org.eclipse.mdm.api.odsadapter/src/main/java/org/eclipse/mdm/api/odsadapter/query/ODSQuery.java - mdmbl/org.eclipse.mdm - Git at Google

 /********************************************************************************
  * Copyright (c) 2015-2019 Contributors to the Eclipse Foundation
  *
  * See the NOTICE file(s) distributed with this work for additional
  * information regarding copyright ownership.
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License v. 2.0 which is available at
  * http://www.eclipse.org/legal/epl-2.0.
  *
  * SPDX-License-Identifier: EPL-2.0
  *
  ********************************************************************************/

 package org.eclipse.mdm.api.odsadapter.query;

 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.NoSuchElementException;
 import java.util.Optional;
 import java.util.Set;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;

 import org.asam.ods.AIDName;
 import org.asam.ods.AIDNameUnitId;
 import org.asam.ods.AoException;
 import org.asam.ods.ApplElemAccess;
 import org.asam.ods.ElemResultSetExt;
 import org.asam.ods.JoinDef;
 import org.asam.ods.NameValueSeqUnitId;
 import org.asam.ods.QueryStructureExt;
 import org.asam.ods.ResultSetExt;
 import org.asam.ods.SelAIDNameUnitId;
 import org.asam.ods.SelItem;
 import org.asam.ods.SelOrder;
 import org.asam.ods.SelValueExt;
 import org.asam.ods.T_LONGLONG;
 import org.eclipse.mdm.api.base.adapter.Attribute;
 import org.eclipse.mdm.api.base.adapter.EntityType;
 import org.eclipse.mdm.api.base.adapter.Relation;
 import org.eclipse.mdm.api.base.model.Value;
 import org.eclipse.mdm.api.base.query.Aggregation;
 import org.eclipse.mdm.api.base.query.Condition;
 import org.eclipse.mdm.api.base.query.DataAccessException;
 import org.eclipse.mdm.api.base.query.Filter;
 import org.eclipse.mdm.api.base.query.FilterItem;
 import org.eclipse.mdm.api.base.query.JoinType;
 import org.eclipse.mdm.api.base.query.Query;
 import org.eclipse.mdm.api.base.query.Record;
 import org.eclipse.mdm.api.base.query.Result;
 import org.eclipse.mdm.api.odsadapter.utils.ODSConverter;
 import org.eclipse.mdm.api.odsadapter.utils.ODSUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;

 import com.google.common.base.Strings;

 /**
  * ODS implementation of the {@link Query} interface.
  *
  * @since 1.0.0
  * @author Viktor Stoehr, Gigatronik Ingolstadt GmbH
  */
 public class ODSQuery implements Query {

 	// ======================================================================
 	// Class variables
 	// ======================================================================

 	private static final Logger LOGGER = LoggerFactory.getLogger(ODSQuery.class);

 	private static final String GROUP_NAME = "name";
 	private static final String GROUP_AGGRFUNC = "aggrfunc";
 	private static final Pattern AGGREGATION_NAME_PATTERN = Pattern
 			.compile("(?<" + GROUP_AGGRFUNC + ">\\S+)\\((?<" + GROUP_NAME + ">\\S+)\\)");

 	// ======================================================================
 	// Instance variables
 	// ======================================================================

 	private final Map<String, EntityType> entityTypesByID = new HashMap<>();
 	private final Set<EntityType> queriedEntityTypes = new HashSet<>();
 	private final List<SelAIDNameUnitId> anuSeq = new ArrayList<>();
 	private final List<JoinDef> joinSeq = new ArrayList<>();
 	private final List<AIDName> groupBy = new ArrayList<>();
 	private final List<SelOrder> orderBy = new ArrayList<>();

 	private final ApplElemAccess applElemAccess;

 	private int limit;

 	// ======================================================================
 	// Constructors
 	// ======================================================================

 	/**
 	 * Constructor.
 	 *
 	 * @param applElemAccess Used to execute the query.
 	 */
 	ODSQuery(ApplElemAccess applElemAccess) {
 		this.applElemAccess = applElemAccess;
 		limit = 0;
 	}

 	// ======================================================================
 	// Public methods
 	// ======================================================================

 	/**
 	 * {@inheritDoc}
 	 */
 	@Override
 	public boolean isQueried(EntityType entityType) {
 		return queriedEntityTypes.contains(entityType);
 	}

 	/**
 	 * {@inheritDoc}
 	 */
 	@Override
 	public Query limit(int limit) {
 		this.limit = limit;
 		return this;
 	}

 	/**
 	 * {@inheritDoc}
 	 */
 	@Override
 	public Query select(Attribute attribute, Aggregation aggregation) {
 		EntityType entityType = attribute.getEntityType();
 		entityTypesByID.put(Long.toString(ODSConverter.fromODSLong(((ODSEntityType) entityType).getODSID())),
 				entityType);
 		queriedEntityTypes.add(entityType);
 		anuSeq.add(createSelect(attribute, aggregation));
 		return this;
 	}

 	/**
 	 * {@inheritDoc}
 	 */
 	@Override
 	public Query join(Relation relation, JoinType join) {
 		queriedEntityTypes.add(relation.getSource());
 		queriedEntityTypes.add(relation.getTarget());
 		joinSeq.add(createJoin(relation, join));
 		return this;
 	}

 	/**
 	 * {@inheritDoc}
 	 */
 	@Override
 	public Query group(List<Attribute> attributes) {
 		for (Attribute attribute : attributes) {
 			group(attribute);
 		}
 		return this;
 	}

 	/**
 	 * {@inheritDoc}
 	 */
 	@Override
 	public Query group(Attribute attribute) {
 		groupBy.add(createAIDName(attribute));
 		return this;
 	}

 	/**
 	 * {@inheritDoc}
 	 */
 	@Override
 	public Query order(Attribute attribute, boolean ascending) {
 		orderBy.add(createOrderBy(attribute, ascending));
 		return this;
 	}

 	/**
 	 * {@inheritDoc}
 	 */
 	@Override
 	public Optional<Result> fetchSingleton(Filter filter) throws DataAccessException {
 		List<Result> results = fetch(filter);
 		if (results.isEmpty()) {
 			return Optional.empty();
 		} else if (results.size() > 1) {
 			throw new DataAccessException("Multiple results found after executing the singleton query!");
 		}

 		return Optional.of(results.get(0));
 	}

 	/**
 	 * {@inheritDoc}
 	 */
 	@Override
 	public List<Result> fetch(Filter filter) throws DataAccessException {
 		try {

 			List<SelItem> condSeq = new ArrayList<>();
 			int condCount = 0;
 			for (FilterItem conditionItem : filter) {
 				SelItem selItem = new SelItem();
 				if (conditionItem.isCondition()) {
 					selItem.value(createCondition(conditionItem.getCondition()));
 				} else if (conditionItem.isBracketOperator()) {
 					selItem._operator(ODSUtils.BRACKETOPERATORS.get(conditionItem.getBracketOperator()));
 				} else if (conditionItem.isBooleanOperator()) {
 					selItem._operator(ODSUtils.OPERATORS.get(conditionItem.getBooleanOperator()));
 					condCount++;
 				} else {
 					throw new IllegalArgumentException("Passed filter item is neither an operator nor a condition.");
 				}

 				condSeq.add(selItem);
 			}

 			QueryStructureExt qse = new QueryStructureExt();
 			qse.anuSeq = anuSeq.toArray(new SelAIDNameUnitId[anuSeq.size()]);
 			qse.condSeq = condSeq.toArray(new SelItem[condSeq.size()]);
 			qse.groupBy = groupBy.toArray(new AIDName[groupBy.size()]);
 			qse.joinSeq = joinSeq.toArray(new JoinDef[joinSeq.size()]);
 			qse.orderBy = orderBy.toArray(new SelOrder[orderBy.size()]);

 			List<Result> results = new ArrayList<>();
 			long start = System.currentTimeMillis();
 			for (Result result : new ResultFactory(entityTypesByID, applElemAccess.getInstancesExt(qse, limit)[0])) {
 				results.add(result);
 			}
 			long stop = System.currentTimeMillis();

 			LOGGER.debug("Query executed in {} ms and retrieved {} result rows ({} selections, {} conditions, "
 					+ "{} joins).", stop - start, results.size(), anuSeq.size(), condCount, joinSeq.size());
 			return results;
 		} catch (AoException aoe) {
 			throw new DataAccessException(aoe.reason, aoe);
 		}
 	}

 	// ======================================================================
 	// Private methods
 	// ======================================================================

 	/**
 	 * Converts given {@link Attribute} and {@link Aggregation} to an ODS
 	 * {@link SelAIDNameUnitId}.
 	 *
 	 * @param attribute   The {@code Attribute}.
 	 * @param aggregation The {@code Aggregation}.
 	 * @return The corresponding {@code SelAIDNameUnitId} is returned.
 	 */
 	private SelAIDNameUnitId createSelect(Attribute attribute, Aggregation aggregation) {
 		SelAIDNameUnitId sanu = new SelAIDNameUnitId();

 		sanu.aggregate = ODSUtils.AGGREGATIONS.get(aggregation);
 		sanu.attr = createAIDName(attribute);
 		sanu.unitId = new T_LONGLONG();

 		return sanu;
 	}

 	/**
 	 * Converts given {@link Condition} to an ODS {@link SelValueExt}.
 	 *
 	 * @param condition The {@code Condition}.
 	 * @return The corresponding {@code SelValueExt} is returned.
 	 * @throws DataAccessException Thrown in case of errors.
 	 */
 	private SelValueExt createCondition(Condition condition) throws DataAccessException {
 		SelValueExt sve = new SelValueExt();

 		sve.oper = ODSUtils.OPERATIONS.get(condition.getComparisonOperator());
 		sve.attr = new AIDNameUnitId();
 		sve.attr.unitId = new T_LONGLONG();
 		sve.attr.attr = createAIDName(condition.getAttribute());
 		sve.value = ODSConverter.toODSValue(condition.getAttribute(), condition.getValue());

 		return sve;
 	}

 	/**
 	 * Converts given {@link Relation} and {@link JoinType} to an ODS
 	 * {@link JoinDef}.
 	 *
 	 * @param relation The {@code Relation}.
 	 * @param join     The {@code JoinType}.
 	 * @return The corresponding {@code JoinDef} is returned.
 	 */
 	private JoinDef createJoin(Relation relation, JoinType join) {
 		JoinDef joinDef = new JoinDef();

 		joinDef.fromAID = ((ODSEntityType) relation.getSource()).getODSID();
 		joinDef.toAID = ((ODSEntityType) relation.getTarget()).getODSID();
 		joinDef.refName = relation.getName();
 		joinDef.joiningType = ODSUtils.JOINS.get(join);

 		return joinDef;
 	}

 	/**
 	 * Converts given {@link Attribute} and sort order flag to an ODS
 	 * {@link SelOrder}.
 	 *
 	 * @param attribute The {@code Attribute}.
 	 * @param ascending The sort order.
 	 * @return The corresponding {@code SelOrder} is returned.
 	 */
 	private SelOrder createOrderBy(Attribute attribute, boolean ascending) {
 		SelOrder selOrder = new SelOrder();

 		selOrder.attr = createAIDName(attribute);
 		selOrder.ascending = ascending;

 		return selOrder;
 	}

 	/**
 	 * Converts given {@link Attribute} to an ODS {@link AIDName}.
 	 *
 	 * @param attribute The {@code Attribute}.
 	 * @return The corresponding {@code AIDName} is returned.
 	 */
 	private AIDName createAIDName(Attribute attribute) {
 		AIDName aidName = new AIDName();

 		aidName.aid = ((ODSEntityType) attribute.getEntityType()).getODSID();
 		aidName.aaName = attribute.getName();

 		return aidName;
 	}

 	private static Aggregation getAggregation(String odsAggrFunc) {
 		switch (Strings.nullToEmpty(odsAggrFunc).trim().toUpperCase()) {
 		case "COUNT":
 			return Aggregation.COUNT;
 		case "DCOUNT":
 			return Aggregation.DISTINCT_COUNT;
 		case "MIN":
 			return Aggregation.MINIMUM;
 		case "MAX":
 			return Aggregation.MAXIMUM;
 		case "AVG":
 			return Aggregation.AVERAGE;
 		case "STDDEV":
 			return Aggregation.DEVIATION;
 		case "SUM":
 			return Aggregation.SUM;
 		case "DISTINCT":
 			return Aggregation.DISTINCT;
 		default:
 			throw new IllegalArgumentException(
 					"Unsupported aggregate function '" + Strings.nullToEmpty(odsAggrFunc).trim().toUpperCase() + "'!");
 		}

 	}

 	// ======================================================================
 	// Inner classes
 	// ======================================================================

 	/**
 	 * Traverses the ODS {@link ResultSetExt} and creates a {@link Result} for each
 	 * row.
 	 */
 	private static final class ResultFactory implements Iterable<Result>, Iterator<Result> {

 		// ======================================================================
 		// Instance variables
 		// ======================================================================

 		private final List<RecordFactory> recordFactories = new ArrayList<>();
 		private final int length;
 		private int index;

 		// ======================================================================
 		// Constructors
 		// ======================================================================

 		/**
 		 * Constructor.
 		 *
 		 * @param entityTypes  Used to access {@link EntityType} by its ODS ID.
 		 * @param resultSetExt The ODS values sequence containers.
 		 * @throws DataAccessException Thrown on conversion errors.
 		 */
 		public ResultFactory(Map<String, EntityType> entityTypes, ResultSetExt resultSetExt)
 				throws DataAccessException {
 			for (ElemResultSetExt elemResultSetExt : resultSetExt.firstElems) {
 				EntityType entityType = entityTypes.get(Long.toString(ODSConverter.fromODSLong(elemResultSetExt.aid)));
 				recordFactories.add(new RecordFactory(entityType, elemResultSetExt.values));
 			}

 			length = recordFactories.isEmpty() ? 0 : recordFactories.get(0).getLength();
 		}

 		// ======================================================================
 		// Public methods
 		// ======================================================================

 		/**
 		 * {@inheritDoc}
 		 */
 		@Override
 		public boolean hasNext() {
 			return index < length;
 		}

 		/**
 		 * {@inheritDoc}
 		 */
 		@Override
 		public Result next() {
 			if (!hasNext()) {
 				throw new NoSuchElementException("No such element available.");
 			}
 			Result result = new Result();

 			for (RecordFactory recordFactory : recordFactories) {
 				result.addRecord(recordFactory.createRecord(index));
 			}

 			index++;
 			return result;
 		}

 		/**
 		 * {@inheritDoc}
 		 */
 		@Override
 		public Iterator<Result> iterator() {
 			return this;
 		}

 	}

 	/**
 	 * Creates a {@link Record} for given index from the original ODS values
 	 * sequence for a given {@link EntityType}.
 	 */
 	private static final class RecordFactory {

 		// ======================================================================
 		// Instance variables
 		// ======================================================================

 		private final List<ValueFactory> valueFactories = new ArrayList<>();
 		private final EntityType entityType;

 		// ======================================================================
 		// Constructors
 		// ======================================================================

 		/**
 		 * Constructor.
 		 *
 		 * @param entityType The associated {@link EntityType}.
 		 * @param nvsuis     The ODS value sequence containers.
 		 * @throws DataAccessException Thrown on conversion errors.
 		 */
 		private RecordFactory(EntityType entityType, NameValueSeqUnitId[] nvsuis) throws DataAccessException {
 			this.entityType = entityType;
 			for (NameValueSeqUnitId nvsui : nvsuis) {
 				String attributeName = nvsui.valName;
 				Aggregation aggregation = Aggregation.NONE;
 				Matcher matcher = AGGREGATION_NAME_PATTERN.matcher(nvsui.valName);
 				if (matcher.matches()) {
 					attributeName = matcher.group(GROUP_NAME);
 					aggregation = ODSQuery.getAggregation(matcher.group(GROUP_AGGRFUNC));
 				}

 				valueFactories.add(new ValueFactory(entityType.getAttribute(attributeName), aggregation, nvsui));
 			}
 		}

 		// ======================================================================
 		// Private methods
 		// ======================================================================

 		private int getLength() {
 			return valueFactories.isEmpty() ? 0 : valueFactories.get(0).getLength();
 		}

 		private Record createRecord(int index) {
 			Record record = new Record(entityType);
 			for (ValueFactory valueFactory : valueFactories) {
 				record.addValue(valueFactory.createValue(index));
 			}

 			return record;
 		}

 	}

 	/**
 	 * Creates a {@link Value} container for given index from the original ODS value
 	 * sequence for a given {@link Attribute}.
 	 */
 	private static final class ValueFactory {

 		// ======================================================================
 		// Instance variables
 		// ======================================================================

 		private final List<Value> values;
 		private final String unit;
 		private final int length;

 		// ======================================================================
 		// Constructors
 		// ======================================================================

 		/**
 		 * Constructor.
 		 *
 		 * @param attribute The associated {@link Attribute}.
 		 * @param nvsui     The ODS value sequence container.
 		 * @throws DataAccessException Thrown on conversion errors.
 		 */
 		private ValueFactory(Attribute attribute, Aggregation aggregation, NameValueSeqUnitId nvsui)
 				throws DataAccessException {
 			length = nvsui.value.flag.length;
 			unit = attribute.getUnit();
 			values = ODSConverter.fromODSValueSeq(attribute, aggregation, unit, nvsui.value);
 		}

 		// ======================================================================
 		// Private methods
 		// ======================================================================

 		/**
 		 * Returns the length of the sequence.
 		 *
 		 * @return Length of the sequence is returned.
 		 */
 		private int getLength() {
 			return length;
 		}

 		/**
 		 * Returns the {@link Value} for given index.
 		 *
 		 * @param index Index within the sequence.
 		 * @return The corresponding {@code Value} is returned.
 		 */
 		private Value createValue(int index) {
 			return values.get(index);
 		}

 	}

 }
	/********************************************************************************
	* Copyright (c) 2015-2019 Contributors to the Eclipse Foundation
	*
	* See the NOTICE file(s) distributed with this work for additional
	* information regarding copyright ownership.
	*
	* This program and the accompanying materials are made available under the
	* terms of the Eclipse Public License v. 2.0 which is available at
	* http://www.eclipse.org/legal/epl-2.0.
	*
	* SPDX-License-Identifier: EPL-2.0
	*
	********************************************************************************/

	package org.eclipse.mdm.api.odsadapter.query;

	import java.util.ArrayList;
	import java.util.HashMap;
	import java.util.HashSet;
	import java.util.Iterator;
	import java.util.List;
	import java.util.Map;
	import java.util.NoSuchElementException;
	import java.util.Optional;
	import java.util.Set;
	import java.util.regex.Matcher;
	import java.util.regex.Pattern;

	import org.asam.ods.AIDName;
	import org.asam.ods.AIDNameUnitId;
	import org.asam.ods.AoException;
	import org.asam.ods.ApplElemAccess;
	import org.asam.ods.ElemResultSetExt;
	import org.asam.ods.JoinDef;
	import org.asam.ods.NameValueSeqUnitId;
	import org.asam.ods.QueryStructureExt;
	import org.asam.ods.ResultSetExt;
	import org.asam.ods.SelAIDNameUnitId;
	import org.asam.ods.SelItem;
	import org.asam.ods.SelOrder;
	import org.asam.ods.SelValueExt;
	import org.asam.ods.T_LONGLONG;
	import org.eclipse.mdm.api.base.adapter.Attribute;
	import org.eclipse.mdm.api.base.adapter.EntityType;
	import org.eclipse.mdm.api.base.adapter.Relation;
	import org.eclipse.mdm.api.base.model.Value;
	import org.eclipse.mdm.api.base.query.Aggregation;
	import org.eclipse.mdm.api.base.query.Condition;
	import org.eclipse.mdm.api.base.query.DataAccessException;
	import org.eclipse.mdm.api.base.query.Filter;
	import org.eclipse.mdm.api.base.query.FilterItem;
	import org.eclipse.mdm.api.base.query.JoinType;
	import org.eclipse.mdm.api.base.query.Query;
	import org.eclipse.mdm.api.base.query.Record;
	import org.eclipse.mdm.api.base.query.Result;
	import org.eclipse.mdm.api.odsadapter.utils.ODSConverter;
	import org.eclipse.mdm.api.odsadapter.utils.ODSUtils;
	import org.slf4j.Logger;
	import org.slf4j.LoggerFactory;

	import com.google.common.base.Strings;

	/**
	* ODS implementation of the {@link Query} interface.
	*
	* @since 1.0.0
	* @author Viktor Stoehr, Gigatronik Ingolstadt GmbH
	*/
	public class ODSQuery implements Query {

	// ======================================================================
	// Class variables
	// ======================================================================

	private static final Logger LOGGER = LoggerFactory.getLogger(ODSQuery.class);

	private static final String GROUP_NAME = "name";
	private static final String GROUP_AGGRFUNC = "aggrfunc";
	private static final Pattern AGGREGATION_NAME_PATTERN = Pattern
	.compile("(?<" + GROUP_AGGRFUNC + ">\\S+)\\((?<" + GROUP_NAME + ">\\S+)\\)");

	// ======================================================================
	// Instance variables
	// ======================================================================

	private final Map<String, EntityType> entityTypesByID = new HashMap<>();
	private final Set<EntityType> queriedEntityTypes = new HashSet<>();
	private final List<SelAIDNameUnitId> anuSeq = new ArrayList<>();
	private final List<JoinDef> joinSeq = new ArrayList<>();
	private final List<AIDName> groupBy = new ArrayList<>();
	private final List<SelOrder> orderBy = new ArrayList<>();

	private final ApplElemAccess applElemAccess;

	private int limit;

	// ======================================================================
	// Constructors
	// ======================================================================

	/**
	* Constructor.
	*
	* @param applElemAccess Used to execute the query.
	*/
	ODSQuery(ApplElemAccess applElemAccess) {
	this.applElemAccess = applElemAccess;
	limit = 0;
	}

	// ======================================================================
	// Public methods
	// ======================================================================

	/**
	* {@inheritDoc}
	*/
	@Override
	public boolean isQueried(EntityType entityType) {
	return queriedEntityTypes.contains(entityType);
	}

	/**
	* {@inheritDoc}
	*/
	@Override
	public Query limit(int limit) {
	this.limit = limit;
	return this;
	}

	/**
	* {@inheritDoc}
	*/
	@Override
	public Query select(Attribute attribute, Aggregation aggregation) {
	EntityType entityType = attribute.getEntityType();
	entityTypesByID.put(Long.toString(ODSConverter.fromODSLong(((ODSEntityType) entityType).getODSID())),
	entityType);
	queriedEntityTypes.add(entityType);
	anuSeq.add(createSelect(attribute, aggregation));
	return this;
	}

	/**
	* {@inheritDoc}
	*/
	@Override
	public Query join(Relation relation, JoinType join) {
	queriedEntityTypes.add(relation.getSource());
	queriedEntityTypes.add(relation.getTarget());
	joinSeq.add(createJoin(relation, join));
	return this;
	}

	/**
	* {@inheritDoc}
	*/
	@Override
	public Query group(List<Attribute> attributes) {
	for (Attribute attribute : attributes) {
	group(attribute);
	}
	return this;
	}

	/**
	* {@inheritDoc}
	*/
	@Override
	public Query group(Attribute attribute) {
	groupBy.add(createAIDName(attribute));
	return this;
	}

	/**
	* {@inheritDoc}
	*/
	@Override
	public Query order(Attribute attribute, boolean ascending) {
	orderBy.add(createOrderBy(attribute, ascending));
	return this;
	}

	/**
	* {@inheritDoc}
	*/
	@Override
	public Optional<Result> fetchSingleton(Filter filter) throws DataAccessException {
	List<Result> results = fetch(filter);
	if (results.isEmpty()) {
	return Optional.empty();
	} else if (results.size() > 1) {
	throw new DataAccessException("Multiple results found after executing the singleton query!");
	}

	return Optional.of(results.get(0));
	}

	/**
	* {@inheritDoc}
	*/
	@Override
	public List<Result> fetch(Filter filter) throws DataAccessException {
	try {

	List<SelItem> condSeq = new ArrayList<>();
	int condCount = 0;
	for (FilterItem conditionItem : filter) {
	SelItem selItem = new SelItem();
	if (conditionItem.isCondition()) {
	selItem.value(createCondition(conditionItem.getCondition()));
	} else if (conditionItem.isBracketOperator()) {
	selItem._operator(ODSUtils.BRACKETOPERATORS.get(conditionItem.getBracketOperator()));
	} else if (conditionItem.isBooleanOperator()) {
	selItem._operator(ODSUtils.OPERATORS.get(conditionItem.getBooleanOperator()));
	condCount++;
	} else {
	throw new IllegalArgumentException("Passed filter item is neither an operator nor a condition.");
	}

	condSeq.add(selItem);
	}

	QueryStructureExt qse = new QueryStructureExt();
	qse.anuSeq = anuSeq.toArray(new SelAIDNameUnitId[anuSeq.size()]);
	qse.condSeq = condSeq.toArray(new SelItem[condSeq.size()]);
	qse.groupBy = groupBy.toArray(new AIDName[groupBy.size()]);
	qse.joinSeq = joinSeq.toArray(new JoinDef[joinSeq.size()]);
	qse.orderBy = orderBy.toArray(new SelOrder[orderBy.size()]);

	List<Result> results = new ArrayList<>();
	long start = System.currentTimeMillis();
	for (Result result : new ResultFactory(entityTypesByID, applElemAccess.getInstancesExt(qse, limit)[0])) {
	results.add(result);
	}
	long stop = System.currentTimeMillis();

	LOGGER.debug("Query executed in {} ms and retrieved {} result rows ({} selections, {} conditions, "
	+ "{} joins).", stop - start, results.size(), anuSeq.size(), condCount, joinSeq.size());
	return results;
	} catch (AoException aoe) {
	throw new DataAccessException(aoe.reason, aoe);
	}
	}

	// ======================================================================
	// Private methods
	// ======================================================================

	/**
	* Converts given {@link Attribute} and {@link Aggregation} to an ODS
	* {@link SelAIDNameUnitId}.
	*
	* @param attribute The {@code Attribute}.
	* @param aggregation The {@code Aggregation}.
	* @return The corresponding {@code SelAIDNameUnitId} is returned.
	*/
	private SelAIDNameUnitId createSelect(Attribute attribute, Aggregation aggregation) {
	SelAIDNameUnitId sanu = new SelAIDNameUnitId();

	sanu.aggregate = ODSUtils.AGGREGATIONS.get(aggregation);
	sanu.attr = createAIDName(attribute);
	sanu.unitId = new T_LONGLONG();

	return sanu;
	}

	/**
	* Converts given {@link Condition} to an ODS {@link SelValueExt}.
	*
	* @param condition The {@code Condition}.
	* @return The corresponding {@code SelValueExt} is returned.
	* @throws DataAccessException Thrown in case of errors.
	*/
	private SelValueExt createCondition(Condition condition) throws DataAccessException {
	SelValueExt sve = new SelValueExt();

	sve.oper = ODSUtils.OPERATIONS.get(condition.getComparisonOperator());
	sve.attr = new AIDNameUnitId();
	sve.attr.unitId = new T_LONGLONG();
	sve.attr.attr = createAIDName(condition.getAttribute());
	sve.value = ODSConverter.toODSValue(condition.getAttribute(), condition.getValue());

	return sve;
	}

	/**
	* Converts given {@link Relation} and {@link JoinType} to an ODS
	* {@link JoinDef}.
	*
	* @param relation The {@code Relation}.
	* @param join The {@code JoinType}.
	* @return The corresponding {@code JoinDef} is returned.
	*/
	private JoinDef createJoin(Relation relation, JoinType join) {
	JoinDef joinDef = new JoinDef();

	joinDef.fromAID = ((ODSEntityType) relation.getSource()).getODSID();
	joinDef.toAID = ((ODSEntityType) relation.getTarget()).getODSID();
	joinDef.refName = relation.getName();
	joinDef.joiningType = ODSUtils.JOINS.get(join);

	return joinDef;
	}

	/**
	* Converts given {@link Attribute} and sort order flag to an ODS
	* {@link SelOrder}.
	*
	* @param attribute The {@code Attribute}.
	* @param ascending The sort order.
	* @return The corresponding {@code SelOrder} is returned.
	*/
	private SelOrder createOrderBy(Attribute attribute, boolean ascending) {
	SelOrder selOrder = new SelOrder();

	selOrder.attr = createAIDName(attribute);
	selOrder.ascending = ascending;

	return selOrder;
	}

	/**
	* Converts given {@link Attribute} to an ODS {@link AIDName}.
	*
	* @param attribute The {@code Attribute}.
	* @return The corresponding {@code AIDName} is returned.
	*/
	private AIDName createAIDName(Attribute attribute) {
	AIDName aidName = new AIDName();

	aidName.aid = ((ODSEntityType) attribute.getEntityType()).getODSID();
	aidName.aaName = attribute.getName();

	return aidName;
	}

	private static Aggregation getAggregation(String odsAggrFunc) {
	switch (Strings.nullToEmpty(odsAggrFunc).trim().toUpperCase()) {
	case "COUNT":
	return Aggregation.COUNT;
	case "DCOUNT":
	return Aggregation.DISTINCT_COUNT;
	case "MIN":
	return Aggregation.MINIMUM;
	case "MAX":
	return Aggregation.MAXIMUM;
	case "AVG":
	return Aggregation.AVERAGE;
	case "STDDEV":
	return Aggregation.DEVIATION;
	case "SUM":
	return Aggregation.SUM;
	case "DISTINCT":
	return Aggregation.DISTINCT;
	default:
	throw new IllegalArgumentException(
	"Unsupported aggregate function '" + Strings.nullToEmpty(odsAggrFunc).trim().toUpperCase() + "'!");
	}

	}

	// ======================================================================
	// Inner classes
	// ======================================================================

	/**
	* Traverses the ODS {@link ResultSetExt} and creates a {@link Result} for each
	* row.
	*/
	private static final class ResultFactory implements Iterable<Result>, Iterator<Result> {

	// ======================================================================
	// Instance variables
	// ======================================================================

	private final List<RecordFactory> recordFactories = new ArrayList<>();
	private final int length;
	private int index;

	// ======================================================================
	// Constructors
	// ======================================================================

	/**
	* Constructor.
	*
	* @param entityTypes Used to access {@link EntityType} by its ODS ID.
	* @param resultSetExt The ODS values sequence containers.
	* @throws DataAccessException Thrown on conversion errors.
	*/
	public ResultFactory(Map<String, EntityType> entityTypes, ResultSetExt resultSetExt)
	throws DataAccessException {
	for (ElemResultSetExt elemResultSetExt : resultSetExt.firstElems) {
	EntityType entityType = entityTypes.get(Long.toString(ODSConverter.fromODSLong(elemResultSetExt.aid)));
	recordFactories.add(new RecordFactory(entityType, elemResultSetExt.values));
	}

	length = recordFactories.isEmpty() ? 0 : recordFactories.get(0).getLength();
	}

	// ======================================================================
	// Public methods
	// ======================================================================

	/**
	* {@inheritDoc}
	*/
	@Override
	public boolean hasNext() {
	return index < length;
	}

	/**
	* {@inheritDoc}
	*/
	@Override
	public Result next() {
	if (!hasNext()) {
	throw new NoSuchElementException("No such element available.");
	}
	Result result = new Result();

	for (RecordFactory recordFactory : recordFactories) {
	result.addRecord(recordFactory.createRecord(index));
	}

	index++;
	return result;
	}

	/**
	* {@inheritDoc}
	*/
	@Override
	public Iterator<Result> iterator() {
	return this;
	}

	}

	/**
	* Creates a {@link Record} for given index from the original ODS values
	* sequence for a given {@link EntityType}.
	*/
	private static final class RecordFactory {

	// ======================================================================
	// Instance variables
	// ======================================================================

	private final List<ValueFactory> valueFactories = new ArrayList<>();
	private final EntityType entityType;

	// ======================================================================
	// Constructors
	// ======================================================================

	/**
	* Constructor.
	*
	* @param entityType The associated {@link EntityType}.
	* @param nvsuis The ODS value sequence containers.
	* @throws DataAccessException Thrown on conversion errors.
	*/
	private RecordFactory(EntityType entityType, NameValueSeqUnitId[] nvsuis) throws DataAccessException {
	this.entityType = entityType;
	for (NameValueSeqUnitId nvsui : nvsuis) {
	String attributeName = nvsui.valName;
	Aggregation aggregation = Aggregation.NONE;
	Matcher matcher = AGGREGATION_NAME_PATTERN.matcher(nvsui.valName);
	if (matcher.matches()) {
	attributeName = matcher.group(GROUP_NAME);
	aggregation = ODSQuery.getAggregation(matcher.group(GROUP_AGGRFUNC));
	}

	valueFactories.add(new ValueFactory(entityType.getAttribute(attributeName), aggregation, nvsui));
	}
	}

	// ======================================================================
	// Private methods
	// ======================================================================

	private int getLength() {
	return valueFactories.isEmpty() ? 0 : valueFactories.get(0).getLength();
	}

	private Record createRecord(int index) {
	Record record = new Record(entityType);
	for (ValueFactory valueFactory : valueFactories) {
	record.addValue(valueFactory.createValue(index));
	}

	return record;
	}

	}

	/**
	* Creates a {@link Value} container for given index from the original ODS value
	* sequence for a given {@link Attribute}.
	*/
	private static final class ValueFactory {

	// ======================================================================
	// Instance variables
	// ======================================================================

	private final List<Value> values;
	private final String unit;
	private final int length;

	// ======================================================================
	// Constructors
	// ======================================================================

	/**
	* Constructor.
	*
	* @param attribute The associated {@link Attribute}.
	* @param nvsui The ODS value sequence container.
	* @throws DataAccessException Thrown on conversion errors.
	*/
	private ValueFactory(Attribute attribute, Aggregation aggregation, NameValueSeqUnitId nvsui)
	throws DataAccessException {
	length = nvsui.value.flag.length;
	unit = attribute.getUnit();
	values = ODSConverter.fromODSValueSeq(attribute, aggregation, unit, nvsui.value);
	}

	// ======================================================================
	// Private methods
	// ======================================================================

	/**
	* Returns the length of the sequence.
	*
	* @return Length of the sequence is returned.
	*/
	private int getLength() {
	return length;
	}

	/**
	* Returns the {@link Value} for given index.
	*
	* @param index Index within the sequence.
	* @return The corresponding {@code Value} is returned.
	*/
	private Value createValue(int index) {
	return values.get(index);
	}

	}

	}