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ResultTransformer interface and implementation for grouping of projected rows
This commit is contained in:
Samppa Saarela
parent
d33e0729bb
commit
f35479759d
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package com.mysema.query;
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public interface ResultTransformer<T> {
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public T transform(Projectable projectable);
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}
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/*
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* Copyright (c) 2010 Mysema Ltd.
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* All rights reserved.
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*
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*/
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package com.mysema.query.support;
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import java.util.List;
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import javax.annotation.Nullable;
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import com.mysema.query.types.Expression;
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/**
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* An interface for grouped results. Group identifier is always the first element.
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*
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* @author sasa
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*/
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public interface Group {
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/**
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* Get an element of first row of this group by index
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*
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* @param <T>
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* @param index
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* @param type
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* @return
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*/
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@Nullable
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<T> T get(int index, Class<T> type);
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/**
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* Get an element of first row of this group by expr
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*
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* @param <T>
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* @param expr
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* @return
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*/
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@Nullable
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<T> T get(Expression<T> expr);
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/**
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* Get a list of elements (all rows) of this group by expression
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*
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* @param <T>
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* @param index
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* @param type
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* @return
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*/
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@Nullable
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<T> List<T> getList(int index, Class<T> type);
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/**
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* Get a list of elements (all rows) of this group by expression
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*
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* @param <T>
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* @param expr
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* @return
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*/
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@Nullable
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<T> List<T> getList(Expression<T> expr);
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int size();
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}
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/*
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* Copyright (c) 2010 Mysema Ltd.
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* All rights reserved.
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*
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*/
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package com.mysema.query.support;
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import java.util.ArrayList;
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import java.util.Collection;
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import java.util.LinkedHashMap;
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import java.util.List;
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import com.mysema.commons.lang.CloseableIterator;
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import com.mysema.query.Projectable;
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import com.mysema.query.ResultTransformer;
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import com.mysema.query.types.Expression;
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/**
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* Groups results by the first expression.
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* <ol>
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* <li>Order of groups by position of the first row of a group
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* <li>Rows belonging to a group may appear in any order
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* <li>Group of null is handled correctly
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* </ol>
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*
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* @author sasa
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*/
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public class GroupBy implements ResultTransformer<Collection<Group>> {
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private static final long serialVersionUID = 1L;
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private final Expression<?>[] expressions;
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public GroupBy(Expression<?> groupBy, Expression<?>... args) {
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expressions = new Expression<?>[args.length + 1];
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expressions[0] = groupBy;
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for (int i=0; i < args.length; i++) {
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expressions[i+1] = args[i];
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}
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}
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@Override
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public Collection<Group> transform(Projectable projectable) {
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final LinkedHashMap<Object, Group> groups = new LinkedHashMap<Object, Group>();
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CloseableIterator<Object[]> iter = projectable.iterate(expressions);
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try {
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while (iter.hasNext()) {
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Object[] row = iter.next();
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Object groupBy = row[0];
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// groups.values() should return Collection<GTuple> instead of Collection<? extends GTuple>
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GTupleImpl group = (GTupleImpl) groups.get(groupBy);
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if (group == null) {
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group = new GTupleImpl();
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groups.put(groupBy, group);
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}
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group.add(row);
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}
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} finally {
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iter.close();
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}
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return groups.values();
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}
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private int indexOf(Expression<?> expr) {
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for (int i=0; i < expressions.length; i++) {
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if (expressions[i].equals(expr)) {
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return i;
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}
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}
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return -1;
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}
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@SuppressWarnings("unchecked")
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private class GTupleImpl implements Group {
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private final List<Object[]> values = new ArrayList<Object[]>();
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@Override
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public <T> T get(int index, Class<T> type) {
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return (T) values.get(0)[index];
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}
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private void add(Object[] row) {
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this.values.add(row);
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}
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@Override
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public <T> T get(Expression<T> expr) {
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int index = indexOf(expr);
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return index != -1 ? (T) values.get(0)[index] : null;
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}
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@Override
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public <T> List<T> getList(int index, Class<T> type) {
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List<T> list = new ArrayList<T>(values.size());
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for (Object[] o : values) {
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list.add((T) o[index]);
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}
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return list;
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}
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@Override
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public <T> List<T> getList(Expression<T> expr) {
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int index = indexOf(expr);
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if (index < 0) {
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return null;
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} else {
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List<T> list = new ArrayList<T>(values.size());
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for (Object[] o : values) {
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list.add((T) o[index]);
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}
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return list;
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}
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}
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public int size() {
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return values.size();
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}
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}
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}
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@ -0,0 +1,151 @@
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/*
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* Copyright (c) 2010 Mysema Ltd.
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* All rights reserved.
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*
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*/
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package com.mysema.query.support;
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import java.util.Collections;
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import java.util.List;
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import java.util.Map;
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import com.mysema.commons.lang.CloseableIterator;
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import com.mysema.commons.lang.EmptyCloseableIterator;
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import com.mysema.query.Projectable;
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import com.mysema.query.SearchResults;
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import com.mysema.query.types.Expression;
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public class AbstractProjectable implements Projectable {
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@Override
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public long count() {
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return 0;
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}
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@Override
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public long countDistinct() {
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return 0;
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}
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@Override
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public boolean exists() {
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return 0 < count();
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}
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@Override
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public boolean notExists() {
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return !exists();
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}
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@Override
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public CloseableIterator<Object[]> iterate(Expression<?> first,
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Expression<?> second, Expression<?>... rest) {
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return null;
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}
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@Override
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public CloseableIterator<Object[]> iterate(Expression<?>[] args) {
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return new EmptyCloseableIterator<Object[]>();
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}
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@Override
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public <RT> CloseableIterator<RT> iterate(Expression<RT> projection) {
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return new EmptyCloseableIterator<RT>();
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}
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@Override
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public CloseableIterator<Object[]> iterateDistinct(Expression<?> first,
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Expression<?> second, Expression<?>... rest) {
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return new EmptyCloseableIterator<Object[]>();
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}
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@Override
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public CloseableIterator<Object[]> iterateDistinct(Expression<?>[] args) {
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return new EmptyCloseableIterator<Object[]>();
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}
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@Override
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public <RT> CloseableIterator<RT> iterateDistinct(Expression<RT> projection) {
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return new EmptyCloseableIterator<RT>();
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}
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@Override
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public List<Object[]> list(Expression<?> first, Expression<?> second,
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Expression<?>... rest) {
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return Collections.emptyList();
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}
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@Override
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public List<Object[]> list(Expression<?>[] args) {
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return Collections.emptyList();
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}
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@Override
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public <RT> List<RT> list(Expression<RT> projection) {
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return Collections.emptyList();
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}
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@Override
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public List<Object[]> listDistinct(Expression<?> first,
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Expression<?> second, Expression<?>... rest) {
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return Collections.emptyList();
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}
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@Override
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public List<Object[]> listDistinct(Expression<?>[] args) {
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return Collections.emptyList();
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}
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@Override
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public <RT> List<RT> listDistinct(Expression<RT> projection) {
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return Collections.emptyList();
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}
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@Override
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public <RT> SearchResults<RT> listResults(Expression<RT> projection) {
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return new SearchResults<RT>(Collections.<RT>emptyList(), null, null, 0l);
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}
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@Override
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public <RT> SearchResults<RT> listDistinctResults(Expression<RT> projection) {
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return new SearchResults<RT>(Collections.<RT>emptyList(), null, null, 0l);
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}
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@Override
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public <K, V> Map<K, V> map(Expression<K> key, Expression<V> value) {
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return Collections.emptyMap();
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}
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@Override
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public Object[] singleResult(Expression<?> first, Expression<?> second,
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Expression<?>... rest) {
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return new Object[0];
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}
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@Override
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public Object[] singleResult(Expression<?>[] args) {
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return null;
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}
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@Override
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public <RT> RT singleResult(Expression<RT> projection) {
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return null;
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}
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@Override
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public Object[] uniqueResult(Expression<?> first, Expression<?> second,
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Expression<?>... rest) {
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return null;
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}
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@Override
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public Object[] uniqueResult(Expression<?>[] args) {
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return null;
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}
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@Override
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public <RT> RT uniqueResult(Expression<RT> projection) {
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return null;
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}
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}
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@ -0,0 +1,104 @@
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package com.mysema.query.support;
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import static junit.framework.Assert.assertEquals;
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import java.util.Arrays;
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import java.util.Collection;
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import java.util.Iterator;
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import java.util.List;
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import org.junit.Test;
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import com.mysema.commons.lang.CloseableIterator;
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import com.mysema.commons.lang.IteratorAdapter;
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import com.mysema.query.types.Expression;
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import com.mysema.query.types.expr.NumberExpression;
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import com.mysema.query.types.expr.StringExpression;
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import com.mysema.query.types.path.NumberPath;
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import com.mysema.query.types.path.StringPath;
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public class GroupByTest {
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private final NumberExpression<Integer> postId = new NumberPath(Integer.class, null, "postId");
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private final StringExpression postName = new StringPath(null, "postName");
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private final NumberExpression<Integer> commentId = new NumberPath(Integer.class, null, "commentId");
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/**
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* <ol>
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* <li>Order of groups by first row of a group
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* <li>Rows belonging to a group may appear in any order
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* <li>Group of null is handled correctly
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* </ol>
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*/
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@Test
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public void Group_By() {
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Collection<Group> results = new GroupBy(postId, postName, commentId).transform(new AbstractProjectable(){
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public CloseableIterator<Object[]> iterate(Expression<?>[] args) {
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assertEquals(postId, args[0]);
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assertEquals(postName, args[1]);
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assertEquals(commentId, args[2]);
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return iterator(
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row(1, "post 1", 1),
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row(2, "post 2", 4),
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row(1, "post 1", 2),
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row(2, "post 2", 5),
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row(3, "post 3", 6),
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row(null, "null post", 7),
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row(null, "null post", 8),
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row(1, "post 1", 3)
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);
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}
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});
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assertEquals(4, results.size());
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Iterator<Group> iter = results.iterator();
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Group g = iter.next();
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assertEquals(toInt(1), g.get(postId));
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assertEquals("post 1", g.get(postName));
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assertEquals(3, g.size());
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List<Integer> comments = g.getList(commentId);
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assertEquals(toInt(1), comments.get(0));
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assertEquals(toInt(2), comments.get(1));
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assertEquals(toInt(3), comments.get(2));
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g = iter.next();
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assertEquals(toInt(2), g.get(postId));
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assertEquals("post 2", g.get(postName));
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assertEquals(2, g.size());
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comments = g.getList(commentId);
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assertEquals(toInt(4), comments.get(0));
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assertEquals(toInt(5), comments.get(1));
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g = iter.next();
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assertEquals(toInt(3), g.get(postId));
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assertEquals("post 3", g.get(postName));
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assertEquals(1, g.size());
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comments = g.getList(commentId);
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assertEquals(toInt(6), comments.get(0));
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// Group by null value
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g = iter.next();
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assertEquals(null, g.get(postId));
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assertEquals("null post", g.get(postName));
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assertEquals(2, g.size());
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comments = g.getList(commentId);
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assertEquals(toInt(7), comments.get(0));
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assertEquals(toInt(8), comments.get(1));
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}
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private Integer toInt(int i) {
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return Integer.valueOf(i);
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}
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private static Object[] row(Object... row) {
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return row;
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}
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private static <T> CloseableIterator<T> iterator(Object[]... rows) {
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return new IteratorAdapter(Arrays.asList(rows).iterator());
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}
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}
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