- only expose the top 100 results in the query statistics table

- fix an occasional error in the test-case

h2/src/main/org/h2/engine/QueryStatisticsData.java

@@ -12,6 +12,7 @@ import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
+import java.util.List;
 import java.util.Map;
 
 /**
@@ -22,6 +23,8 @@ public class QueryStatisticsData {
     private static final int MAX_QUERY_ENTRIES = 100;
 
     public static final class QueryEntry {
+        public String sqlStatement;
+
         public long lastUpdateTime;
         public int count;
         public long executionTimeMin;
@@ -64,6 +67,7 @@ public class QueryStatisticsData {
         QueryEntry entry = map.get(sqlStatement);
         if (entry == null) {
             entry = new QueryEntry();
+            entry.sqlStatement = sqlStatement;
             entry.count = 1;
             entry.executionTimeMin = executionTime;
             entry.executionTimeMax = executionTime;
@@ -113,9 +117,13 @@ public class QueryStatisticsData {
         }
     }
     
-    public synchronized HashMap<String, QueryEntry> getQueryMap() {
+    public synchronized List<QueryEntry> getQueries() {
         // return a copy of the map so we don't have to worry about external synchronization
-        return new HashMap<String, QueryEntry>(map);
+        ArrayList<QueryEntry> list = new ArrayList<QueryEntry>();
+        list.addAll(map.values());
+        // only return the newest 100 entries
+        Collections.sort(list, QUERY_ENTRY_COMPARATOR);
+        return list.subList(0, Math.min(list.size(), MAX_QUERY_ENTRIES));
     }
 
     private static final Comparator<QueryEntry> QUERY_ENTRY_COMPARATOR = new Comparator<QueryEntry>() {

h2/src/main/org/h2/table/MetaTable.java

@@ -17,7 +17,6 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Locale;
-import java.util.Map;
 import org.h2.command.Command;
 import org.h2.constraint.Constraint;
 import org.h2.constraint.ConstraintCheck;
@@ -1642,12 +1641,10 @@ public class MetaTable extends Table {
         case QUERY_STATISTICS: {
             QueryStatisticsData control = database.getQueryStatisticsData();
             if (control != null) {
-                HashMap<String, QueryStatisticsData.QueryEntry> map = control.getQueryMap();
-                for (Map.Entry<String, QueryStatisticsData.QueryEntry> mapEntry : map.entrySet()) {
-                    QueryStatisticsData.QueryEntry entry = mapEntry.getValue();
+                for (QueryStatisticsData.QueryEntry entry : control.getQueries()) {
                     add(rows,
                             // SQL_STATEMENT
-                            mapEntry.getKey(),
+                            entry.sqlStatement,
                             // EXECUTION_COUNT
                             "" + entry.count,
                             // MIN_EXECUTION_TIME

h2/src/test/org/h2/test/jdbc/TestMetaData.java

@@ -1010,7 +1010,8 @@ public class TestMetaData extends TestBase {
         stat.execute("SET QUERY_STATISTICS TRUE");
         stat.execute("select * from test limit 10");
         stat.execute("select * from test limit 10");
-        rs = stat.executeQuery("select * from INFORMATION_SCHEMA.QUERY_STATISTICS");
+        // The "order by" makes the resultset more stable on windows, where the timer resolution is not that great 
+        rs = stat.executeQuery("select * from INFORMATION_SCHEMA.QUERY_STATISTICS ORDER BY EXECUTION_COUNT");
         assertTrue(rs.next());
         assertEquals("select * from test limit 10", rs.getString("SQL_STATEMENT"));
         assertEquals(2, rs.getInt("EXECUTION_COUNT"));