Merge pull request #1408 from katzyn/aggregate

Add MODE() aggregate function

h2/src/docsrc/help/help.csv

@@ -3416,6 +3416,27 @@ Aggregates are only allowed in select statements.
 MEDIAN(X)
 "
 
+"Functions (Aggregate)","MODE","
+{ MODE( value ) [ ORDER BY expression [ ASC | DESC ] ] }
+    | { MODE() WITHIN GROUP(ORDER BY expression [ ASC | DESC ]) }
+[ FILTER ( WHERE expression ) ]
+","
+Returns the value that occurs with the greatest frequency.
+If there are multiple values with the same frequency only one value will be returned.
+In this situation value will be chosen based on optional ORDER BY clause
+that should specify exactly the same expression as argument of this function.
+Use ascending order to get smallest value or descending order to get largest value
+from multiple values with the same frequency.
+If this clause is not specified the exact chosen value is not determined in this situation.
+NULL values are ignored in the calculation.
+If no rows are selected, the result is NULL.
+Aggregates are only allowed in select statements.
+","
+MODE(X)
+MODE(X ORDER BY X)
+MODE() WITHIN GROUP(ORDER BY X)
+"
+
 "Functions (Numeric)","ABS","
 ABS ( { numeric } )
 ","

h2/src/docsrc/html/changelog.html

@@ -21,6 +21,14 @@ Change Log
 
 <h2>Next Version (unreleased)</h2>
 <ul>
+<li>Issue #1407: Add a MODE() aggregate function
+</li>
+<li>PR #1402: Duplicate conditions in column check constraint
+</li>
+<li>PR #1399: Add more subclasses of SQLException and use it for some error codes
+</li>
+<li>PR #1397: Add DATEADD return type detection
+</li>
 <li>Issue #1393: Add INFORMATION_SCHEMA.COLUMNS.IS_VISIBLE
 </li>
 <li>PR #1392: Some refactoring and assorted minor optimizations

h2/src/main/org/h2/api/ErrorCode.java

@@ -402,6 +402,17 @@ public class ErrorCode {
      */
     public static final int COLUMN_NOT_FOUND_1 = 42122;
 
+    /**
+     * The error with code <code>42123</code> is thrown when
+     * identical expressions should be used, but different
+     * exceptions were found.
+     * Example:
+     * <pre>
+     * SELECT MODE(A ORDER BY B) FROM TEST;
+     * </pre>
+     */
+    public static final int IDENTICAL_EXPRESSIONS_SHOULD_BE_USED = 42131;
+
     // 0A: feature not supported
 
     // HZ: remote database access
@@ -2068,6 +2079,7 @@ public class ErrorCode {
         case INDEX_NOT_FOUND_1: return "42S12";
         case DUPLICATE_COLUMN_NAME_1: return "42S21";
         case COLUMN_NOT_FOUND_1: return "42S22";
+        case IDENTICAL_EXPRESSIONS_SHOULD_BE_USED: return "42S31";
 
         // 0A: feature not supported
 

h2/src/main/org/h2/command/Parser.java

@@ -145,8 +145,6 @@ import org.h2.engine.SysProperties;
 import org.h2.engine.User;
 import org.h2.engine.UserAggregate;
 import org.h2.engine.UserDataType;
-import org.h2.expression.Aggregate;
-import org.h2.expression.Aggregate.AggregateType;
 import org.h2.expression.Alias;
 import org.h2.expression.BinaryOperation;
 import org.h2.expression.BinaryOperation.OpType;
@@ -163,7 +161,6 @@ import org.h2.expression.ExpressionColumn;
 import org.h2.expression.ExpressionList;
 import org.h2.expression.Function;
 import org.h2.expression.FunctionCall;
-import org.h2.expression.JavaAggregate;
 import org.h2.expression.JavaFunction;
 import org.h2.expression.Parameter;
 import org.h2.expression.Rownum;
@@ -174,6 +171,9 @@ import org.h2.expression.UnaryOperation;
 import org.h2.expression.ValueExpression;
 import org.h2.expression.Variable;
 import org.h2.expression.Wildcard;
+import org.h2.expression.aggregate.Aggregate;
+import org.h2.expression.aggregate.Aggregate.AggregateType;
+import org.h2.expression.aggregate.JavaAggregate;
 import org.h2.index.Index;
 import org.h2.message.DbException;
 import org.h2.result.SortOrder;
@@ -1209,12 +1209,7 @@ public class Parser {
     }
 
     private int parseSortType() {
-        int sortType = 0;
-        if (readIf("ASC")) {
-            // ignore
-        } else if (readIf("DESC")) {
-            sortType = SortOrder.DESCENDING;
-        }
+        int sortType = parseSimpleSortType();
         if (readIf("NULLS")) {
             if (readIf("FIRST")) {
                 sortType |= SortOrder.NULLS_FIRST;
@@ -1226,6 +1221,13 @@ public class Parser {
         return sortType;
     }
 
+    private int parseSimpleSortType() {
+        if (!readIf("ASC") && readIf("DESC")) {
+            return SortOrder.DESCENDING;
+        }
+        return SortOrder.ASCENDING;
+    }
+
     private String[] parseColumnList() {
         ArrayList<String> columns = Utils.newSmallArrayList();
         do {
@@ -2916,40 +2918,35 @@ public class Parser {
         }
         currentSelect.setGroupQuery();
         Aggregate r;
-        if (aggregateType == AggregateType.COUNT) {
+        switch (aggregateType) {
+        case COUNT:
             if (readIf(ASTERISK)) {
-                r = new Aggregate(AggregateType.COUNT_ALL, null, currentSelect,
-                        false);
+                r = new Aggregate(AggregateType.COUNT_ALL, null, currentSelect, false);
             } else {
                 boolean distinct = readIf(DISTINCT);
                 Expression on = readExpression();
                 if (on instanceof Wildcard && !distinct) {
                     // PostgreSQL compatibility: count(t.*)
-                    r = new Aggregate(AggregateType.COUNT_ALL, null, currentSelect,
-                            false);
+                    r = new Aggregate(AggregateType.COUNT_ALL, null, currentSelect, false);
                 } else {
-                    r = new Aggregate(AggregateType.COUNT, on, currentSelect,
-                            distinct);
+                    r = new Aggregate(AggregateType.COUNT, on, currentSelect, distinct);
                 }
             }
-        } else if (aggregateType == AggregateType.GROUP_CONCAT) {
+            break;
+        case GROUP_CONCAT: {
             boolean distinct = readIf(DISTINCT);
-
             if (equalsToken("GROUP_CONCAT", aggregateName)) {
-                r = new Aggregate(AggregateType.GROUP_CONCAT,
-                    readExpression(), currentSelect, distinct);
+                r = new Aggregate(AggregateType.GROUP_CONCAT, readExpression(), currentSelect, distinct);
                 if (readIf(ORDER)) {
                     read("BY");
                     r.setOrderByList(parseSimpleOrderList());
                 }
-
                 if (readIf("SEPARATOR")) {
                     r.setGroupConcatSeparator(readExpression());
                 }
             } else if (equalsToken("STRING_AGG", aggregateName)) {
                 // PostgreSQL compatibility: string_agg(expression, delimiter)
-                r = new Aggregate(AggregateType.GROUP_CONCAT,
-                    readExpression(), currentSelect, distinct);
+                r = new Aggregate(AggregateType.GROUP_CONCAT, readExpression(), currentSelect, distinct);
                 read(COMMA);
                 r.setGroupConcatSeparator(readExpression());
                 if (readIf(ORDER)) {
@@ -2959,19 +2956,47 @@ public class Parser {
             } else {
                 r = null;
             }
-        } else if (aggregateType == AggregateType.ARRAY_AGG) {
+            break;
+        }
+        case ARRAY_AGG: {
             boolean distinct = readIf(DISTINCT);
-
-            r = new Aggregate(AggregateType.ARRAY_AGG,
-                readExpression(), currentSelect, distinct);
+            r = new Aggregate(AggregateType.ARRAY_AGG, readExpression(), currentSelect, distinct);
             if (readIf(ORDER)) {
                 read("BY");
                 r.setOrderByList(parseSimpleOrderList());
             }
+            break;
+        }
+        case MODE: {
+            if (readIf(CLOSE_PAREN)) {
+                read("WITHIN");
+                read(GROUP);
+                read(OPEN_PAREN);
+                read(ORDER);
+                read("BY");
+                Expression expr = readExpression();
+                r = new Aggregate(AggregateType.MODE, expr, currentSelect, false);
+                setModeAggOrder(r, expr);
             } else {
+                Expression expr = readExpression();
+                r = new Aggregate(aggregateType, expr, currentSelect, false);
+                if (readIf(ORDER)) {
+                    read("BY");
+                    Expression expr2 = readExpression();
+                    String sql = expr.getSQL(), sql2 = expr2.getSQL();
+                    if (!sql.equals(sql2)) {
+                        throw DbException.getSyntaxError(ErrorCode.IDENTICAL_EXPRESSIONS_SHOULD_BE_USED, sqlCommand,
+                                lastParseIndex, sql, sql2);
+                    }
+                    setModeAggOrder(r, expr);
+                }
+            }
+            break;
+        }
+        default:
             boolean distinct = readIf(DISTINCT);
-            r = new Aggregate(aggregateType, readExpression(), currentSelect,
-                    distinct);
+            r = new Aggregate(aggregateType, readExpression(), currentSelect, distinct);
+            break;
         }
         read(CLOSE_PAREN);
         if (r != null) {
@@ -2980,6 +3005,15 @@ public class Parser {
         return r;
     }
 
+    private void setModeAggOrder(Aggregate r, Expression expr) {
+        ArrayList<SelectOrderBy> orderList = new ArrayList<>(1);
+        SelectOrderBy order = new SelectOrderBy();
+        order.expression = expr;
+        order.sortType = parseSimpleSortType();
+        orderList.add(order);
+        r.setOrderByList(orderList);
+    }
+
     private ArrayList<SelectOrderBy> parseSimpleOrderList() {
         ArrayList<SelectOrderBy> orderList = Utils.newSmallArrayList();
         do {

h2/src/main/org/h2/expression/Aggregate.java → h2/src/main/org/h2/expression/aggregate/Aggregate.java

@@ -3,7 +3,7 @@
  * and the EPL 1.0 (http://h2database.com/html/license.html).
  * Initial Developer: H2 Group
  */
-package org.h2.expression;
+package org.h2.expression.aggregate;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -13,6 +13,9 @@ import org.h2.api.ErrorCode;
 import org.h2.command.dml.Select;
 import org.h2.command.dml.SelectOrderBy;
 import org.h2.engine.Session;
+import org.h2.expression.Expression;
+import org.h2.expression.ExpressionColumn;
+import org.h2.expression.ExpressionVisitor;
 import org.h2.index.Cursor;
 import org.h2.index.Index;
 import org.h2.message.DbException;
@@ -129,10 +132,16 @@ public class Aggregate extends Expression {
          * The aggregate type for MEDIAN(expression).
          */
         MEDIAN,
+
         /**
          * The aggregate type for ARRAY_AGG(expression).
          */
-        ARRAY_AGG
+        ARRAY_AGG,
+
+        /**
+         * The aggregate type for MODE(expression).
+         */
+        MODE,
     }
 
     private static final HashMap<String, AggregateType> AGGREGATES = new HashMap<>(64);
@@ -200,6 +209,9 @@ public class Aggregate extends Expression {
         addAggregate("BIT_AND", AggregateType.BIT_AND);
         addAggregate("MEDIAN", AggregateType.MEDIAN);
         addAggregate("ARRAY_AGG", AggregateType.ARRAY_AGG);
+        addAggregate("MODE", AggregateType.MODE);
+        // Oracle compatibility
+        addAggregate("STATS_MODE", AggregateType.MODE);
     }
 
     private static void addAggregate(String name, AggregateType type) {
@@ -372,7 +384,8 @@ public class Aggregate extends Expression {
             data = AggregateData.create(type);
             select.setCurrentGroupExprData(this, data);
         }
-        if (type == AggregateType.GROUP_CONCAT) {
+        switch (type) {
+        case GROUP_CONCAT: {
             Value[] array = ((AggregateDataCollecting) data).getArray();
             if (array == null) {
                 return ValueNull.INSTANCE;
@@ -399,7 +412,8 @@ public class Aggregate extends Expression {
                 buff.append(s);
             }
             return ValueString.get(buff.toString());
-        } else if (type == AggregateType.ARRAY_AGG) {
+        }
+        case ARRAY_AGG: {
             Value[] array = ((AggregateDataCollecting) data).getArray();
             if (array == null) {
                 return ValueNull.INSTANCE;
@@ -414,8 +428,16 @@ public class Aggregate extends Expression {
             }
             return ValueArray.get(array);
         }
+        case MODE:
+            if (orderByList != null) {
+                return ((AggregateDataMode) data).getOrderedValue(session.getDatabase(), dataType,
+                        (orderByList.get(0).sortType & SortOrder.DESCENDING) != 0);
+            }
+            //$FALL-THROUGH$
+        default:
             return data.getValue(session.getDatabase(), dataType, distinct);
         }
+    }
 
     @Override
     public int getType() {
@@ -503,6 +525,7 @@ public class Aggregate extends Expression {
         case MIN:
         case MAX:
         case MEDIAN:
+        case MODE:
             break;
         case STDDEV_POP:
         case STDDEV_SAMP:
@@ -673,6 +696,9 @@ public class Aggregate extends Expression {
             break;
         case ARRAY_AGG:
             return getSQLArrayAggregate();
+        case MODE:
+            text = "MODE";
+            break;
         default:
             throw DbException.throwInternalError("type=" + type);
         }

h2/src/main/org/h2/expression/AggregateData.java → h2/src/main/org/h2/expression/aggregate/AggregateData.java

@@ -3,10 +3,10 @@
  * and the EPL 1.0 (http://h2database.com/html/license.html).
  * Initial Developer: H2 Group
  */
-package org.h2.expression;
+package org.h2.expression.aggregate;
 
 import org.h2.engine.Database;
-import org.h2.expression.Aggregate.AggregateType;
+import org.h2.expression.aggregate.Aggregate.AggregateType;
 import org.h2.value.Value;
 
 /**
@@ -35,6 +35,8 @@ abstract class AggregateData {
             return new AggregateDataHistogram();
         case MEDIAN:
             return new AggregateDataMedian();
+        case MODE:
+            return new AggregateDataMode();
         default:
             return new AggregateDataDefault(aggregateType);
         }

h2/src/main/org/h2/expression/AggregateDataCollecting.java → h2/src/main/org/h2/expression/aggregate/AggregateDataCollecting.java

@@ -3,7 +3,7 @@
  * and the EPL 1.0 (http://h2database.com/html/license.html).
  * Initial Developer: H2 Group
  */
-package org.h2.expression;
+package org.h2.expression.aggregate;
 
 import java.util.ArrayList;
 import java.util.Collection;

h2/src/main/org/h2/expression/AggregateDataCount.java → h2/src/main/org/h2/expression/aggregate/AggregateDataCount.java

@@ -3,7 +3,7 @@
  * and the EPL 1.0 (http://h2database.com/html/license.html).
  * Initial Developer: H2 Group
  */
-package org.h2.expression;
+package org.h2.expression.aggregate;
 
 import org.h2.engine.Database;
 import org.h2.util.ValueHashMap;

h2/src/main/org/h2/expression/AggregateDataCountAll.java → h2/src/main/org/h2/expression/aggregate/AggregateDataCountAll.java

@@ -3,7 +3,7 @@
  * and the EPL 1.0 (http://h2database.com/html/license.html).
  * Initial Developer: H2 Group
  */
-package org.h2.expression;
+package org.h2.expression.aggregate;
 
 import org.h2.engine.Database;
 import org.h2.message.DbException;

h2/src/main/org/h2/expression/AggregateDataDefault.java → h2/src/main/org/h2/expression/aggregate/AggregateDataDefault.java

@@ -3,10 +3,10 @@
  * and the EPL 1.0 (http://h2database.com/html/license.html).
  * Initial Developer: H2 Group
  */
-package org.h2.expression;
+package org.h2.expression.aggregate;
 
 import org.h2.engine.Database;
-import org.h2.expression.Aggregate.AggregateType;
+import org.h2.expression.aggregate.Aggregate.AggregateType;
 import org.h2.message.DbException;
 import org.h2.util.ValueHashMap;
 import org.h2.value.DataType;

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

@@ -3,11 +3,11 @@
  * and the EPL 1.0 (http://h2database.com/html/license.html).
  * Initial Developer: H2 Group
  */
-package org.h2.expression;
+package org.h2.expression.aggregate;
 
 import java.util.Arrays;
 import java.util.Comparator;
-import java.util.Map;
+import java.util.Map.Entry;
 import org.h2.engine.Constants;
 import org.h2.engine.Database;
 import org.h2.engine.Mode;
@@ -21,37 +21,35 @@ import org.h2.value.ValueLong;
  * Data stored while calculating a HISTOGRAM aggregate.
  */
 class AggregateDataHistogram extends AggregateData {
-    private long count;
-    private ValueHashMap<AggregateDataHistogram> distinctValues;
+
+    private ValueHashMap<LongDataCounter> distinctValues;
 
     @Override
     void add(Database database, int dataType, boolean distinct, Value v) {
         if (distinctValues == null) {
             distinctValues = ValueHashMap.newInstance();
         }
-        AggregateDataHistogram a = distinctValues.get(v);
+        LongDataCounter a = distinctValues.get(v);
         if (a == null) {
-            if (distinctValues.size() < Constants.SELECTIVITY_DISTINCT_COUNT) {
-                a = new AggregateDataHistogram();
-                distinctValues.put(v, a);
+            if (distinctValues.size() >= Constants.SELECTIVITY_DISTINCT_COUNT) {
+                return;
             }
+            a = new LongDataCounter();
+            distinctValues.put(v, a);
         }
-        if (a != null) {
         a.count++;
     }
-    }
 
     @Override
     Value getValue(Database database, int dataType, boolean distinct) {
-        if (distinct) {
-            count = 0;
-            groupDistinct(database, dataType);
+        if (distinctValues == null) {
+            return ValueArray.get(new Value[0]).convertTo(dataType);
         }
         ValueArray[] values = new ValueArray[distinctValues.size()];
         int i = 0;
-        for (Map.Entry<Value,AggregateDataHistogram> entry : distinctValues.entries()) {
-            AggregateDataHistogram d = entry.getValue();
-            values[i] = ValueArray.get(new Value[] { entry.getKey(), ValueLong.get(d.count) });
+        for (Entry<Value, LongDataCounter> entry : distinctValues.entries()) {
+            LongDataCounter d = entry.getValue();
+            values[i] = ValueArray.get(new Value[] { entry.getKey(), ValueLong.get(distinct ? 1L : d.count) });
             i++;
         }
         final Mode mode = database.getMode();
@@ -64,18 +62,7 @@ class AggregateDataHistogram extends AggregateData {
                 return a1.compareTo(a2, mode, compareMode);
             }
         });
-        Value v = ValueArray.get(values);
-        return v.convertTo(dataType);
-    }
-
-    private void groupDistinct(Database database, int dataType) {
-        if (distinctValues == null) {
-            return;
-        }
-        count = 0;
-        for (Value v : distinctValues.keys()) {
-            add(database, dataType, false, v);
-        }
+        return ValueArray.get(values).convertTo(dataType);
     }
 
 }

h2/src/main/org/h2/expression/AggregateDataMedian.java → h2/src/main/org/h2/expression/aggregate/AggregateDataMedian.java

@@ -3,7 +3,7 @@
  * and the EPL 1.0 (http://h2database.com/html/license.html).
  * Initial Developer: H2 Group
  */
-package org.h2.expression;
+package org.h2.expression.aggregate;
 
 import java.math.BigDecimal;
 import java.util.ArrayList;
@@ -14,6 +14,8 @@ import org.h2.engine.Database;
 import org.h2.engine.Mode;
 import org.h2.engine.Session;
 import org.h2.engine.SysProperties;
+import org.h2.expression.Expression;
+import org.h2.expression.ExpressionColumn;
 import org.h2.index.Cursor;
 import org.h2.index.Index;
 import org.h2.result.SearchRow;

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

+/*
+ * Copyright 2004-2018 H2 Group. Multiple-Licensed under the MPL 2.0,
+ * and the EPL 1.0 (http://h2database.com/html/license.html).
+ * Initial Developer: H2 Group
+ */
+package org.h2.expression.aggregate;
+
+import java.util.Map.Entry;
+
+import org.h2.engine.Database;
+import org.h2.util.ValueHashMap;
+import org.h2.value.Value;
+import org.h2.value.ValueNull;
+
+/**
+ * Data stored while calculating a MODE aggregate.
+ */
+class AggregateDataMode extends AggregateData {
+
+    private ValueHashMap<LongDataCounter> distinctValues;
+
+    @Override
+    void add(Database database, int dataType, boolean distinct, Value v) {
+        if (v == ValueNull.INSTANCE) {
+            return;
+        }
+        if (distinctValues == null) {
+            distinctValues = ValueHashMap.newInstance();
+        }
+        LongDataCounter a = distinctValues.get(v);
+        if (a == null) {
+            a = new LongDataCounter();
+            distinctValues.put(v, a);
+        }
+        a.count++;
+    }
+
+    @Override
+    Value getValue(Database database, int dataType, boolean distinct) {
+        Value v = ValueNull.INSTANCE;
+        if (distinctValues != null) {
+            long count = 0L;
+            for (Entry<Value, LongDataCounter> entry : distinctValues.entries()) {
+                long c = entry.getValue().count;
+                if (c > count) {
+                    v = entry.getKey();
+                    count = c;
+                }
+            }
+        }
+        return v.convertTo(dataType);
+    }
+
+    Value getOrderedValue(Database database, int dataType, boolean desc) {
+        Value v = ValueNull.INSTANCE;
+        if (distinctValues != null) {
+            long count = 0L;
+            for (Entry<Value, LongDataCounter> entry : distinctValues.entries()) {
+                long c = entry.getValue().count;
+                if (c > count) {
+                    v = entry.getKey();
+                    count = c;
+                } else if (c == count) {
+                    Value v2 = entry.getKey();
+                    int cmp = database.compareTypeSafe(v, v2);
+                    if (desc) {
+                        if (cmp >= 0) {
+                            continue;
+                        }
+                    } else if (cmp <= 0) {
+                        continue;
+                    }
+                    v = v2;
+                }
+            }
+        }
+        return v.convertTo(dataType);
+    }
+
+}

h2/src/main/org/h2/expression/AggregateDataSelectivity.java → h2/src/main/org/h2/expression/aggregate/AggregateDataSelectivity.java

@@ -3,7 +3,7 @@
  * and the EPL 1.0 (http://h2database.com/html/license.html).
  * Initial Developer: H2 Group
  */
-package org.h2.expression;
+package org.h2.expression.aggregate;
 
 import org.h2.engine.Constants;
 import org.h2.engine.Database;

h2/src/main/org/h2/expression/JavaAggregate.java → h2/src/main/org/h2/expression/aggregate/JavaAggregate.java

@@ -3,7 +3,7 @@
  * and the EPL 1.0 (http://h2database.com/html/license.html).
  * Initial Developer: H2 Group
  */
-package org.h2.expression;
+package org.h2.expression.aggregate;
 
 import java.sql.Connection;
 import java.sql.SQLException;
@@ -13,6 +13,8 @@ import org.h2.command.Parser;
 import org.h2.command.dml.Select;
 import org.h2.engine.Session;
 import org.h2.engine.UserAggregate;
+import org.h2.expression.Expression;
+import org.h2.expression.ExpressionVisitor;
 import org.h2.message.DbException;
 import org.h2.table.ColumnResolver;
 import org.h2.table.TableFilter;

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

+/*
+ * Copyright 2004-2018 H2 Group. Multiple-Licensed under the MPL 2.0,
+ * and the EPL 1.0 (http://h2database.com/html/license.html).
+ * Initial Developer: H2 Group
+ */
+package org.h2.expression.aggregate;
+
+/**
+ * Counter.
+ */
+final class LongDataCounter {
+
+    /**
+     * The value.
+     */
+    long count;
+
+}

h2/src/main/org/h2/expression/aggregate/package.html

+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+<!--
+Copyright 2004-2018 H2 Group. Multiple-Licensed under the MPL 2.0, Version 1.0,
+and under the Eclipse Public License, Version 1.0
+Initial Developer: H2 Group
+-->
+<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
+<head><meta http-equiv="Content-Type" content="text/html;charset=utf-8" /><title>
+Javadoc package documentation
+</title></head><body style="font: 9pt/130% Tahoma, Arial, Helvetica, sans-serif; font-weight: normal;"><p>
+
+Aggregate functions.
+
+</p></body></html>
\ No newline at end of file

h2/src/main/org/h2/message/DbException.java

@@ -237,6 +237,22 @@ public class DbException extends RuntimeException {
                 null, sql, message));
     }
 
+    /**
+     * Create a syntax error exception for a specific error code.
+     *
+     * @param errorCode the error code
+     * @param sql the SQL statement
+     * @param index the position of the error in the SQL statement
+     * @param params the list of parameters of the message
+     * @return the exception
+     */
+    public static DbException getSyntaxError(int errorCode, String sql, int index, String... params) {
+        sql = StringUtils.addAsterisk(sql, index);
+        String sqlstate = ErrorCode.getState(errorCode);
+        String message = translate(sqlstate, params);
+        return new DbException(getJdbcSQLException(message, sql, sqlstate, errorCode, null, null));
+    }
+
     /**
      * Gets a SQL exception meaning this feature is not supported.
      *

h2/src/main/org/h2/res/_messages_cs.prop

@@ -31,7 +31,7 @@
 42S12=Index {0} nenalezen
 42S21=Duplicitní název sloupce {0}
 42S22=Sloupec {0} nenalezen
-42S32=Nastavení {0} nenalezeno
+42S31=#Identical expressions should be used; expected {0}, found {1}
 57014=Příkaz byl zrušen nebo připojení vypršelo
 90000=Funkce {0} musí vracet výsledek
 90001=Metoda neumožňuje dotazování. Použijte execute nebo executeQuery namísto executeUpdate

h2/src/main/org/h2/res/_messages_de.prop

@@ -31,7 +31,7 @@
 42S12=Index {0} nicht gefunden
 42S21=Doppelter Feldname {0}
 42S22=Feld {0} nicht gefunden
-42S32=Einstellung {0} nicht gefunden
+42S31=#Identical expressions should be used; expected {0}, found {1}
 57014=Befehl wurde abgebrochen oder das Session-Timeout ist abgelaufen
 90000=Funktion {0} muss Zeilen zurückgeben
 90001=Methode nicht zulässig für eine Abfrage. Erlaubt sind execute oder executeQuery, nicht jedoch executeUpdate

h2/src/main/org/h2/res/_messages_en.prop

@@ -31,7 +31,7 @@
 42S12=Index {0} not found
 42S21=Duplicate column name {0}
 42S22=Column {0} not found
-42S32=Setting {0} not found
+42S31=Identical expressions should be used; expected {0}, found {1}
 57014=Statement was canceled or the session timed out
 90000=Function {0} must return a result set
 90001=Method is not allowed for a query. Use execute or executeQuery instead of executeUpdate

h2/src/main/org/h2/res/_messages_es.prop

@@ -31,7 +31,7 @@
 42S12=Indice {0} no encontrado
 42S21=Nombre de columna Duplicada {0}
 42S22=Columna {0} no encontrada
-42S32=Setting {0} no encontrado
+42S31=#Identical expressions should be used; expected {0}, found {1}
 57014=Ls sentencia fue cancelado ó la sesión expiró por tiempo vencido
 90000=Función {0} debe devolver un set de resultados (ResultSet)
 90001=Metodo no permitido en un query. Use execute ó executeQuery en lugar de executeUpdate

h2/src/main/org/h2/res/_messages_fr.prop

@@ -31,7 +31,7 @@
 42S12=Index {0} non trouvé
 42S21=Duplication du nom de colonnes {0}
 42S22=Colonne {0} non trouvée
-42S32=Paramètre {0} non trouvé
+42S31=#Identical expressions should be used; expected {0}, found {1}
 57014=L'instruction a été annulée ou la session a expiré
 90000=La fonction {0} doit retourner résultat
 90001=Methode non autorisée pour une requête. Utilisez execute ou executeQuery à la place d'executeUpdate

h2/src/main/org/h2/res/_messages_ja.prop

@@ -31,7 +31,7 @@
 42S12=インデックス {0} が見つかりません
 42S21=列名 {0} が重複しています
 42S22=列 {0} が見つかりません
-42S32=設定 {0} が見つかりません
+42S31=#Identical expressions should be used; expected {0}, found {1}
 57014=ステートメントがキャンセルされたか、セッションがタイムアウトしました
 90000=関数 {0} はリザルトセットを返さなければなりません
 90001=メソッドはクエリをサポートしていません。executeUpdateのかわりに、excute、またはexecuteQueryを使用してください

h2/src/main/org/h2/res/_messages_pl.prop

@@ -31,7 +31,7 @@
 42S12=Indeks {0} nie istnieje
 42S21=Zduplikowana nazwa kolumny {0}
 42S22=Kolumna {0} nie istnieje
-42S32=Ustawienie {0} nie istnieje
+42S31=#Identical expressions should be used; expected {0}, found {1}
 57014=Kwerenda została anulowana albo sesja wygasła
 90000=Funkcja {0} musi zwrócić dane
 90001=Metoda nie jest dozwolona w kwerendzie

h2/src/main/org/h2/res/_messages_pt_br.prop

@@ -31,7 +31,7 @@
 42S12=índice {0} não foi encontrado
 42S21=Nome duplicado da coluna {0}
 42S22=Coluna {0} não foi encontrada
-42S32=Definição {0} não foi encontrada
+42S31=#Identical expressions should be used; expected {0}, found {1}
 57014=#Statement was canceled or the session timed out
 90000=Função {0} deve retornar algum resultado
 90001=O método não esta hábilitado para consulta. Use o execute ou o executeQuery em vez de executeUpdate

h2/src/main/org/h2/res/_messages_ru.prop

@@ -31,7 +31,7 @@
 42S12=Индекс {0} не найден
 42S21=Повтор имени столбца {0}
 42S22=Столбец {0} не найден
-42S32=Настройка {0} не найдена
+42S31=Должны использоваться идентичные выражения; ожидалось {0}, получено {1}
 57014=Запрос был отменен или закончилось время ожидания сессии
 90000=Функция {0} должна возвращать набор записей
 90001=Метод не разрешен для запросов. Используйте execute или executeQuery вместо executeUpdate

h2/src/main/org/h2/res/_messages_sk.prop

@@ -31,7 +31,7 @@
 42S12=Index {0} nenájdený
 42S21=Duplicitné meno stĺpca {0}
 42S22=Stĺpec {0} nenájdený
-42S32=Nastavenie {0} nenájdené
+42S31=#Identical expressions should be used; expected {0}, found {1}
 57014=Príkaz bol zrušený alebo vypršal časový limit sedenia
 90000=Funkcia {0} musí vracať výsledok (result set)
 90001=Metóda nie je povolená pre dopyt (query). Použite execute alebo executeQuery namiesto executeUpdate

h2/src/main/org/h2/res/_messages_zh_cn.prop

@@ -31,7 +31,7 @@
 42S12=找不到索引 {0}
 42S21=重复的字段： {0}
 42S22=找不到字段 {0}
-42S32=找不到设置 {0}
+42S31=#Identical expressions should be used; expected {0}, found {1}
 57014=语句已取消执行或会话已过期
 90000={0} 函数必须返回一个结果集
 90001=不允许在查询内使用的方法，使用execute 或 executeQuery 代替 executeUpdate

h2/src/test/org/h2/test/scripts/TestScript.java

@@ -137,7 +137,7 @@ public class TestScript extends TestDb {
             testScript("other/" + s + ".sql");
         }
         for (String s : new String[] { "avg", "bit-and", "bit-or", "count",
-                "group-concat", "max", "median", "min", "selectivity", "stddev-pop",
+                "group-concat", "max", "median", "min", "mode", "selectivity", "stddev-pop",
                 "stddev-samp", "sum", "var-pop", "var-samp", "array-agg" }) {
             testScript("functions/aggregate/" + s + ".sql");
         }

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

+-- Copyright 2004-2018 H2 Group. Multiple-Licensed under the MPL 2.0,
+-- and the EPL 1.0 (http://h2database.com/html/license.html).
+-- Initial Developer: H2 Group
+--
+
+CREATE TABLE TEST(V INT);
+> ok
+
+SELECT MODE(V) FROM TEST;
+>> null
+
+SELECT MODE(DISTINCT V) FROM TEST;
+> exception SYNTAX_ERROR_2
+
+INSERT INTO TEST VALUES (NULL);
+> update count: 1
+
+SELECT MODE(V) FROM TEST;
+>> null
+
+INSERT INTO TEST VALUES (1), (2), (3), (1), (2), (1);
+> update count: 6
+
+SELECT MODE(V), MODE(V) FILTER (WHERE (V > 1)), MODE(V) FILTER (WHERE (V < 0)) FROM TEST;
+> MODE(V) MODE(V) FILTER (WHERE (V > 1)) MODE(V) FILTER (WHERE (V < 0))
+> ------- ------------------------------ ------------------------------
+> 1       2                              null
+> rows: 1
+
+-- Oracle compatibility
+SELECT STATS_MODE(V) FROM TEST;
+>> 1
+
+INSERT INTO TEST VALUES (2), (3), (3);
+> update count: 3
+
+SELECT MODE(V ORDER BY V) FROM TEST;
+>> 1
+
+SELECT MODE(V ORDER BY V ASC) FROM TEST;
+>> 1
+
+SELECT MODE(V ORDER BY V DESC) FROM TEST;
+>> 3
+
+SELECT MODE(V ORDER BY V + 1) FROM TEST;
+> exception IDENTICAL_EXPRESSIONS_SHOULD_BE_USED
+
+SELECT MODE() WITHIN GROUP(ORDER BY V) FROM TEST;
+>> 1
+
+SELECT MODE() WITHIN GROUP(ORDER BY V ASC) FROM TEST;
+>> 1
+
+SELECT MODE() WITHIN GROUP(ORDER BY V DESC) FROM TEST;
+>> 3
+
+DROP TABLE TEST;
+> ok