SMWDIHandlerBlob Class Reference

Inheritance diagram for SMWDIHandlerBlob:

Collaboration diagram for SMWDIHandlerBlob:

Public Member Functions
	getTableFields ()
	getFetchFields ()
	getTableIndexes ()
	getWhereConds (SMWDataItem $dataItem)
	getInsertValues (SMWDataItem $dataItem)
	getIndexField ()
	getLabelField ()
	dataItemFromDBKeys ($dbkeys)
Public Member Functions inherited from SMWDataItemHandler
	__construct (SMWSQLStore3 $store)
	getTableFields ()
	getFetchFields ()
	getTableIndexes ()
	getWhereConds (SMWDataItem $dataItem)
	getInsertValues (SMWDataItem $dataItem)
	getIndexField ()
	getLabelField ()
	dataItemFromDBKeys ($dbkeys)

Public Attributes
const	MAX_HASH_LENGTH = 72

Static Protected Member Functions
static	makeHash ($string)

Additional Inherited Members
Protected Attributes inherited from SMWDataItemHandler
	$store

Detailed Description

This class implements Store access to blob (string) data items.

Since

1.8

Author

Nischay Nahata

Member Function Documentation

SMWDIHandlerBlob::dataItemFromDBKeys

(

$dbkeys

)

See Also

SMWDataItemHandler::dataItemFromDBKeys()

Since

1.8

Parameters

array | string

$dbkeys

expecting array here

Returns

SMWDataItem

SMWDIHandlerBlob::getFetchFields

(

)

See Also

SMWDataItemHandler::getFetchFields()

Since

1.8

Returns

array

SMWDIHandlerBlob::getIndexField

(

)

Method to return the field used to select this type of DataItem

Since

1.8

Returns

string

SMWDIHandlerBlob::getInsertValues

(

SMWDataItem

$dataItem

)

Method to return an array of fields=>values for a DataItem This array is used to perform all insert operations into the DB To optimize return minimum fields having indexes

Returns

array

SMWDIHandlerBlob::getLabelField

(

)

Method to return the field used to select this type of DataItem using the label

Since

1.8

Returns

string

SMWDIHandlerBlob::getTableFields

(

)

Method to return array of fields for a DI type

Returns

array

SMWDIHandlerBlob::getTableIndexes

(

)

See Also

SMWDataItemHandler::getTableIndexes

Since

2.4

Returns

array

SMWDIHandlerBlob::getWhereConds

(

SMWDataItem

$dataItem

)

Method to return an array of fields=>values for a DataItem

Returns

array

static SMWDIHandlerBlob::makeHash (   $string )

staticprotected

Method to make a hashed representation for strings of length greater than self::MAX_HASH_LENGTH to be used for selecting and sorting.

Since

1.8

Parameters

$string

string

Returns

string

Member Data Documentation

const SMWDIHandlerBlob::MAX_HASH_LENGTH = 72

Maximal number of bytes (chars) to be stored in the hash field of the table. Must not be bigger than 255 (the length of our VARCHAR field in the DB). Strings that are longer than this will be stored as a blob, and the hash will only start with the original string but the last 32 bytes are used for a hash. So the minimal portion of the string that is stored literally in the hash is 32 chars less.

The value of 72 was chosen since it leads to a smaller index size at the cost of needing more blobs in cases where many strings are of length 73 to 255. But keeping the index small seems more important than saving disk space. Also, with 72 bytes there are at least 40 bytes of content available for sorting and prefix matching, which should be more than enough in most contexts.

Since

1.8

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

• /home/hwfunc/workspace/leonid/BlueSpiceDoc-composer/mediawiki-REL1_27/extensions/SemanticMediaWiki/includes/storage/SQLStore/SMW_DIHandler_Blob.php