[WIP] Add EmbeddedQueryResultCache

Most of the job is already done by the `EmbeddedQueryDependencyLinksStore`
to track and update query dependencies.

To eliminate necessary SQL/SPARQL connections `EmbeddedQueryResultCache` ought to
cache a subject list returned from the `QueryEngine`.

We don't cache the string result of a printer == it means we don't
interfere with how the printer manipulates the data, `EmbeddedQueryResultCache` as
the name suggests caches the return object (aka `QueryResult`) from
the QueryEngine before it is forwarded to an individual printer.

If for some reason `EmbeddedQueryDependencyLinksStore` is not enabled then
auto-invalidation of the `EmbeddedQueryResultCache` can not occur but instead
(same as of now == manual intervention using the purge button) setting
`$GLOBALS['smwgEmbeddedQueryResultCacheRefreshOnPurge'] = true;` can
be used to emit a purge action event to invalidate all query cache items stored
with the corresponding article (aka subject).

`$GLOBALS['smwgEmbeddedQueryResultCacheLifetime'] = 60 * 60 * 24; // a day` declares the lifetime
of a cached item

SemanticMediaWiki.settings.php

@@ -881,7 +881,7 @@
 # @since 2.3 (experimental)
 # @default false
 ##
-$GLOBALS['smwgEnabledQueryDependencyLinksStore'] = false;
+$GLOBALS['smwgEnabledQueryDependencyLinksStore'] = true;
 ##
 
 ###
@@ -900,9 +900,51 @@
 $GLOBALS['smwgPropertyDependencyDetectionBlacklist'] = array( '_MDAT', '_SOBJ' );
 ##
 
+###
+# This stores subjects that were fetched from the QueryEngine (not the string result
+# generated from a result printer) and allows to improve general page-loading time
+# for articles that contain embedded queries and decrease server load on query requests
+# due to subject list (as to the answer of the query) being served from cache
+# instead of running a live DB/SPARQL query.
+#
+# It is suggested that `smwgEnabledQueryDependencyLinksStore` is enabled to make
+# use of the automatic query results update (and hereof the invalidation of the
+# cache).
+#
+# CACHE_NONE as default means that this feature is disabled
+#
+# @since 2.4 (experimental)
+#
+# @default: CACHE_NONE, users need to actively enable it in order
+# to make use of it
+##
+$GLOBALS['smwgEmbeddedQueryResultCacheType'] = CACHE_NONE;
+##
+
+###
+# Declares the lifetime of a cached item for when `smwgEmbeddedQueryResultCacheType`
+# is enabled.
+#
+# @since 2.4
+##
+$GLOBALS['smwgEmbeddedQueryResultCacheLifetime'] = 60 * 60 * 24; // a day
+##
+
+###
+# If `smwgEnabledQueryDependencyLinksStore` is enabled this setting is not required
+# as results are expected to be automatically purged. In case it is disabled and
+# a user still wants to take advantage of the cache then it is suggested to enable
+# this setting so that results are refreshed (or better the cache is going to be
+# invalidated) by force on an article purge event.
+#
+# @since 2.4
+##
+$GLOBALS['smwgEmbeddedQueryResultCacheRefreshOnPurge'] = false;
+##
+
 ###
 # The setting is introduced the keep backwards compatibility with existing Rdf/Turtle
-# exports. The `aux` marker is epxected only used to be used for selected properties
+# exports. The `aux` marker is expected to be used only for selected properties
 # to generate a helper value and not for any other predefined property.
 #
 # Any property that does not explicitly require an auxiliary value (such `_dat`/

includes/Settings.php

@@ -122,6 +122,9 @@ public static function newFromGlobals() {
 			'smwgValueLookupCacheType' => $GLOBALS['smwgValueLookupCacheType'],
 			'smwgValueLookupCacheLifetime' => $GLOBALS['smwgValueLookupCacheLifetime'],
 			'smwgValueLookupFeatures' => $GLOBALS['smwgValueLookupFeatures'],
+			'smwgEmbeddedQueryResultCacheType' => $GLOBALS['smwgEmbeddedQueryResultCacheType'],
+			'smwgEmbeddedQueryResultCacheLifetime' => $GLOBALS['smwgEmbeddedQueryResultCacheLifetime'],
+			'smwgEmbeddedQueryResultCacheRefreshOnPurge' => $GLOBALS['smwgEmbeddedQueryResultCacheRefreshOnPurge'],
 			'smwgFixedProperties' => $GLOBALS['smwgFixedProperties'],
 			'smwgPropertyLowUsageThreshold' => $GLOBALS['smwgPropertyLowUsageThreshold'],
 			'smwgPropertyZeroCountDisplay' => $GLOBALS['smwgPropertyZeroCountDisplay'],

includes/storage/SMW_QueryResult.php

@@ -61,6 +61,11 @@ class SMWQueryResult {
 	 */
 	private $countValue;
 
+	/**
+	 * @var boolean
+	 */
+	private $isFromCache = false;
+
 	/**
 	 * Initialise the object with an array of SMWPrintRequest objects, which
 	 * define the structure of the result "table" (one for each column).
@@ -208,6 +213,24 @@ public function getCountValue() {
 		return $this->countValue;
 	}
 
+	/**
+	 * @since  2.4
+	 *
+	 * @param boolean $isFromCache
+	 */
+	public function setFromCache( $isFromCache ) {
+		$this->isFromCache = (bool)$isFromCache;
+	}
+
+	/**
+	 * @since  2.4
+	 *
+	 * @return boolean
+	 */
+	public function isFromCache() {
+		return $this->isFromCache;
+	}
+
 	/**
 	 * Return error array, possibly empty.
 	 *

includes/storage/SMW_Store.php

@@ -215,6 +215,7 @@ public function updateData( SemanticData $semanticData ) {
 		/**
 		 * @since 1.6
 		 */
+		wfRunHooks( 'SMW::Store::BeforeDataUpdateComplete', array( $this, $semanticData ) );
 		wfRunHooks( 'SMWStore::updateDataBefore', array( $this, $semanticData ) );
 
 		// Invalidate the page, so data stored on it gets displayed immediately in queries.
@@ -232,6 +233,7 @@ public function updateData( SemanticData $semanticData ) {
 		 * @since 1.6
 		 */
 		wfRunHooks( 'SMWStore::updateDataAfter', array( $this, $semanticData ) );
+		wfRunHooks( 'SMW::Store::AfterDataUpdateComplete', array( $this, $semanticData ) );
 	}
 
 	/**

includes/storage/SQLStore/SMW_SQLStore3.php

@@ -367,7 +367,7 @@ public function getQueryResult( SMWQuery $query ) {
 
 		$result = null;
 
-		if ( wfRunHooks( 'SMW::Store::BeforeQueryResultLookupComplete', array( $this, $query, &$result ) ) ) {
+		if ( wfRunHooks( 'SMW::Store::BeforeQueryResultLookupComplete', array( $this, $query, &$result, $this->factory->newSlaveQueryEngine() ) ) ) {
 			$result = $this->fetchQueryResult( $query );
 		}
 

src/CacheFactory.php

@@ -3,6 +3,7 @@
 namespace SMW;
 
 use Onoi\Cache\CacheFactory as OnoiCacheFactory;
+use Onoi\BlobStore\BlobStore;
 use SMW\ApplicationFactory;
 use ObjectCache;
 use RuntimeException;
@@ -127,4 +128,85 @@ public function newMediaWikiCompositeCache( $mediaWikiCacheType = null ) {
 		return $compositeCache;
 	}
 
+	/**
+	 * @since 2.3
+	 *
+	 * @param integer|string $mbeddedQueryResultCacheType
+	 * @param integer $embeddedQueryResultCacheLifetime
+	 *
+	 * @return BlobStore
+	 */
+	public function newEmbeddedQueryResultBlobstore( $embeddedQueryResultCacheType = null, $embeddedQueryResultCacheLifetime = 3600 ) {
+
+		$blobStore = new BlobStore(
+			'smw:qrc:store',
+			$this->newMediaWikiCompositeCache( $embeddedQueryResultCacheType )
+		);
+
+		// If CACHE_NONE is selected, disable the usage
+		$blobStore->setUsageState(
+			$embeddedQueryResultCacheType !== CACHE_NONE
+		);
+
+		$blobStore->setExpiryInSeconds(
+			$embeddedQueryResultCacheLifetime
+		);
+
+		$blobStore->setNamespacePrefix(
+			$this->getCachePrefix()
+		);
+
+		return $blobStore;
+	}
+
+	/**
+	 * @since 2.4
+	 *
+	 * @return EmbeddedQueryResultCache
+	 */
+	public function newEmbeddedQueryResultCache( $embeddedQueryResultCacheType = null, $embeddedQueryResultCacheLifetime = 3600 ) {
+
+		$embeddedQueryResultBlobstore = $this->newEmbeddedQueryResultBlobstore(
+			$embeddedQueryResultCacheType,
+			$embeddedQueryResultCacheLifetime
+		);
+
+		$embeddedQueryResultCache = new EmbeddedQueryResultCache(
+			$embeddedQueryResultBlobstore
+		);
+
+		return $embeddedQueryResultCache;
+	}
+
+	/**
+	 * @since 2.3
+	 *
+	 * @param integer|string $mediaWikiCacheType
+	 * @param integer $valueLookupCacheLifetime
+	 *
+	 * @return BlobStore
+	 */
+	public function newValueLookupBlobstore( $valueLookupCacheType = null, $valueLookupCacheLifetime = 3600 ) {
+
+		$blobStore = new BlobStore(
+			'smw:vl:store',
+			$this->newMediaWikiCompositeCache( $valueLookupCacheType )
+		);
+
+		// If CACHE_NONE is selected, disable the usage
+		$blobStore->setUsageState(
+			$valueLookupCacheType !== CACHE_NONE
+		);
+
+		$blobStore->setExpiryInSeconds(
+			$valueLookupCacheLifetime
+		);
+
+		$blobStore->setNamespacePrefix(
+			$this->getCachePrefix()
+		);
+
+		return $blobStore;
+	}
+
 }