Merge pull request #1464 from katzyn/window

Assorted minor changes in window processing code

h2/src/main/org/h2/command/dml/SelectGroups.java

@@ -15,6 +15,8 @@ import java.util.Map.Entry;
 import org.h2.engine.Session;
 import org.h2.expression.Expression;
 import org.h2.expression.aggregate.DataAnalysisOperation;
+import org.h2.expression.aggregate.PartitionData;
+import org.h2.util.ValueHashMap;
 import org.h2.value.Value;
 import org.h2.value.ValueArray;
 
@@ -62,12 +64,6 @@ public abstract class SelectGroups {
          */
         private Iterator<Entry<ValueArray, Object[]>> cursor;
 
-        /**
-         * The key for the default group.
-         */
-        // Can be static, but TestClearReferences complains about it
-        private final ValueArray defaultGroup = ValueArray.get(new Value[0]);
-
         Grouped(Session session, ArrayList<Expression> expressions, int[] groupIndex) {
             super(session, expressions);
             this.groupIndex = groupIndex;
@@ -84,7 +80,7 @@ public abstract class SelectGroups {
         @Override
         public void nextSource() {
             if (groupIndex == null) {
-                currentGroupsKey = defaultGroup;
+                currentGroupsKey = ValueArray.getEmpty();
             } else {
                 Value[] keyValues = new Value[groupIndex.length];
                 // update group
@@ -97,7 +93,7 @@ public abstract class SelectGroups {
             }
             Object[] values = groupByData.get(currentGroupsKey);
             if (values == null) {
-                values = new Object[Math.max(exprToIndexInGroupByData.size(), expressions.size())];
+                values = createRow();
                 groupByData.put(currentGroupsKey, values);
             }
             currentGroupByExprData = values;
@@ -118,8 +114,7 @@ public abstract class SelectGroups {
         public void done() {
             super.done();
             if (groupIndex == null && groupByData.size() == 0) {
-                groupByData.put(defaultGroup,
-                        new Object[Math.max(exprToIndexInGroupByData.size(), expressions.size())]);
+                groupByData.put(ValueArray.getEmpty(), createRow());
             }
             cursor = groupByData.entrySet().iterator();
         }
@@ -164,7 +159,7 @@ public abstract class SelectGroups {
 
         @Override
         public void nextSource() {
-            Object[] values = new Object[Math.max(exprToIndexInGroupByData.size(), expressions.size())];
+            Object[] values = createRow();
             rows.add(values);
             currentGroupByExprData = values;
             currentGroupRowId++;
@@ -184,10 +179,9 @@ public abstract class SelectGroups {
         @Override
         public ValueArray next() {
             if (cursor.hasNext()) {
-                Object[] values = cursor.next();
-                currentGroupByExprData = values;
+                currentGroupByExprData = cursor.next();
                 currentGroupRowId++;
-                return ValueArray.get(new Value[0]);
+                return ValueArray.getEmpty();
             }
             return null;
         }
@@ -206,12 +200,17 @@ public abstract class SelectGroups {
      * Maps an expression object to an index, to use in accessing the Object[]
      * pointed to by groupByData.
      */
-    final HashMap<Expression, Integer> exprToIndexInGroupByData = new HashMap<>();
+    private final HashMap<Expression, Integer> exprToIndexInGroupByData = new HashMap<>();
+
+    /**
+     * Maps an window expression object to its data.
+     */
+    private final HashMap<DataAnalysisOperation, PartitionData> windowData = new HashMap<>();
 
     /**
-     * Maps an expression object to its data.
+     * Maps an partitioned window expression object to its data.
      */
-    private final HashMap<DataAnalysisOperation, Object> windowData = new HashMap<>();
+    private final HashMap<DataAnalysisOperation, ValueHashMap<PartitionData>> windowPartitionData = new HashMap<>();
 
     /**
      * The id of the current group.
@@ -286,15 +285,26 @@ public abstract class SelectGroups {
         currentGroupByExprData[index] = obj;
     }
 
+    final Object[] createRow() {
+        return new Object[Math.max(exprToIndexInGroupByData.size(), expressions.size())];
+    }
+
     /**
      * Get the window data for the specified expression.
      *
      * @param expr
      *            expression
+     * @param partitionKey
+     *            a key of partition
      * @return expression data or null
      */
-    public final Object getWindowExprData(DataAnalysisOperation expr) {
-        return windowData.get(expr);
+    public final PartitionData getWindowExprData(DataAnalysisOperation expr, Value partitionKey) {
+        if (partitionKey == null) {
+            return windowData.get(expr);
+        } else {
+            ValueHashMap<PartitionData> map = windowPartitionData.get(expr);
+            return map != null ? map.get(partitionKey) : null;
+        }
     }
 
     /**
@@ -302,12 +312,23 @@ public abstract class SelectGroups {
      *
      * @param expr
      *            expression
+     * @param partitionKey
+     *            a key of partition
      * @param object
-     *            expression data to set
+     *            window expression data to set
      */
-    public final void setWindowExprData(DataAnalysisOperation expr, Object obj) {
-        Object old = windowData.put(expr, obj);
-        assert old == null;
+    public final void setWindowExprData(DataAnalysisOperation expr, Value partitionKey, PartitionData obj) {
+        if (partitionKey == null) {
+            Object old = windowData.put(expr, obj);
+            assert old == null;
+        } else {
+            ValueHashMap<PartitionData> map = windowPartitionData.get(expr);
+            if (map == null) {
+                map = new ValueHashMap<>();
+                windowPartitionData.put(expr, map);
+            }
+            map.put(partitionKey, obj);
+        }
     }
 
     abstract void updateCurrentGroupExprData();
@@ -329,6 +350,7 @@ public abstract class SelectGroups {
         currentGroupByExprData = null;
         exprToIndexInGroupByData.clear();
         windowData.clear();
+        windowPartitionData.clear();
         currentGroupRowId = 0;
     }
 

h2/src/main/org/h2/expression/aggregate/AbstractAggregate.java

@@ -6,6 +6,8 @@
 package org.h2.expression.aggregate;
 
 import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Iterator;
 
 import org.h2.command.dml.Select;
 import org.h2.command.dml.SelectGroups;
@@ -14,6 +16,7 @@ import org.h2.engine.Session;
 import org.h2.expression.Expression;
 import org.h2.table.ColumnResolver;
 import org.h2.table.TableFilter;
+import org.h2.value.Value;
 
 /**
  * A base class for aggregate functions.
@@ -68,14 +71,67 @@ public abstract class AbstractAggregate extends DataAnalysisOperation {
         super.setEvaluatable(tableFilter, b);
     }
 
+    @Override
+    protected void getOrderedResultLoop(Session session, HashMap<Integer, Value> result, ArrayList<Value[]> ordered,
+            int rowIdColumn) {
+        WindowFrame frame = over.getWindowFrame();
+        if (frame == null || frame.isDefault()) {
+            // Aggregate all values before the current row (including)
+            Object aggregateData = createAggregateData();
+            for (Value[] row : ordered) {
+                // Collect values one by one
+                updateFromExpressions(session, aggregateData, row);
+                result.put(row[rowIdColumn].getInt(), getAggregatedValue(session, aggregateData));
+            }
+        } else if (frame.isFullPartition()) {
+            // Aggregate values from the whole partition
+            Object aggregateData = createAggregateData();
+            for (Value[] row : ordered) {
+                updateFromExpressions(session, aggregateData, row);
+            }
+            // All rows have the same value
+            Value value = getAggregatedValue(session, aggregateData);
+            for (Value[] row : ordered) {
+                result.put(row[rowIdColumn].getInt(), value);
+            }
+        } else {
+            // All other types of frames (slow)
+            int size = ordered.size();
+            for (int i = 0; i < size; i++) {
+                Object aggregateData = createAggregateData();
+                for (Iterator<Value[]> iter = frame.iterator(session, ordered, getOverOrderBySort(), i, false); iter
+                        .hasNext();) {
+                    updateFromExpressions(session, aggregateData, iter.next());
+                }
+                result.put(ordered.get(i)[rowIdColumn].getInt(), getAggregatedValue(session, aggregateData));
+            }
+        }
+    }
+
+    /**
+     * Updates the provided aggregate data from the remembered expressions.
+     *
+     * @param session
+     *            the session
+     * @param aggregateData
+     *            aggregate data
+     * @param array
+     *            values of expressions
+     */
+    protected abstract void updateFromExpressions(Session session, Object aggregateData, Value[] array);
+
     @Override
     protected void updateAggregate(Session session, SelectGroups groupData, int groupRowId) {
         if (filterCondition == null || filterCondition.getBooleanValue(session)) {
             ArrayList<SelectOrderBy> orderBy;
-            if (over != null && (orderBy = over.getOrderBy()) != null) {
-                updateOrderedAggregate(session, groupData, groupRowId, orderBy);
+            if (over != null) {
+                if ((orderBy = over.getOrderBy()) != null) {
+                    updateOrderedAggregate(session, groupData, groupRowId, orderBy);
+                } else {
+                    updateAggregate(session, getWindowData(session, groupData, false));
+                }
             } else {
-                updateAggregate(session, getData(session, groupData, false, false));
+                updateAggregate(session, getGroupData(groupData, false));
             }
         }
     }

h2/src/main/org/h2/expression/aggregate/AggregateDataHistogram.java

@@ -38,7 +38,7 @@ class AggregateDataHistogram extends AggregateData {
     @Override
     void add(Database database, int dataType, Value v) {
         if (distinctValues == null) {
-            distinctValues = ValueHashMap.newInstance();
+            distinctValues = new ValueHashMap<>();
         }
         LongDataCounter a = distinctValues.get(v);
         if (a == null) {
@@ -54,7 +54,7 @@ class AggregateDataHistogram extends AggregateData {
     @Override
     Value getValue(Database database, int dataType) {
         if (distinctValues == null) {
-            return ValueArray.get(new Value[0]).convertTo(dataType);
+            return ValueArray.getEmpty().convertTo(dataType);
         }
         ValueArray[] values = new ValueArray[distinctValues.size()];
         int i = 0;

h2/src/main/org/h2/expression/aggregate/AggregateDataMode.java

@@ -25,7 +25,7 @@ class AggregateDataMode extends AggregateData {
             return;
         }
         if (distinctValues == null) {
-            distinctValues = ValueHashMap.newInstance();
+            distinctValues = new ValueHashMap<>();
         }
         LongDataCounter a = distinctValues.get(v);
         if (a == null) {

h2/src/main/org/h2/expression/aggregate/DataAnalysisOperation.java

@@ -8,7 +8,6 @@ package org.h2.expression.aggregate;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
-import java.util.Iterator;
 
 import org.h2.api.ErrorCode;
 import org.h2.command.dml.Select;
@@ -21,9 +20,7 @@ import org.h2.message.DbException;
 import org.h2.result.SortOrder;
 import org.h2.table.ColumnResolver;
 import org.h2.table.TableFilter;
-import org.h2.util.ValueHashMap;
 import org.h2.value.Value;
-import org.h2.value.ValueArray;
 import org.h2.value.ValueInt;
 
 /**
@@ -184,63 +181,28 @@ public abstract class DataAnalysisOperation extends Expression {
      */
     protected abstract void rememberExpressions(Session session, Value[] array);
 
-    /**
-     * Updates the provided aggregate data from the remembered expressions.
-     *
-     * @param session
-     *            the session
-     * @param aggregateData
-     *            aggregate data
-     * @param array
-     *            values of expressions
-     */
-    protected abstract void updateFromExpressions(Session session, Object aggregateData, Value[] array);
-
-    protected Object getData(Session session, SelectGroups groupData, boolean ifExists, boolean forOrderBy) {
+    protected Object getWindowData(Session session, SelectGroups groupData, boolean forOrderBy) {
         Object data;
-        if (over != null) {
-            ValueArray key = over.getCurrentKey(session);
-            if (key != null) {
-                @SuppressWarnings("unchecked")
-                ValueHashMap<Object> map = (ValueHashMap<Object>) groupData.getWindowExprData(this);
-                if (map == null) {
-                    if (ifExists) {
-                        return null;
-                    }
-                    map = new ValueHashMap<>();
-                    groupData.setWindowExprData(this, map);
-                }
-                PartitionData partition = (PartitionData) map.get(key);
-                if (partition == null) {
-                    if (ifExists) {
-                        return null;
-                    }
-                    data = forOrderBy ? new ArrayList<>() : createAggregateData();
-                    map.put(key, new PartitionData(data));
-                } else {
-                    data = partition.getData();
-                }
-            } else {
-                PartitionData partition = (PartitionData) groupData.getWindowExprData(this);
-                if (partition == null) {
-                    if (ifExists) {
-                        return null;
-                    }
-                    data = forOrderBy ? new ArrayList<>() : createAggregateData();
-                    groupData.setWindowExprData(this, new PartitionData(data));
-                } else {
-                    data = partition.getData();
-                }
-            }
+        Value key = over.getCurrentKey(session);
+        PartitionData partition = groupData.getWindowExprData(this, key);
+        if (partition == null) {
+            data = forOrderBy ? new ArrayList<>() : createAggregateData();
+            groupData.setWindowExprData(this, key, new PartitionData(data));
         } else {
-            data = groupData.getCurrentGroupExprData(this);
-            if (data == null) {
-                if (ifExists) {
-                    return null;
-                }
-                data = forOrderBy ? new ArrayList<>() : createAggregateData();
-                groupData.setCurrentGroupExprData(this, data);
+            data = partition.getData();
+        }
+        return data;
+    }
+
+    protected Object getGroupData(SelectGroups groupData, boolean ifExists) {
+        Object data;
+        data = groupData.getCurrentGroupExprData(this);
+        if (data == null) {
+            if (ifExists) {
+                return null;
             }
+            data = createAggregateData();
+            groupData.setCurrentGroupExprData(this, data);
         }
         return data;
     }
@@ -277,43 +239,38 @@ public abstract class DataAnalysisOperation extends Expression {
         if (groupData == null) {
             throw DbException.get(ErrorCode.INVALID_USE_OF_AGGREGATE_FUNCTION_1, getSQL());
         }
-        return over == null ? getAggregatedValue(session, getData(session, groupData, true, false))
+        return over == null ? getAggregatedValue(session, getGroupData(groupData, true))
                 : getWindowResult(session, groupData);
     }
 
+    /**
+     * Returns result of this window function or window aggregate. This method
+     * is not used for plain aggregates.
+     *
+     * @param session
+     *            the session
+     * @param groupData
+     *            the group data
+     * @return result of this function
+     */
     private Value getWindowResult(Session session, SelectGroups groupData) {
         PartitionData partition;
         Object data;
         boolean forOrderBy = over.getOrderBy() != null;
-        ValueArray key = over.getCurrentKey(session);
-        if (key != null) {
-            @SuppressWarnings("unchecked")
-            ValueHashMap<Object> map = (ValueHashMap<Object>) groupData.getWindowExprData(this);
-            if (map == null) {
-                map = new ValueHashMap<>();
-                groupData.setWindowExprData(this, map);
-            }
-            partition = (PartitionData) map.get(key);
-            if (partition == null) {
-                data = forOrderBy ? new ArrayList<>() : createAggregateData();
-                partition = new PartitionData(data);
-                map.put(key, partition);
-            } else {
-                data = partition.getData();
-            }
+        Value key = over.getCurrentKey(session);
+        partition = groupData.getWindowExprData(this, key);
+        if (partition == null) {
+            // Window aggregates with FILTER clause may have no collected values
+            data = forOrderBy ? new ArrayList<>() : createAggregateData();
+            partition = new PartitionData(data);
+            groupData.setWindowExprData(this, key, partition);
         } else {
-            partition = (PartitionData) groupData.getWindowExprData(this);
-            if (partition == null) {
-                data = forOrderBy ? new ArrayList<>() : createAggregateData();
-                partition = new PartitionData(data);
-                groupData.setWindowExprData(this, partition);
-            } else {
-                data = partition.getData();
-            }
+            data = partition.getData();
         }
-        if (over.getOrderBy() != null || !isAggregate()) {
+        if (forOrderBy || !isAggregate()) {
             return getOrderedResult(session, groupData, partition, data);
         }
+        // Window aggregate without ORDER BY clause in window specification
         Value result = partition.getResult();
         if (result == null) {
             result = getAggregatedValue(session, data);
@@ -346,7 +303,7 @@ public abstract class DataAnalysisOperation extends Expression {
         }
         array[ne] = ValueInt.get(groupRowId);
         @SuppressWarnings("unchecked")
-        ArrayList<Value[]> data = (ArrayList<Value[]>) getData(session, groupData, false, true);
+        ArrayList<Value[]> data = (ArrayList<Value[]>) getWindowData(session, groupData, true);
         data.add(array);
     }
 
@@ -378,36 +335,8 @@ public abstract class DataAnalysisOperation extends Expression {
      * @param rowIdColumn
      *            the index of row id value
      */
-    protected void getOrderedResultLoop(Session session, HashMap<Integer, Value> result, ArrayList<Value[]> ordered,
-            int rowIdColumn) {
-        WindowFrame frame = over.getWindowFrame();
-        if (frame == null || frame.isDefault()) {
-            Object aggregateData = createAggregateData();
-            for (Value[] row : ordered) {
-                updateFromExpressions(session, aggregateData, row);
-                result.put(row[rowIdColumn].getInt(), getAggregatedValue(session, aggregateData));
-            }
-        } else if (frame.isFullPartition()) {
-            Object aggregateData = createAggregateData();
-            for (Value[] row : ordered) {
-                updateFromExpressions(session, aggregateData, row);
-            }
-            Value value = getAggregatedValue(session, aggregateData);
-            for (Value[] row : ordered) {
-                result.put(row[rowIdColumn].getInt(), value);
-            }
-        } else {
-            int size = ordered.size();
-            for (int i = 0; i < size; i++) {
-                Object aggregateData = createAggregateData();
-                for (Iterator<Value[]> iter = frame.iterator(session, ordered, getOverOrderBySort(), i, false); iter
-                        .hasNext();) {
-                    updateFromExpressions(session, aggregateData, iter.next());
-                }
-                result.put(ordered.get(i)[rowIdColumn].getInt(), getAggregatedValue(session, aggregateData));
-            }
-        }
-    }
+    protected abstract void getOrderedResultLoop(Session session, HashMap<Integer, Value> result,
+            ArrayList<Value[]> ordered, int rowIdColumn);
 
     protected StringBuilder appendTailConditions(StringBuilder builder) {
         if (over != null) {

h2/src/main/org/h2/expression/aggregate/PartitionData.java

@@ -12,7 +12,7 @@ import org.h2.value.Value;
 /**
  * Partition data of a window aggregate.
  */
-final class PartitionData {
+public final class PartitionData {
 
     /**
      * Aggregate data.

h2/src/main/org/h2/expression/aggregate/Window.java

@@ -185,18 +185,22 @@ public final class Window {
      *            session
      * @return key for the current group, or null
      */
-    public ValueArray getCurrentKey(Session session) {
+    public Value getCurrentKey(Session session) {
         if (partitionBy == null) {
             return null;
         }
         int len = partitionBy.size();
-        Value[] keyValues = new Value[len];
-        // update group
-        for (int i = 0; i < len; i++) {
-            Expression expr = partitionBy.get(i);
-            keyValues[i] = expr.getValue(session);
+        if (len == 1) {
+            return partitionBy.get(0).getValue(session);
+        } else {
+            Value[] keyValues = new Value[len];
+            // update group
+            for (int i = 0; i < len; i++) {
+                Expression expr = partitionBy.get(i);
+                keyValues[i] = expr.getValue(session);
+            }
+            return ValueArray.get(keyValues);
         }
-        return ValueArray.get(keyValues);
     }
 
     /**

h2/src/main/org/h2/expression/aggregate/WindowFunction.java

@@ -174,11 +174,6 @@ public class WindowFunction extends DataAnalysisOperation {
         }
     }
 
-    @Override
-    protected void updateFromExpressions(Session session, Object aggregateData, Value[] array) {
-        throw DbException.getUnsupportedException("Window function");
-    }
-
     @Override
     protected Object createAggregateData() {
         throw DbException.getUnsupportedException("Window function");
@@ -188,62 +183,58 @@ public class WindowFunction extends DataAnalysisOperation {
     protected void getOrderedResultLoop(Session session, HashMap<Integer, Value> result, ArrayList<Value[]> ordered,
             int rowIdColumn) {
         switch (type) {
+        case ROW_NUMBER:
+            for (int i = 0, size = ordered.size(); i < size;) {
+                result.put(ordered.get(i)[rowIdColumn].getInt(), ValueInt.get(++i));
+            }
+            break;
+        case RANK:
+        case DENSE_RANK:
+        case PERCENT_RANK:
+            getRank(result, ordered, rowIdColumn);
+            break;
         case CUME_DIST:
             getCumeDist(session, result, ordered, rowIdColumn);
-            return;
+            break;
         case NTILE:
             getNtile(session, result, ordered, rowIdColumn);
-            return;
+            break;
         case LEAD:
         case LAG:
             getLeadLag(session, result, ordered, rowIdColumn);
-            return;
+            break;
         case FIRST_VALUE:
         case LAST_VALUE:
         case NTH_VALUE:
             getNth(session, result, ordered, rowIdColumn);
-            return;
+            break;
         default:
+            throw DbException.throwInternalError("type=" + type);
         }
+    }
+
+    private void getRank(HashMap<Integer, Value> result, ArrayList<Value[]> ordered, int rowIdColumn) {
         int size = ordered.size();
         int number = 0;
         for (int i = 0; i < size; i++) {
             Value[] row = ordered.get(i);
-            int rowId = row[rowIdColumn].getInt();
-            Value v;
-            switch (type) {
-            case ROW_NUMBER:
-                v = ValueInt.get(i + 1);
-                break;
-            case RANK:
-            case DENSE_RANK:
-            case PERCENT_RANK: {
-                if (i == 0) {
-                    number = 1;
-                } else {
-                    if (getOverOrderBySort().compare(ordered.get(i - 1), row) != 0) {
-                        switch (type) {
-                        case RANK:
-                        case PERCENT_RANK:
-                            number = i + 1;
-                            break;
-                        default: // DENSE_RANK
-                            number++;
-                        }
-                    }
-                }
-                if (type == WindowFunctionType.PERCENT_RANK) {
-                    int nm = number - 1;
-                    v = nm == 0 ? ValueDouble.ZERO : ValueDouble.get((double) nm / (size - 1));
+            if (i == 0) {
+                number = 1;
+            } else if (getOverOrderBySort().compare(ordered.get(i - 1), row) != 0) {
+                if (type == WindowFunctionType.DENSE_RANK) {
+                    number++;
                 } else {
-                    v = ValueInt.get(number);
+                    number = i + 1;
                 }
-                break;
             }
-            default:
-                throw DbException.throwInternalError("type=" + type);
+            Value v;
+            if (type == WindowFunctionType.PERCENT_RANK) {
+                int nm = number - 1;
+                v = nm == 0 ? ValueDouble.ZERO : ValueDouble.get((double) nm / (size - 1));
+            } else {
+                v = ValueInt.get(number);
             }
-            result.put(rowId, v);
+            result.put(row[rowIdColumn].getInt(), v);
         }
     }
 

h2/src/main/org/h2/index/HashIndex.java

@@ -40,7 +40,7 @@ public class HashIndex extends BaseIndex {
     }
 
     private void reset() {
-        rows = ValueHashMap.newInstance();
+        rows = new ValueHashMap<>();
     }
 
     @Override

h2/src/main/org/h2/index/NonUniqueHashIndex.java

@@ -45,7 +45,7 @@ public class NonUniqueHashIndex extends BaseIndex {
     }
 
     private void reset() {
-        rows = ValueHashMap.newInstance();
+        rows = new ValueHashMap<>();
         rowCount = 0;
     }
 

h2/src/main/org/h2/result/LocalResultImpl.java

@@ -147,7 +147,7 @@ public class LocalResultImpl implements LocalResult {
     public void setDistinct() {
         assert distinctIndexes == null;
         distinct = true;
-        distinctRows = ValueHashMap.newInstance();
+        distinctRows = new ValueHashMap<>();
     }
 
     /**
@@ -159,7 +159,7 @@ public class LocalResultImpl implements LocalResult {
     public void setDistinct(int[] distinctIndexes) {
         assert !distinct;
         this.distinctIndexes = distinctIndexes;
-        distinctRows = ValueHashMap.newInstance();
+        distinctRows = new ValueHashMap<>();
     }
 
     /**
@@ -202,7 +202,7 @@ public class LocalResultImpl implements LocalResult {
             return external.contains(values);
         }
         if (distinctRows == null) {
-            distinctRows = ValueHashMap.newInstance();
+            distinctRows = new ValueHashMap<>();
             for (Value[] row : rows) {
                 ValueArray array = getArrayOfDistinct(row);
                 distinctRows.put(array, array.getList());

h2/src/main/org/h2/util/ValueHashMap.java

@@ -38,15 +38,6 @@ public class ValueHashMap<V> extends HashBase {
     Value[] keys;
     V[] values;
 
-    /**
-     * Create a new value hash map.
-     *
-     * @return the object
-     */
-    public static <T> ValueHashMap<T> newInstance() {
-        return new ValueHashMap<>();
-    }
-
     @Override
     @SuppressWarnings("unchecked")
     protected void reset(int newLevel) {

h2/src/main/org/h2/value/ValueArray.java

@@ -20,6 +20,11 @@ import org.h2.util.StatementBuilder;
  */
 public class ValueArray extends Value {
 
+    /**
+     * Empty array.
+     */
+    private static final Object EMPTY = get(new Value[0]);
+
     private final Class<?> componentType;
     private final Value[] values;
     private int hash;
@@ -52,6 +57,15 @@ public class ValueArray extends Value {
         return new ValueArray(componentType, list);
     }
 
+    /**
+     * Returns empty array.
+     *
+     * @return empty array
+     */
+    public static ValueArray getEmpty() {
+        return (ValueArray) EMPTY;
+    }
+
     @Override
     public int hashCode() {
         if (hash != 0) {

h2/src/test/org/h2/test/scripts/functions/aggregate/count.sql

@@ -83,3 +83,14 @@ SELECT I, V, COUNT(V) OVER W C, COUNT(DISTINCT V) OVER W D FROM
 > 6 2 6 2
 > 7 3 7 3
 > rows (ordered): 7
+
+SELECT I, C, COUNT(I) OVER (PARTITION BY C) CNT FROM
+    VALUES (1, 1), (2, 1), (3, 2), (4, 2), (5, 2) T(I, C);
+> I C CNT
+> - - ---
+> 1 1 2
+> 2 1 2
+> 3 2 3
+> 4 2 3
+> 5 2 3
+> rows: 5

h2/src/test/org/h2/test/scripts/functions/window/lead.sql

@@ -143,3 +143,11 @@ SELECT LAG(VALUE) OVER (ORDER BY ID RANGE CURRENT ROW) FROM TEST;
 
 DROP TABLE TEST;
 > ok
+
+SELECT C, SUM(I) S, LEAD(SUM(I)) OVER (ORDER /**/ BY SUM(I)) L FROM
+    VALUES (1, 1), (2, 1), (4, 2), (8, 2) T(I, C) GROUP BY C;
+> C S  L
+> - -- ----
+> 1 3  12
+> 2 12 null
+> rows: 2

h2/src/test/org/h2/test/scripts/functions/window/row_number.sql

@@ -133,7 +133,7 @@ INSERT INTO TEST VALUES
     (4, 'b', 8);
 > update count: 4
 
-SELECT ROW_NUMBER() OVER(ORDER /**/ BY TYPE) RN, TYPE, SUM(CNT) SUM FROM TEST GROUP BY TYPE;
+SELECT ROW_NUMBER() OVER (ORDER /**/ BY TYPE) RN, TYPE, SUM(CNT) SUM FROM TEST GROUP BY TYPE;
 > RN TYPE SUM
 > -- ---- ---
 > 1  a    1
@@ -141,6 +141,16 @@ SELECT ROW_NUMBER() OVER(ORDER /**/ BY TYPE) RN, TYPE, SUM(CNT) SUM FROM TEST GR
 > 3  c    4
 > rows: 3
 
+SELECT A, B, C, ROW_NUMBER() OVER (PARTITION BY A, B) N FROM
+    VALUES (1, 1, 1), (1, 1, 2), (1, 2, 3), (2, 1, 4) T(A, B, C);
+> A B C N
+> - - - -
+> 1 1 1 1
+> 1 1 2 2
+> 1 2 3 1
+> 2 1 4 1
+> rows: 4
+
 SELECT RANK () OVER () FROM TEST;
 > exception SYNTAX_ERROR_2
 
@@ -149,3 +159,9 @@ SELECT DENSE_RANK () OVER () FROM TEST;
 
 DROP TABLE TEST;
 > ok
+
+SELECT ROW_NUMBER() OVER () FROM VALUES (1);
+> ROW_NUMBER() OVER ()
+> --------------------
+> 1
+> rows: 1

h2/src/test/org/h2/test/unit/TestValueHashMap.java

@@ -47,7 +47,7 @@ public class TestValueHashMap extends TestBase implements DataHandler {
     }
 
     private void testNotANumber() {
-        ValueHashMap<Integer> map = ValueHashMap.newInstance();
+        ValueHashMap<Integer> map = new ValueHashMap<>();
         for (int i = 1; i < 100; i++) {
             double d = Double.longBitsToDouble(0x7ff0000000000000L | i);
             ValueDouble v = ValueDouble.get(d);
@@ -57,7 +57,7 @@ public class TestValueHashMap extends TestBase implements DataHandler {
     }
 
     private void testRandomized() {
-        ValueHashMap<Value> map = ValueHashMap.newInstance();
+        ValueHashMap<Value> map = new ValueHashMap<>();
         HashMap<Value, Value> hash = new HashMap<>();
         Random random = new Random(1);
         Comparator<Value> vc = new Comparator<Value>() {