameters:
f -

Returns:
True is f is METAFAMILY

isMetaEditFamily

public static boolean isMetaEditFamily(Cell cell)

isMetaEdit
```
public boolean isMetaEdit()
```

isReplay
```
public boolean isReplay()
```
Returns:
True when current WALEdit is created by log replay. Replication skips WALEdits from replay.

setCompressionContext

public void setCompressionContext(CompressionContext compressionContext)

add
```
public WALEdit add(Cell cell)
```

isEmpty
```
public boolean isEmpty()
```

size
```
public int size()
```

getCells
```
public ArrayList<Cell> getCells()
```

setCells
```
@InterfaceAudience.Private
public void setCells(ArrayList<Cell> cells)
```
This is not thread safe. This will change the WALEdit and shouldn't be used unless you are sure that nothing else depends on the contents being immutable.

Parameters:
cells - the list of cells that this WALEdit now contains.

getAndRemoveScopes

public NavigableMap<byte[],Integer> getAndRemoveScopes()

readFields
```
public void readFields(DataInput in)
                throws IOException
```
Specified by:

readFields in interface org.apache.hadoop.io.Writable

Throws:

IOException

write
```
public void write(DataOutput out)
           throws IOException
```
Specified by:

write in interface org.apache.hadoop.io.Writable

Throws:

IOException

readFromCells
```
public int readFromCells(Codec.Decoder cellDecoder,
                int expectedCount)
                  throws IOException
```
Reads WALEdit from cells.

Parameters:
cellDecoder - Cell decoder.
expectedCount - Expected cell count.

Returns:
Number of KVs read.

Throws:

IOException

heapSize
```
public long heapSize()
```
Specified by:

heapSize in interface HeapSize

Returns:
Approximate 'exclusive deep size' of implementing object. Includes count of payload and hosting object sizings.

toString
```
public String toString()
```
Overrides:

toString in class Object

createFlushWALEdit

public static WALEdit createFlushWALEdit(HRegionInfo hri,
                         org.apache.hadoop.hbase.protobuf.generated.WALProtos.FlushDescriptor f)

getFlushDescriptor

public static org.apache.hadoop.hbase.protobuf.generated.WALProtos.FlushDescriptor getFlushDescriptor(Cell cell)
                                                                                               throws IOException

Throws:: IOException

createRegionEventWALEdit

public static WALEdit createRegionEventWALEdit(HRegionInfo hri,
                               org.apache.hadoop.hbase.protobuf.generated.WALProtos.RegionEventDescriptor regionEventDesc)

getRegionEventDescriptor

public static org.apache.hadoop.hbase.protobuf.generated.WALProtos.RegionEventDescriptor getRegionEventDescriptor(Cell cell)
                                                                                                           throws IOException

Throws:: IOException

createCompaction

public static WALEdit createCompaction(HRegionInfo hri,
                       org.apache.hadoop.hbase.protobuf.generated.WALProtos.CompactionDescriptor c)

Create a compaction WALEdit

Parameters:: c -
Returns:: A WALEdit that has c serialized as its value

getRowForRegion

public static byte[] getRowForRegion(HRegionInfo hri)

getCompaction

public static org.apache.hadoop.hbase.protobuf.generated.WALProtos.CompactionDescriptor getCompaction(Cell kv)
                                                                                               throws IOException

Deserialized and returns a CompactionDescriptor is the KeyValue contains one.

Parameters:: kv - the key value
Returns:: deserialized CompactionDescriptor or null.
Throws:: IOException

isCompactionMarker
```
public static boolean isCompactionMarker(Cell cell)
```
Returns true if the given cell is a serialized WALProtos.CompactionDescriptor

See Also:
getCompaction(Cell)

createBulkLoadEvent
```
public static WALEdit createBulkLoadEvent(HRegionInfo hri,
                          org.apache.hadoop.hbase.protobuf.generated.WALProtos.BulkLoadDescriptor bulkLoadDescriptor)
```
Create a bulk loader WALEdit

Parameters:
hri - The HRegionInfo for the region in which we are bulk loading
bulkLoadDescriptor - The descriptor for the Bulk Loader

Returns:
The WALEdit for the BulkLoad

getBulkLoadDescriptor

public static org.apache.hadoop.hbase.protobuf.generated.WALProtos.BulkLoadDescriptor getBulkLoadDescriptor(Cell cell)
                                                                                                     throws IOException

Deserialized and returns a BulkLoadDescriptor from the passed in Cell

Parameters:: cell - the key value
Returns:: deserialized BulkLoadDescriptor or null.
Throws:: IOException

Class WALEdit

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LOG

METAFAMILY

METAROW

COMPACTION

FLUSH

REGION_EVENT

BULK_LOAD

VERSION_2

isReplay

cells

EMPTY_WALEDIT

scopes

compressionContext

Constructor Detail

WALEdit

WALEdit

Method Detail

isMetaEditFamily

isMetaEditFamily

isMetaEdit

isReplay

setCompressionContext

add

isEmpty

size

getCells

setCells

getAndRemoveScopes

readFields

write

readFromCells

heapSize

toString

createFlushWALEdit

getFlushDescriptor

createRegionEventWALEdit

getRegionEventDescriptor

createCompaction

getRowForRegion

getCompaction

isCompactionMarker

createBulkLoadEvent

getBulkLoadDescriptor