Added support for Solr's MoreLikeThis query handler (#730)

- When turned on, this adds MoreLikeThis support for sharded indexes in SolrCloud.
- Note that the MoreLikeThis component remains the default setting, as it provides more nuanced results as of this writing.
- Resolves VUFIND-652.

config/vufind/searches.ini

@@ -606,3 +606,18 @@ view=full
 ; Priority order (descending) for record sources (record ID prefixes separated
 ; from the actual record by period, e.g. testsrc.12345)
 ;sources = alli,testsrc
+
+; This section defines settings used to fetch similar records.
+[MoreLikeThis]
+; Boolean value indicating whether the newer MoreLikeThis query handler should be
+; used instead of the traditional MoreLikeThis component (default). Only the
+; MoreLikeThis query handler supports sharded indexes, but as of this writing, the
+; traditional component offers more nuanced relevance ranking. Results from these
+; methods may differ.
+;useMoreLikeThisHandler = true
+; If the MoreLikeThis handler is used, this setting can be used to adjust its
+; behavior. See https://cwiki.apache.org/confluence/display/solr/Other+Parsers#OtherParsers-MoreLikeThisQueryParser
+; for more information regarding the possible parameters.
+;params = "qf=title,title_short,callnumber-label,topic,language,author,publishDate mintf=1 mindf=1";
+; This setting can be used to limit the maximum number of suggestions. Default is 5.
+;count = 5

module/VuFind/src/VuFind/Search/Factory/AbstractSolrBackendFactory.php

@@ -42,6 +42,7 @@ use VuFind\Search\Solr\HierarchicalFacetListener;
 use VuFindSearch\Backend\BackendInterface;
 use VuFindSearch\Backend\Solr\LuceneSyntaxHelper;
 use VuFindSearch\Backend\Solr\QueryBuilder;
+use VuFindSearch\Backend\Solr\SimilarBuilder;
 use VuFindSearch\Backend\Solr\HandlerMap;
 use VuFindSearch\Backend\Solr\Connector;
 use VuFindSearch\Backend\Solr\Backend;
@@ -156,6 +157,7 @@ abstract class AbstractSolrBackendFactory implements FactoryInterface
     {
         $backend = new Backend($connector);
         $backend->setQueryBuilder($this->createQueryBuilder());
+        $backend->setSimilarBuilder($this->createSimilarBuilder());
         if ($this->logger) {
             $backend->setLogger($this->logger);
         }
@@ -372,6 +374,18 @@ abstract class AbstractSolrBackendFactory implements FactoryInterface
         return $builder;
     }
 
+    /**
+     * Create the similar records query builder.
+     *
+     * @return SimilarBuilder
+     */
+    protected function createSimilarBuilder()
+    {
+        return new SimilarBuilder(
+            $this->config->get($this->searchConfig), $this->uniqueKey
+        );
+    }
+
     /**
      * Load the search specs.
      *

module/VuFindSearch/src/VuFindSearch/Backend/Solr/Backend.php

@@ -73,6 +73,13 @@ class Backend extends AbstractBackend
      */
     protected $queryBuilder = null;
 
+    /**
+     * Similar records query builder.
+     *
+     * @var SimilarBuilder
+     */
+    protected $similarBuilder = null;
+
     /**
      * Constructor.
      *
@@ -211,6 +218,7 @@ class Backend extends AbstractBackend
         $params = $params ?: new ParamBag();
         $this->injectResponseWriter($params);
 
+        $params->mergeWith($this->getSimilarBuilder()->build($id, $params));
         $response   = $this->connector->similar($id, $params);
         $collection = $this->createRecordCollection($response);
         $this->injectSourceIdentifier($collection);
@@ -304,6 +312,33 @@ class Backend extends AbstractBackend
         return $this->queryBuilder;
     }
 
+    /**
+     * Set the similar records query builder.
+     *
+     * @param SimilarBuilder $similarBuilder Similar builder
+     *
+     * @return void
+     */
+    public function setSimilarBuilder(SimilarBuilder $similarBuilder)
+    {
+        $this->similarBuilder = $similarBuilder;
+    }
+
+    /**
+     * Return similar records query builder.
+     *
+     * Lazy loads an empty default SimilarBuilder if none was set.
+     *
+     * @return SimilarBuilder
+     */
+    public function getSimilarBuilder()
+    {
+        if (!$this->similarBuilder) {
+            $this->similarBuilder = new SimilarBuilder();
+        }
+        return $this->similarBuilder;
+    }
+
     /**
      * Return the record collection factory.
      *

module/VuFindSearch/src/VuFindSearch/Backend/Solr/Connector.php

@@ -185,23 +185,20 @@ class Connector implements \Zend\Log\LoggerAwareInterface
     /**
      * Return records similar to a given record specified by id.
      *
-     * Uses MoreLikeThis Request Handler
+     * Uses MoreLikeThis Request Component or MoreLikeThis Handler
      *
-     * @param string   $id     Id of given record
+     * @param string   $id     ID of given record (not currently used, but
+     * retained for backward compatibility / extensibility).
      * @param ParamBag $params Parameters
      *
      * @return string
+     *
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
      */
-    public function similar($id, ParamBag $params = null)
+    public function similar($id, ParamBag $params)
     {
-        $params = $params ?: new ParamBag();
-        $params
-            ->set('q', sprintf('%s:"%s"', $this->uniqueKey, addcslashes($id, '"')));
-        $params->set('qt', 'morelikethis');
-
         $handler = $this->map->getHandler(__FUNCTION__);
         $this->map->prepare(__FUNCTION__, $params);
-
         return $this->query($handler, $params);
     }
 

module/VuFindSearch/src/VuFindSearch/Backend/Solr/SimilarBuilder.php

+<?php
+
+/**
+ * SOLR SimilarBuilder.
+ *
+ * PHP version 5
+ *
+ * Copyright (C) Villanova University 2010.
+ * Copyright (C) The National Library of Finland 2016.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * @category VuFind
+ * @package  Search
+ * @author   Andrew S. Nagy <vufind-tech@lists.sourceforge.net>
+ * @author   David Maus <maus@hab.de>
+ * @author   Demian Katz <demian.katz@villanova.edu>
+ * @author   Ere Maijala <ere.maijala@helsinki.fi>
+ * @license  http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link     https://vufind.org
+ */
+namespace VuFindSearch\Backend\Solr;
+
+use VuFindSearch\ParamBag;
+
+/**
+ * SOLR SimilarBuilder.
+ *
+ * @category VuFind
+ * @package  Search
+ * @author   Andrew S. Nagy <vufind-tech@lists.sourceforge.net>
+ * @author   David Maus <maus@hab.de>
+ * @author   Demian Katz <demian.katz@villanova.edu>
+ * @author   Ere Maijala <ere.maijala@helsinki.fi>
+ * @license  http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link     https://vufind.org
+ */
+class SimilarBuilder implements SimilarBuilderInterface
+{
+    /**
+     * Solr field used to store unique identifier
+     *
+     * @var string
+     */
+    protected $uniqueKey;
+
+    /**
+     * Whether to use MoreLikeThis Handler instead of the traditional MoreLikeThis
+     * component.
+     *
+     * @var bool
+     */
+    protected $useHandler = false;
+
+    /**
+     * MoreLikeThis Handler parameters
+     *
+     * @var string
+     */
+    protected $handlerParams = '';
+
+    /**
+     * Number of similar records to retrieve
+     *
+     * @var int
+     */
+    protected $count = 5;
+
+    /**
+     * Constructor.
+     *
+     * @param \Zend\Config\Config $searchConfig Search config
+     * @param string              $uniqueKey    Solr field used to store unique
+     * identifier
+     *
+     * @return void
+     */
+    public function __construct(\Zend\Config\Config $searchConfig = null,
+        $uniqueKey = 'id'
+    ) {
+        $this->uniqueKey = $uniqueKey;
+        if (isset($searchConfig->MoreLikeThis)) {
+            $mlt = $searchConfig->MoreLikeThis;
+            if (isset($mlt->useMoreLikeThisHandler)
+                && $mlt->useMoreLikeThisHandler
+            ) {
+                $this->useHandler = true;
+                $this->handlerParams = isset($mlt->params) ? $mlt->params : '';
+            }
+            if (isset($mlt->count)) {
+                $this->count = $mlt->count;
+            }
+        }
+    }
+
+    /// Public API
+
+    /**
+     * Return SOLR search parameters based on a record Id and params.
+     *
+     * @param string $id Record Id
+     *
+     * @return ParamBag
+     */
+    public function build($id)
+    {
+        $params = new ParamBag();
+        if ($this->useHandler) {
+            $mltParams = $this->handlerParams
+                ? $this->handlerParams
+                : 'qf=title,title_short,callnumber-label,topic,language,author,'
+                    . 'publishDate mintf=1 mindf=1';
+            $params->set('q', sprintf('{!mlt %s}%s', $mltParams, $id));
+        } else {
+            $params->set(
+                'q', sprintf('%s:"%s"', $this->uniqueKey, addcslashes($id, '"'))
+            );
+            $params->set('qt', 'morelikethis');
+        }
+        if (null === $params->get('rows')) {
+            $params->set('rows', $this->count);
+        }
+        return $params;
+    }
+}

module/VuFindSearch/src/VuFindSearch/Backend/Solr/SimilarBuilderInterface.php

+<?php
+
+/**
+ * SOLR SimilarBuilder interface definition.
+ *
+ * PHP version 5
+ *
+ * Copyright (C) Villanova University 2010.
+ * Copyright (C) The National Library of Finland 2016.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * @category VuFind
+ * @package  Search
+ * @author   Andrew S. Nagy <vufind-tech@lists.sourceforge.net>
+ * @author   David Maus <maus@hab.de>
+ * @author   Demian Katz <demian.katz@villanova.edu>
+ * @author   Ere Maijala <ere.maijala@helsinki.fi>
+ * @license  http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link     https://vufind.org
+ */
+namespace VuFindSearch\Backend\Solr;
+
+use VuFindSearch\ParamBag;
+
+/**
+ * SOLR SimilarBuilder interface definition.
+ *
+ * @category VuFind
+ * @package  Search
+ * @author   Andrew S. Nagy <vufind-tech@lists.sourceforge.net>
+ * @author   David Maus <maus@hab.de>
+ * @author   Demian Katz <demian.katz@villanova.edu>
+ * @author   Ere Maijala <ere.maijala@helsinki.fi>
+ * @license  http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link     https://vufind.org
+ */
+interface SimilarBuilderInterface
+{
+    /**
+     * Build SOLR query based on VuFind query object.
+     *
+     * @param string $id Record id
+     *
+     * @return ParamBag
+     */
+    public function build($id);
+}

module/VuFindSearch/tests/unit-tests/src/VuFindTest/Backend/Solr/SimilarBuilderTest.php

+<?php
+
+/**
+ * Unit tests for SOLR similar records query builder
+ *
+ * PHP version 5
+ *
+ * Copyright (C) Villanova University 2010.
+ * Copyright (C) The National Library of Finland 2016.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * @category VuFind
+ * @package  Search
+ * @author   David Maus <maus@hab.de>
+ * @author   Ere Maijala <ere.maijala@helsinki.fi>
+ * @license  http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link     https://vufind.org
+ */
+namespace VuFindTest\Backend\Solr;
+
+use VuFindSearch\Backend\Solr\SimilarBuilder;
+
+/**
+ * Unit tests for SOLR similar records query builder
+ *
+ * @category VuFind
+ * @package  Search
+ * @author   David Maus <maus@hab.de>
+ * @author   Ere Maijala <ere.maijala@helsinki.fi>
+ * @license  http://opensource.org/licenses/gpl-2.0.php GNU General Public License
+ * @link     https://vufind.org
+ */
+class SimilarBuilderTest extends \VuFindTest\Unit\TestCase
+{
+    /**
+     * Test builder with default params.
+     *
+     * @return void
+     */
+    public function testDefaultParams()
+    {
+        $sb = new SimilarBuilder();
+        $response = $sb->build('testrecord');
+        $rows = $response->get('rows');
+        $this->assertEquals(5, $rows[0]);
+        $q = $response->get('q');
+        $this->assertEquals('id:"testrecord"', $q[0]);
+        $qt = $response->get('qt');
+        $this->assertEquals('morelikethis', $qt[0]);
+    }
+
+    /**
+     * Test builder with alternative id field.
+     *
+     * @return void
+     */
+    public function testAlternativeIdField()
+    {
+        $sb = new SimilarBuilder(null, 'key');
+        $response = $sb->build('testrecord');
+        $q = $response->get('q');
+        $this->assertEquals('key:"testrecord"', $q[0]);
+    }
+
+    /**
+     * Test builder with different configurations.
+     *
+     * @return void
+     */
+    public function testMltConfig()
+    {
+        $config = [
+            'MoreLikeThis' => [
+                'count' => 10
+            ]
+        ];
+        $sb = new SimilarBuilder(new \Zend\Config\Config($config));
+        $response = $sb->build('testrecord');
+        $rows = $response->get('rows');
+        $this->assertEquals(10, $rows[0]);
+
+        $config['MoreLikeThis']['useMoreLikeThisHandler'] = true;
+        $sb = new SimilarBuilder(new \Zend\Config\Config($config));
+        $response = $sb->build('testrecord');
+        $rows = $response->get('rows');
+        $this->assertEquals(10, $rows[0]);
+        $q = $response->get('q');
+        $this->assertEquals(
+            '{!mlt qf=title,title_short,callnumber-label,topic,language,author,'
+            . 'publishDate mintf=1 mindf=1}testrecord',
+            $q[0]
+        );
+        $qt = $response->get('qt');
+        $this->assertEquals(null, $qt);
+
+        $config['MoreLikeThis']['params'] = 'qf=title,topic';
+        $sb = new SimilarBuilder(new \Zend\Config\Config($config));
+        $response = $sb->build('testrecord');
+        $q = $response->get('q');
+        $this->assertEquals('{!mlt qf=title,topic}testrecord', $q[0]);
+    }
+}