HSEARCH-2613 Use enum IndexScope

which allows to clarify the implementation of different workflows.

In particular, it clarifies that the parameter `maxResultsPerEntity`
is not only used in customized index scopes (CRITERIA, HQL), but
also used in the full index scope (FULL_ENTITY).

jsr352/core/src/main/java/org/hibernate/search/jsr352/massindexing/impl/steps/lucene/EntityReader.java

@@ -223,28 +223,28 @@ public void open(Serializable checkpointId) throws Exception {
 		session = PersistenceUtil.openSession( emf, tenantId );
 		sessionFactory = emf.unwrap( SessionFactory.class );
 
-		PartitionContextData partitionData = null;
-		// HQL approach
-		// In this approach, the checkpoint mechanism is disabled, because we
-		// don't know if the selection is ordered by ID ascendingly in the query.
-		if ( customQueryHql != null && !customQueryHql.isEmpty() ) {
-			// TODO should I worry about the Lucene AddWork? If this is a
-			// restart, will it create duplicate index for the same entity,
-			// since there's no purge?
-			scroll = buildScrollUsingHQL( ss, customQueryHql );
-			partitionData = new PartitionContextData( partitionId, entityName );
-		}
-		// Criteria approach
-		else {
-			scroll = buildScrollUsingCriteria( ss, bound, checkpointId, jobData );
-			if ( checkpointId == null ) {
+		PartitionContextData partitionData;
+		switch ( PersistenceUtil.getIndexScope( customQueryHql, jobData.getCustomQueryCriteria() ) ) {
+			case HQL:
+				scroll = buildScrollUsingHQL( ss, customQueryHql );
 				partitionData = new PartitionContextData( partitionId, entityName );
-			}
-			else {
-				partitionData = (PartitionContextData) stepContext.getPersistentUserData();
-			}
+				break;
+
+			case CRITERIA:
+			case FULL_ENTITY:
+				scroll = buildScrollUsingCriteria( ss, bound, checkpointId, jobData );
+				if ( checkpointId == null ) {
+					partitionData = new PartitionContextData( partitionId, entityName );
+				}
+				else {
+					partitionData = (PartitionContextData) stepContext.getPersistentUserData();
+				}
+				break;
+
+			default:
+				// This should never happen.
+				throw new IllegalStateException( "Unknown value from enum: " + IndexScope.class );
 		}
-
 		stepContext.setTransientUserData( partitionData );
 	}
 

jsr352/core/src/main/java/org/hibernate/search/jsr352/massindexing/impl/steps/lucene/IndexScope.java

@@ -0,0 +1,29 @@
+/*
+ * Hibernate Search, full-text search for your domain model
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.search.jsr352.massindexing.impl.steps.lucene;
+
+import org.hibernate.Criteria;
+
+/**
+ * The index scope of a given entity type.
+ *
+ * @author Mincong Huang
+ */
+public enum IndexScope {
+	/**
+	 * Index entities restricted by the HQL / JPQL given by user.
+	 */
+	HQL,
+	/**
+	 * Index entities restricted the {@link Criteria} given by user.
+	 */
+	CRITERIA,
+	/**
+	 * Index all the entities found.
+	 */
+	FULL_ENTITY
+}

jsr352/core/src/main/java/org/hibernate/search/jsr352/massindexing/impl/steps/lucene/PartitionMapper.java

@@ -65,10 +65,6 @@ public class PartitionMapper implements javax.batch.api.partition.PartitionMappe
 
 	private static final Log log = LoggerFactory.make( Log.class );
 
-	private enum Type {
-		HQL, CRITERIA, FULL_ENTITY
-	}
-
 	@Inject
 	private JobContext jobContext;
 
@@ -136,7 +132,7 @@ public PartitionPlan mapPartitions() throws Exception {
 			List<PartitionBound> partitionBounds = new ArrayList<>();
 			Class<?> entityType;
 
-			switch ( typeOfSelection( customQueryHql, jobData.getCustomQueryCriteria() ) ) {
+			switch ( PersistenceUtil.getIndexScope( customQueryHql, jobData.getCustomQueryCriteria() ) ) {
 				case HQL:
 					entityType = entityTypes.get( 0 );
 					partitionBounds.add( new PartitionBound( entityType, null, null ) );
@@ -206,18 +202,6 @@ public PartitionPlan mapPartitions() throws Exception {
 		}
 	}
 
-	private Type typeOfSelection(String hql, Set<Criterion> criterions) {
-		if ( hql != null && !hql.isEmpty() ) {
-			return Type.HQL;
-		}
-		else if ( criterions != null && criterions.size() > 0 ) {
-			return Type.CRITERIA;
-		}
-		else {
-			return Type.FULL_ENTITY;
-		}
-	}
-
 	private List<PartitionBound> buildPartitionUnitsFrom(ScrollableResults scroll, Class<?> clazz) {
 		List<PartitionBound> partitionUnits = new ArrayList<>();
 		int rowsPerPartition = SerializationUtil.parseIntegerParameter( ROWS_PER_PARTITION, serializedRowsPerPartition );

jsr352/core/src/main/java/org/hibernate/search/jsr352/massindexing/impl/util/PersistenceUtil.java

@@ -6,11 +6,14 @@
  */
 package org.hibernate.search.jsr352.massindexing.impl.util;
 
+import java.util.Set;
 import javax.persistence.EntityManagerFactory;
 
 import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.hibernate.StatelessSession;
+import org.hibernate.criterion.Criterion;
+import org.hibernate.search.jsr352.massindexing.impl.steps.lucene.IndexScope;
 import org.hibernate.search.util.StringHelper;
 
 /**
@@ -71,4 +74,21 @@ public static StatelessSession openStatelessSession(EntityManagerFactory entityM
 		return statelessSession;
 	}
 
+	/**
+	 * Determines the index scope using the input parameters.
+	 *
+	 * @see IndexScope
+	 */
+	public static IndexScope getIndexScope(String hql, Set<Criterion> criterionSet) {
+		if ( StringHelper.isNotEmpty( hql ) ) {
+			return IndexScope.HQL;
+		}
+		else if ( criterionSet != null && criterionSet.size() > 0 ) {
+			return IndexScope.CRITERIA;
+		}
+		else {
+			return IndexScope.FULL_ENTITY;
+		}
+	}
+
 }