org.apache.hadoop.hbase.regionserver

Interface MemStore

All Known Implementing Classes:

AbstractMemStore, CompactingMemStore, DefaultMemStore

@InterfaceAudience.Private
public interface MemStore

The MemStore holds in-memory modifications to the Store. Modifications are Cells.

The MemStore functions should not be called in parallel. Callers should hold write and read locks. This is done in HStore.

Method Summary

Modifier and Type	Method and Description
void	add(Cell cell, MemStoreSizing memstoreSizing) Write an update
void	add(Iterable<Cell> cells, MemStoreSizing memstoreSizing) Write the updates
void	clearSnapshot(long id) Clears the current snapshot of the Memstore.
MemStoreSize	getFlushableSize() Flush will first clear out the data in snapshot if any (It will take a second flush invocation to clear the current Cell set).
List<KeyValueScanner>	getScanners(long readPt)
MemStoreSize	getSnapshotSize() Return the size of the snapshot(s) if any
boolean	isSloppy()
long	preFlushSeqIDEstimation() This method is called before the flush is executed.
MemStoreSize	size()
MemStoreSnapshot	snapshot() Creates a snapshot of the current memstore.
default void	startReplayingFromWAL() This message intends to inform the MemStore that next coming updates are going to be part of the replaying edits from WAL
default void	stopReplayingFromWAL() This message intends to inform the MemStore that the replaying edits from WAL are done
long	timeOfOldestEdit()
void	upsert(Iterable<Cell> cells, long readpoint, MemStoreSizing memstoreSizing) Update or insert the specified cells.

Method Detail

snapshot

MemStoreSnapshot snapshot()

Creates a snapshot of the current memstore. Snapshot must be cleared by call to clearSnapshot(long).

Returns:

MemStoreSnapshot

clearSnapshot

void clearSnapshot(long id)
            throws UnexpectedStateException

Clears the current snapshot of the Memstore.

Parameters:

id -

Throws:

UnexpectedStateException

See Also:

snapshot()

getFlushableSize

MemStoreSize getFlushableSize()

Flush will first clear out the data in snapshot if any (It will take a second flush invocation to clear the current Cell set). If snapshot is empty, current Cell set will be flushed.

Returns:

On flush, how much memory we will clear.

getSnapshotSize

MemStoreSize getSnapshotSize()

Return the size of the snapshot(s) if any

Returns:

size of the memstore snapshot

add

void add(Cell cell,
         MemStoreSizing memstoreSizing)

Write an update

Parameters:

cell -

memstoreSizing - The delta in memstore size will be passed back via this. This will include both data size and heap overhead delta.

add

void add(Iterable<Cell> cells,
         MemStoreSizing memstoreSizing)

Write the updates

Parameters:

cells -

memstoreSizing - The delta in memstore size will be passed back via this. This will include both data size and heap overhead delta.

timeOfOldestEdit

long timeOfOldestEdit()

Returns:

Oldest timestamp of all the Cells in the MemStore

upsert

void upsert(Iterable<Cell> cells,
            long readpoint,
            MemStoreSizing memstoreSizing)

Update or insert the specified cells.

For each Cell, insert into MemStore. This will atomically upsert the value for that row/family/qualifier. If a Cell did already exist, it will then be removed.

Currently the memstoreTS is kept at 0 so as each insert happens, it will be immediately visible. May want to change this so it is atomic across all KeyValues.

This is called under row lock, so Get operations will still see updates atomically. Scans will only see each KeyValue update as atomic.

Parameters:

cells -

readpoint - readpoint below which we can safely remove duplicate Cells.

memstoreSizing - The delta in memstore size will be passed back via this. This will include both data size and heap overhead delta.

getScanners

List<KeyValueScanner> getScanners(long readPt)
                           throws IOException

Returns:

scanner over the memstore. This might include scanner over the snapshot when one is present.

Throws:

IOException

size

MemStoreSize size()

Returns:

Total memory occupied by this MemStore. This won't include any size occupied by the snapshot. We assume the snapshot will get cleared soon. This is not thread safe and the memstore may be changed while computing its size. It is the responsibility of the caller to make sure this doesn't happen.

preFlushSeqIDEstimation

long preFlushSeqIDEstimation()

This method is called before the flush is executed.

Returns:

an estimation (lower bound) of the unflushed sequence id in memstore after the flush is executed. if memstore will be cleared returns HConstants.NO_SEQNUM.

isSloppy

boolean isSloppy()

startReplayingFromWAL

default void startReplayingFromWAL()

This message intends to inform the MemStore that next coming updates are going to be part of the replaying edits from WAL

stopReplayingFromWAL

default void stopReplayingFromWAL()

This message intends to inform the MemStore that the replaying edits from WAL are done