com.bigdata.rwstore

Interface IHistoryManager

All Known Subinterfaces:

IMemoryManager, IRWStrategy, IStore

All Known Implementing Classes:

AllocationContext, MemoryManager, MemStrategy, RWStore, RWStrategy

public interface IHistoryManager

Interface for glue methods which permit the coordination of the hisory retention and deferred release mechanisms between the Journal, the IRWStrategy, and the backing IStore.

Author:

Bryan Thompson

Method Summary

Methods

Modifier and Type	Method and Description
int	checkDeferredFrees(AbstractJournal abstractJournal) This method is invoked during the commit protocol and gives the backing store an opportunity to check whether storage associated with deferred frees can now be released.
long	getLastReleaseTime() If history is retained this returns the time for which data was most recently released.
IRawTx	newTx() A hook used to support session protection by incrementing and decrementing a transaction counter within the IStore.
void	registerExternalCache(ConcurrentWeakValueCache<Long,ICommitter> historicalIndexCache, int byteCount) Call made from AbstractJournal to register the cache used.
long	saveDeferrals() Saves the current list of delete blocks, returning the address allocated.

Method Detail

newTx

IRawTx newTx()

A hook used to support session protection by incrementing and decrementing a transaction counter within the IStore. As long as a transaction is active we can not release data which is currently marked as freed but was committed at the point the session started.

saveDeferrals

long saveDeferrals()

Saves the current list of delete blocks, returning the address allocated. This can be used later to retrieve the addresses of allocations to be freed.

Writes the content of currentTxnFreeList to the store.

These are the current buffered frees that have yet been saved into a block referenced from the deferredFreeList

Returns:

the address of the deferred addresses saved on the store, or zero if none.

See Also:

DeleteBlockCommitter

checkDeferredFrees

int checkDeferredFrees(AbstractJournal abstractJournal)

This method is invoked during the commit protocol and gives the backing store an opportunity to check whether storage associated with deferred frees can now be released. The backing store needs to reply the deferred free blocks for the commit points that will be released, mark those addresses as free, and free the logged delete blocks.

Returns:

number of addresses freed

See Also:

AbstractJournal#commitNow()

registerExternalCache

void registerExternalCache(ConcurrentWeakValueCache<Long,ICommitter> historicalIndexCache,
                         int byteCount)

Call made from AbstractJournal to register the cache used. This can then be accessed to clear entries when storage is made available for re-cycling.

Note: It is not safe to clear at the point of the delete request since the data could still be loaded if the data is retained for a period due to a non-zero retention period or session protection.

Parameters:

externalCache - - used by the Journal to cache historical BTree references

dataSize - - the size of the checkpoint data (fixed for any version)

getLastReleaseTime

long getLastReleaseTime()

If history is retained this returns the time for which data was most recently released. No request can be made for data earlier than this.

Returns:

latest data release time