Represents a cache for accesses to the the data cells within a Table. More...

Classes
class	DCCache
	An implementation of Cache. More...

struct	DCCacheKey
	Struct that creates an object that hashes nicely over the cache source. More...

Public Member Functions
void	AlterCacheDynamics (int maxCacheSize, int maxCellSize)
	Dynamically resizes the data cell cache so it can store more/less data. More...

void	Set (int tableKey, int row, int column, DataObject cell)
	Adds a DataObject on the cache for the given row/column of the table. More...

DataObject	Get (int tableKey, int row, int column)
	Gets a cell from the cache. More...

DataObject	Remove (int tableKey, int row, int column)
	Removes a cell from the cache. More...

void	Clear ()
	Completely wipe the cache of all entries. More...

Package Functions
	DataCellCache (SystemContext context, ICache systemCache, int maxCacheSize, int maxCellSize, int hashSize)
	Instantiate the DataCellCache. More...

	DataCellCache (SystemContext context, ICache systemCache, int maxCacheSize, int maxCellSize)

Static Package Functions
static int	ClosestPrime (int value)
	Returns a prime number from PRIME_LIST that is the closest prime greater or equal to the given value. More...

Properties
long	CurrentCacheSize `[get]`
	Returns an estimation of the current cache size in bytes. More...

Private Member Functions
void	ReduceCacheSize (long val)
	Evaluate the cache size by the given amount. More...

Static Private Member Functions
static int	AmountMemory (DataObject cell)
	Returns an approximation of the amount of memory taken by a given DataObject. More...

Private Attributes
readonly DCCache	cache
	The master cache. More...

readonly SystemContext	context
	The TransactionSystem that this cache is from. More...

long	currentCacheSize
	The current size of the cache. More...

int	maxCellSize
	The maximum size of a DataCell that is allowed to go in the cache. More...

Static Private Attributes
static readonly int[]	PRIME_LIST
	A list of primes ordered from lowest to highest. More...

Detailed Description

Represents a cache for accesses to the the data cells within a Table.

Whenever a column/row index to a cell is accessed, the cache is first checked. If the cell is not in the cache then it may go ahead and read the cell from the file.

Issue We may need to keep track of memory used. Since a String may use up much memory, we may need a cap on the maximum size the cache can grow to. For example, we wouldn't want to cache a large document. This could be handled at a higher level?

Definition at line 37 of file DataCellCache.cs.

Constructor & Destructor Documentation

Deveel.Data.Caching.DataCellCache.DataCellCache	(	SystemContext	context,
		ICache	systemCache,
		int	maxCacheSize,
		int	maxCellSize,
		int	hashSize
	)

inlinepackage

Instantiate the DataCellCache.

<param name="context></param> <param name="systemCache"></param> <param name="maxCacheSize">The maximum size in bytes that the cache is allowed to grow to (eg. 4000000).

Parameters

maxCellSize	The maximum size of an object that can be stored in the cache.
hashSize	The number of elements in the hash (should be a prime number).

Definition at line 109 of file DataCellCache.cs.

                                                                                                                            {
             this.context = context;
             this.maxCellSize = maxCellSize;
 
             cache = new DCCache(this, systemCache, hashSize, maxCacheSize);
         }

Deveel.Data.Caching.DataCellCache.DataCellCache	(	SystemContext	context,
		ICache	systemCache,
		int	maxCacheSize,
		int	maxCellSize
	)

inlinepackage

Definition at line 116 of file DataCellCache.cs.

             : this(context, systemCache, maxCacheSize, maxCellSize, 88547) {
             // Good prime number hash size
         }

Member Function Documentation

void Deveel.Data.Caching.DataCellCache.AlterCacheDynamics	(	int	maxCacheSize,
		int	maxCellSize
	)

inline

Dynamically resizes the data cell cache so it can store more/less data.

Parameters

maxCacheSize
maxCellSize

This is used to change cache dynamics at runtime.

Definition at line 140 of file DataCellCache.cs.

                                                                           {
             lock (this) {
                 this.maxCellSize = maxCellSize;
                 cache.SetCacheSize(maxCacheSize);
             }
         }

static int Deveel.Data.Caching.DataCellCache.AmountMemory ( DataObject cell )

inlinestaticprivate

Returns an approximation of the amount of memory taken by a given DataObject.

Parameters

cell

Returns

Definition at line 153 of file DataCellCache.cs.

                                                          {
             return 16 + cell.SizeOf();
         }

void Deveel.Data.Caching.DataCellCache.Clear ( )

inline

Completely wipe the cache of all entries.

Definition at line 234 of file DataCellCache.cs.

                             {
             lock (this) {
                 if (cache.NodeCount == 0 && currentCacheSize != 0) {
                     context.Logger.Error(this, "Assertion failed - if nodeCount = 0 then current_cache_size must also be 0.");
                 }
                 if (cache.NodeCount != 0) {
                     cache.Clear();
                     context.Stats.Increment(StatsDefaultKeys.DataCellCacheTotalWipes);
                 }
                 currentCacheSize = 0;
             }
         }

static int Deveel.Data.Caching.DataCellCache.ClosestPrime ( int value )

inlinestaticpackage

Returns a prime number from PRIME_LIST that is the closest prime greater or equal to the given value.

Parameters

value

Returns

Definition at line 263 of file DataCellCache.cs.

                                                     {
             for (int i = 0; i < PRIME_LIST.Length; ++i) {
                 if (PRIME_LIST[i] >= value) {
                     return PRIME_LIST[i];
                 }
             }
             // Return the last prime
             return PRIME_LIST[PRIME_LIST.Length - 1];
         }

DataObject Deveel.Data.Caching.DataCellCache.Get	(	int	tableKey,
		int	row,
		int	column
	)

inline

Gets a cell from the cache.

Parameters

tableKey
row
column

Returns: Returns the value of the cell at the given coordinates, or null if the row/column is not in the cache.

Definition at line 201 of file DataCellCache.cs.

                                                                  {
             lock (this) {
                 return (DataObject) cache.Get(new DCCacheKey(tableKey, (short) column, row));
             }
         }

void Deveel.Data.Caching.DataCellCache.ReduceCacheSize ( long val )

inlineprivate

Evaluate the cache size by the given amount.

Parameters

val

Definition at line 251 of file DataCellCache.cs.

                                                {
             currentCacheSize -= val;
         }

DataObject Deveel.Data.Caching.DataCellCache.Remove	(	int	tableKey,
		int	row,
		int	column
	)

inline

Removes a cell from the cache.

Parameters

tableKey
row
column

This is used when we need to notify the cache that an object has become outdated. This should be used when the cell has been removed or changed.

Returns: Returns the cell that was removed, or null if there was no cell at the given location.

Definition at line 222 of file DataCellCache.cs.

                                                                     {
             lock (this) {
                 var cell = (DataObject)cache.Remove(new DCCacheKey(tableKey, (short) column, row));
                 if (cell != null)
                     currentCacheSize -= AmountMemory(cell);
                 return cell;
             }
         }

void Deveel.Data.Caching.DataCellCache.Set	(	int	tableKey,
		int	row,
		int	column,
		DataObject	cell
	)

inline

Adds a DataObject on the cache for the given row/column of the table.

Parameters

tableKey
row
column
cell

Ignores any cells that are larger than the maximum size.

Definition at line 168 of file DataCellCache.cs.

                                                                             {
             lock (this) {
                 int memoryUse = AmountMemory(cell);
                 if (memoryUse <= maxCellSize) {
                     // Generate the key
                     var key = new DCCacheKey(tableKey, (short)column, row);
                     // If there is an existing object here, remove it from the cache and
                     // update the current_cache_size.
                     var removedCell = (DataObject)cache.Remove(key);
                     if (removedCell != null) {
                         currentCacheSize -= AmountMemory(removedCell);
                     }
                     // Put the new entry in the cache
                     cache.Set(key, cell);
                     currentCacheSize += memoryUse;
                 } else {
                     // If the object is larger than the minimum object size that can be
                     // cached, remove any existing entry (possibly smaller) from the cache.
                     Remove(tableKey, row, column);
                 }
             }
         }

Member Data Documentation

readonly DCCache Deveel.Data.Caching.DataCellCache.cache

private

The master cache.

Definition at line 81 of file DataCellCache.cs.

readonly SystemContext Deveel.Data.Caching.DataCellCache.context

private

The TransactionSystem that this cache is from.

Definition at line 86 of file DataCellCache.cs.

long Deveel.Data.Caching.DataCellCache.currentCacheSize

private

The current size of the cache.

Definition at line 91 of file DataCellCache.cs.

int Deveel.Data.Caching.DataCellCache.maxCellSize

private

The maximum size of a DataCell that is allowed to go in the cache.

Definition at line 96 of file DataCellCache.cs.

readonly int [] Deveel.Data.Caching.DataCellCache.PRIME_LIST

staticprivate

A list of primes ordered from lowest to highest.

Definition at line 41 of file DataCellCache.cs.

Property Documentation

long Deveel.Data.Caching.DataCellCache.CurrentCacheSize

get

Returns an estimation of the current cache size in bytes.

Definition at line 124 of file DataCellCache.cs.

The documentation for this class was generated from the following file:

/var/calculate/remote/distfiles/egit-src/deveeldb.git/src/deveeldb/Deveel.Data.Caching/DataCellCache.cs

Classes

Public Member Functions

Package Functions

Static Package Functions

Properties

Private Member Functions

Static Private Member Functions

Private Attributes

Static Private Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation

Property Documentation