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<?php
namespace SMW\SQLStore\EntityStore;
use SMW\SQLStore\SQLStore;
use SMWDataItem as DataItem;
/**
* Classes extending this represent all store layout that is known about a certain dataitem
*
* @license GNU GPL v2+
* @since 1.8
*
* @author Nischay Nahata
*/
abstract class DataItemHandler {
/**
* @var SQLStore
*/
protected $store;
/**
* @var integer
*/
protected $fieldTypeFeatures = false;
/**
* @var null|string
*/
private $dbType;
/**
* @since 1.8
*
* @param SQLStore $store
*/
public function __construct( SQLStore $store ) {
$this->store = $store;
}
/**
* @since 3.0
*
* @param integer $fieldTypeFeatures
*/
public function setFieldTypeFeatures( $fieldTypeFeatures ) {
$this->fieldTypeFeatures = $fieldTypeFeatures;
}
/**
* @since 3.0
*
* @param integer $feature
*
* @return boolean
*/
public function isEnabledFeature( $feature ) {
return ( (int)$this->fieldTypeFeatures & $feature ) != 0;
}
/**
* @since 3.0
*
* @param boolean
*/
public function isDbType( $dbType ) {
if ( $this->dbType === null ) {
$this->dbType = $this->store->getConnection( 'mw.db' )->getType();
}
return $this->dbType === $dbType;
}
/**
* Return array of fields for a DI type.
*
* Tables declare value columns ("object fields") by specifying their
* name and type. Types are given using letters:
* - t for strings of the same maximal length as MediaWiki title names,
* - l for arbitrarily long strings; searching/sorting with such data
* may be limited for performance reasons,
* - w for strings as used in MediaWiki for encoding interwiki prefixes
* - n for namespace numbers (or other similar integers)
* - f for floating point numbers of double precision
* - p for a reference to an SMW ID as stored in the SMW IDs table;
* this corresponds to a data entry of ID "tnwt".
*
* @since 1.8
* @return array
*/
abstract public function getTableFields();
/**
* Return an array with all the field names and types that need to be
* retrieved from the database in order to create a dataitem using
* dataItemFromDBKeys(). The result format is the same as for
* getTableFields(), but usually with fewer field names.
*
* @note In the future, we will most likely use a method that return
* only a single field name. Currently, we still need an array for
* concepts.
*
* @since 1.8
* @return array
*/
abstract public function getFetchFields();
/**
* Return an array of additional indexes that should be provided for
* the table using this DI handler. By default, SMWSQLStore3 will
* already create indexes for all standard select operations, based
* on the indexfield provided by getIndexField(). Hence, most handlers
* do not need to define any indexes.
*
* @since 1.8
* @return array
*/
public function getTableIndexes() {
return [];
}
/**
* Provides a possibility to return a specific index hint for a domain.
*
* @since 3.0
*
* @param string $key
*
* @return string
*/
public function getIndexHint( $key ) {
return '';
}
/**
* Return an array of fields=>values to conditions (WHERE part) in SQL
* queries for the given DataItem. This method can return fewer
* fields than getInstertValues as long as they are enough to identify
* an item for search.
*
* @since 1.8
* @param DataItem $dataItem
* @return array
*/
abstract public function getWhereConds( DataItem $dataItem );
/**
* Return an array of fields=>values that is to be inserted when
* writing the given DataItem to the database. Values should be set
* for all columns, even if NULL. This array is used to perform all
* insert operations into the DB.
*
* @since 1.8
* @param DataItem $dataItem
* @return array
*/
abstract public function getInsertValues( DataItem $dataItem );
/**
* Return the field used to select this type of DataItem. In
* particular, this identifies the column that is used to sort values
* of this kind. Every type of data returns a non-empty string here.
*
* @since 1.8
* @return string
*/
abstract public function getIndexField();
/**
* Return the label field for this type of DataItem. This should be
* a string column in the database table that can be used for selecting
* values using criteria such as "starts with". The return value can be
* empty if this is not supported. This is preferred for DataItem
* classes that do not have an obvious canonical string writing anyway.
*
* The return value can be a column name or the empty string (if the
* give type of DataItem does not have a label field).
*
* @since 1.8
* @return string
*/
abstract public function getLabelField();
/**
* Returns the expected sort field.
*
* @since 3.0
*
* @return string
*/
public function getSortField() {
return '';
}
/**
* Create a dataitem from an array of DB keys or a single DB key
* string. May throw an DataItemException if the given DB keys
* cannot be converted back into a dataitem. Each implementation
* of this method must otherwise run without errors for both array
* and string inputs.
*
* @since 1.8
* @param array|string $dbkeys
* @throws DataItemException
* @return DataItem
*/
abstract public function dataItemFromDBKeys( $dbkeys );
}
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