added query statistics max entries settings, SET QUERY_STATISTICS_MAX_ENTRIES

h2/src/docsrc/help/help.csv

@@ -1481,6 +1481,19 @@ Admin rights are required to execute this command, as it affects all connections
 SET QUERY_STATISTICS FALSE
 "
 
+"Commands (Other)","SET QUERY_STATISTICS_MAX_ENTRIES","
+SET QUERY_STATISTICS int
+","
+Set the maximum number of entries in query statistics meta-table.
+Default value is 100.
+
+This setting is not persistent.
+This command commits an open transaction in this connection.
+Admin rights are required to execute this command, as it affects all connections.
+","
+SET QUERY_STATISTICS_MAX_ENTRIES 500
+"
+
 "Commands (Other)","SET QUERY_TIMEOUT","
 SET QUERY_TIMEOUT int
 ","

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

@@ -393,6 +393,16 @@ public class Set extends Prepared {
             database.setQueryStatistics(value == 1);
             break;
         }
+        case SetTypes.QUERY_STATISTICS_MAX_ENTRIES: {
+            session.getUser().checkAdmin();
+            int value = getIntValue();
+            if (value < 1) {
+                throw DbException.getInvalidValueException("QUERY_STATISTICS_MAX_ENTRIES",
+                        getIntValue());
+            }
+            database.setQueryStatisticsMaxEntries(value);
+            break;
+        }
         case SetTypes.SCHEMA: {
             Schema schema = database.getSchema(stringValue);
             session.setCurrentSchema(schema);

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

@@ -218,6 +218,11 @@ public class SetTypes {
      */
     public static final int QUERY_STATISTICS = 41;
 
+    /**
+     * The type of a SET QUERY_STATISTICS_MAX_ENTRIES statement.
+     */
+    public static final int QUERY_STATISTICS_MAX_ENTRIES = 42;
+
     private static final ArrayList<String> TYPES = New.arrayList();
 
     private SetTypes() {
@@ -268,6 +273,7 @@ public class SetTypes {
         list.add(JAVA_OBJECT_SERIALIZER, "JAVA_OBJECT_SERIALIZER");
         list.add(RETENTION_TIME, "RETENTION_TIME");
         list.add(QUERY_STATISTICS, "QUERY_STATISTICS");
+        list.add(QUERY_STATISTICS_MAX_ENTRIES, "QUERY_STATISTICS_MAX_ENTRIES");
     }
 
     /**

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

@@ -505,6 +505,11 @@ public class Constants {
      */
     public static final int VIEW_INDEX_CACHE_SIZE = 64;
 
+    /**
+     * The maximum number of entries in query statistics.
+     */
+    public static final int QUERY_STATISTICS_MAX_ENTRIES = 100;
+
     private Constants() {
         // utility class
     }

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

@@ -189,6 +189,7 @@ public class Database implements DataHandler {
     private String javaObjectSerializerName;
     private volatile boolean javaObjectSerializerInitialized;
     private boolean queryStatistics;
+    private int queryStatisticsMaxEntries = Constants.QUERY_STATISTICS_MAX_ENTRIES;
     private QueryStatisticsData queryStatisticsData;
 
     public Database(ConnectionInfo ci, String cipher) {
@@ -2260,6 +2261,17 @@ public class Database implements DataHandler {
         return queryStatistics;
     }
 
+    public void setQueryStatisticsMaxEntries(int n) {
+        queryStatisticsMaxEntries = n;
+        if (queryStatisticsData != null) {
+            synchronized (this) {
+                if (queryStatisticsData != null) {
+                    queryStatisticsData.setMaxQueryEntries(queryStatisticsMaxEntries);
+                }
+            }
+        }
+    }
+
     public QueryStatisticsData getQueryStatisticsData() {
         if (!queryStatistics) {
             return null;
@@ -2267,7 +2279,7 @@ public class Database implements DataHandler {
         if (queryStatisticsData == null) {
             synchronized (this) {
                 if (queryStatisticsData == null) {
-                    queryStatisticsData = new QueryStatisticsData();
+                    queryStatisticsData = new QueryStatisticsData(queryStatisticsMaxEntries);
                 }
             }
         }

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

@@ -19,8 +19,6 @@ import java.util.Map.Entry;
  */
 public class QueryStatisticsData {
 
-    private static final int MAX_QUERY_ENTRIES = 100;
-
     private static final Comparator<QueryEntry> QUERY_ENTRY_COMPARATOR =
             new Comparator<QueryEntry>() {
         @Override
@@ -32,6 +30,16 @@ public class QueryStatisticsData {
     private final HashMap<String, QueryEntry> map =
             new HashMap<String, QueryEntry>();
 
+    private int maxQueryEntries;
+
+    public QueryStatisticsData(int maxQueryEntries) {
+        this.maxQueryEntries = maxQueryEntries;
+    }
+
+    public synchronized void setMaxQueryEntries(int maxQueryEntries) {
+        this.maxQueryEntries = maxQueryEntries;
+    }
+
     public synchronized List<QueryEntry> getQueries() {
         // return a copy of the map so we don't have to
         // worry about external synchronization
@@ -39,7 +47,7 @@ public class QueryStatisticsData {
         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));
+        return list.subList(0, Math.min(list.size(), maxQueryEntries));
     }
 
     /**
@@ -62,7 +70,7 @@ public class QueryStatisticsData {
 
         // Age-out the oldest entries if the map gets too big.
         // Test against 1.5 x max-size so we don't do this too often
-        if (map.size() > MAX_QUERY_ENTRIES * 1.5f) {
+        if (map.size() > maxQueryEntries * 1.5f) {
             // Sort the entries by age
             ArrayList<QueryEntry> list = new ArrayList<QueryEntry>();
             list.addAll(map.values());

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

@@ -56,6 +56,7 @@ public class TestMetaData extends TestBase {
         testClientInfo();
         testSessionsUncommitted();
         testQueryStatistics();
+        testQueryStatisticsLimit();
     }
 
     private void testUnwrap() throws SQLException {
@@ -1260,4 +1261,46 @@ public class TestMetaData extends TestBase {
         conn.close();
         deleteDb("metaData");
     }
+
+    private void testQueryStatisticsLimit() throws SQLException {
+        Connection conn = getConnection("metaData");
+        Statement stat = conn.createStatement();
+        stat.execute("create table test(id int primary key, name varchar) as " +
+                "select x, space(1000) from system_range(1, 2000)");
+
+        ResultSet rs = stat.executeQuery(
+                "select * from INFORMATION_SCHEMA.QUERY_STATISTICS");
+        assertFalse(rs.next());
+        rs.close();
+
+        //first, test setting the limit before activating statistics
+        int statisticsMaxEntries = 200;
+        //prevent test limit being less than or equal to default limit
+        assertTrue(statisticsMaxEntries > Constants.QUERY_STATISTICS_MAX_ENTRIES);
+        stat.execute("SET QUERY_STATISTICS_MAX_ENTRIES " + statisticsMaxEntries);
+        stat.execute("SET QUERY_STATISTICS TRUE");
+        for (int i = 0; i < statisticsMaxEntries * 2; i++) {
+            stat.execute("select * from test where id = " + i);
+        }
+        rs = stat.executeQuery("select count(*) from INFORMATION_SCHEMA.QUERY_STATISTICS");
+        assertTrue(rs.next());
+        assertEquals(statisticsMaxEntries, rs.getInt(1));
+        rs.close();
+
+        //first, test changing the limit once statistics is activated
+        int statisticsMaxEntriesNew = 50;
+        //prevent new test limit being greater than or equal to default limit
+        assertTrue(statisticsMaxEntriesNew < Constants.QUERY_STATISTICS_MAX_ENTRIES);
+        stat.execute("SET QUERY_STATISTICS_MAX_ENTRIES " + statisticsMaxEntriesNew);
+        for (int i = 0; i < statisticsMaxEntriesNew * 2; i++) {
+            stat.execute("select * from test where id = " + i);
+        }
+        rs = stat.executeQuery("select count(*) from INFORMATION_SCHEMA.QUERY_STATISTICS");
+        assertTrue(rs.next());
+        assertEquals(statisticsMaxEntriesNew, rs.getInt(1));
+        rs.close();
+
+        conn.close();
+        deleteDb("metaData");
+    }
 }