Replace TreeSet with PriorityQueue in MVSecondaryIndex re-build

h2/src/main/org/h2/mvstore/db/MVSecondaryIndex.java

@@ -10,7 +10,8 @@ import java.util.Collections;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
-import java.util.TreeSet;
+import java.util.PriorityQueue;
+import java.util.Queue;
 import org.h2.api.ErrorCode;
 import org.h2.engine.Database;
 import org.h2.engine.Session;
@@ -37,16 +38,14 @@ import org.h2.value.ValueNull;
 /**
  * A table stored in a MVStore.
  */
-public class MVSecondaryIndex extends BaseIndex implements MVIndex {
+public final class MVSecondaryIndex extends BaseIndex implements MVIndex {
 
     /**
      * The multi-value table.
      */
-    final MVTable mvTable;
-
-    private final int keyColumns;
-    private final String mapName;
-    private TransactionMap<Value, Value> dataMap;
+    private final MVTable                     mvTable;
+    private final int                         keyColumns;
+    private final TransactionMap<Value,Value> dataMap;
 
     public MVSecondaryIndex(Database db, MVTable table, int id, String indexName,
                 IndexColumn[] columns, IndexType indexType) {
@@ -58,7 +57,7 @@ public class MVSecondaryIndex extends BaseIndex implements MVIndex {
         // always store the row key in the map key,
         // even for unique indexes, as some of the index columns could be null
         keyColumns = columns.length + 1;
-        mapName = "index." + getId();
+        String mapName = "index." + getId();
         int[] sortTypes = new int[keyColumns];
         for (int i = 0; i < columns.length; i++) {
             sortTypes[i] = columns[i].sortType;
@@ -77,84 +76,91 @@ public class MVSecondaryIndex extends BaseIndex implements MVIndex {
 
     @Override
     public void addRowsToBuffer(List<Row> rows, String bufferName) {
-        MVMap<Value, Value> map = openMap(bufferName);
+        MVMap<ValueArray, Value> map = openMap(bufferName);
         for (Row row : rows) {
             ValueArray key = convertToKey(row);
             map.put(key, ValueNull.INSTANCE);
         }
     }
 
-    @Override
-    public void addBufferedRows(List<String> bufferNames) {
-        ArrayList<String> mapNames = New.arrayList(bufferNames);
-        final CompareMode compareMode = database.getCompareMode();
-        /**
-         * A source of values.
-         */
-        class Source implements Comparable<Source> {
-            Value value;
-            Iterator<Value> next;
-            int sourceId;
+    private static final class Source {
+        private final Iterator<ValueArray> iterator;
+        private       ValueArray           currentRowData;
+
+        public Source(Iterator<ValueArray> iterator) {
+            this.iterator = iterator;
+            this.currentRowData = iterator.next();
+        }
+
+        public boolean hasNext() {
+            boolean result = iterator.hasNext();
+            if(result) {
+                currentRowData = iterator.next();
+            }
+            return result;
+        }
+
+        public ValueArray next() {
+            return currentRowData;
+        }
+
+        public static final class Comparator implements java.util.Comparator<Source> {
+            private final CompareMode compareMode;
+
+            public Comparator(CompareMode compareMode) {
+                this.compareMode = compareMode;
+            }
+
             @Override
-            public int compareTo(Source o) {
-                int comp = value.compareTo(o.value, compareMode);
-                if (comp == 0) {
-                    comp = sourceId - o.sourceId;
-                }
-                return comp;
+            public int compare(Source one, Source two) {
+                return one.currentRowData.compareTo(two.currentRowData, compareMode);
             }
         }
-        TreeSet<Source> sources = new TreeSet<>();
-        for (int i = 0; i < bufferNames.size(); i++) {
-            MVMap<Value, Value> map = openMap(bufferNames.get(i));
-            Iterator<Value> it = map.keyIterator(null);
-            if (it.hasNext()) {
-                Source s = new Source();
-                s.value = it.next();
-                s.next = it;
-                s.sourceId = i;
-                sources.add(s);
+    }
+
+    @Override
+    public void addBufferedRows(List<String> bufferNames) {
+        ArrayList<String> mapNames = New.arrayList(bufferNames);
+        CompareMode compareMode = database.getCompareMode();
+        int buffersCount = bufferNames.size();
+        Queue<Source> queue = new PriorityQueue<>(buffersCount, new Source.Comparator(compareMode));
+        for (String bufferName : bufferNames) {
+            Iterator<ValueArray> iter = openMap(bufferName).keyIterator(null);
+            if (iter.hasNext()) {
+                queue.add(new Source(iter));
             }
         }
+
         try {
-            while (true) {
-                Source s = sources.first();
-                Value v = s.value;
+            while (!queue.isEmpty()) {
+                Source s = queue.remove();
+                ValueArray rowData = s.next();
 
                 if (indexType.isUnique()) {
-                    Value[] array = ((ValueArray) v).getList();
+                    Value[] array = rowData.getList();
                     // don't change the original value
                     array = array.clone();
                     array[keyColumns - 1] = ValueLong.get(Long.MIN_VALUE);
                     ValueArray unique = ValueArray.get(array);
-                    SearchRow row = convertToSearchRow((ValueArray) v);
+                    SearchRow row = convertToSearchRow(rowData);
                     checkUnique(row, dataMap, unique);
                 }
 
-                dataMap.putCommitted(v, ValueNull.INSTANCE);
+                dataMap.putCommitted(rowData, ValueNull.INSTANCE);
 
-                Iterator<Value> it = s.next;
-                if (!it.hasNext()) {
-                    sources.remove(s);
-                    if (sources.size() == 0) {
-                        break;
-                    }
-                } else {
-                    Value nextValue = it.next();
-                    sources.remove(s);
-                    s.value = nextValue;
-                    sources.add(s);
+                if (s.hasNext()) {
+                    queue.offer(s);
                 }
             }
         } finally {
             for (String tempMapName : mapNames) {
-                MVMap<Value, Value> map = openMap(tempMapName);
+                MVMap<ValueArray, Value> map = openMap(tempMapName);
                 map.getStore().removeMap(map);
             }
         }
     }
 
-    private MVMap<Value, Value> openMap(String mapName) {
+    private MVMap<ValueArray, Value> openMap(String mapName) {
         int[] sortTypes = new int[keyColumns];
         for (int i = 0; i < indexColumns.length; i++) {
             sortTypes[i] = indexColumns[i].sortType;
@@ -163,9 +169,9 @@ public class MVSecondaryIndex extends BaseIndex implements MVIndex {
         ValueDataType keyType = new ValueDataType(
                 database.getCompareMode(), database, sortTypes);
         ValueDataType valueType = new ValueDataType(null, null, null);
-        MVMap.Builder<Value, Value> builder =
-                new MVMap.Builder<Value, Value>().keyType(keyType).valueType(valueType);
-        MVMap<Value, Value> map = database.getMvStore().
+        MVMap.Builder<ValueArray, Value> builder =
+                new MVMap.Builder<ValueArray, Value>().keyType(keyType).valueType(valueType);
+        MVMap<ValueArray, Value> map = database.getMvStore().
                 getStore().openMap(mapName, builder);
         if (!keyType.equals(map.getKeyType())) {
             throw DbException.throwInternalError("Incompatible key type");
@@ -332,7 +338,7 @@ public class MVSecondaryIndex extends BaseIndex implements MVIndex {
      * @param key the index key
      * @return the row
      */
-    SearchRow convertToSearchRow(ValueArray key) {
+    private SearchRow convertToSearchRow(ValueArray key) {
         Value[] array = key.getList();
         SearchRow searchRow = mvTable.getTemplateRow();
         searchRow.setKey((array[array.length - 1]).getLong());
@@ -455,7 +461,7 @@ public class MVSecondaryIndex extends BaseIndex implements MVIndex {
      * @param session the session
      * @return the map
      */
-    TransactionMap<Value, Value> getMap(Session session) {
+    private TransactionMap<Value, Value> getMap(Session session) {
         if (session == null) {
             return dataMap;
         }
@@ -466,7 +472,7 @@ public class MVSecondaryIndex extends BaseIndex implements MVIndex {
     /**
      * A cursor.
      */
-    class MVStoreCursor implements Cursor {
+    final class MVStoreCursor implements Cursor {
 
         private final Session session;
         private final Iterator<Value> it;
@@ -475,7 +481,7 @@ public class MVSecondaryIndex extends BaseIndex implements MVIndex {
         private SearchRow searchRow;
         private Row row;
 
-        public MVStoreCursor(Session session, Iterator<Value> it, SearchRow last) {
+        private MVStoreCursor(Session session, Iterator<Value> it, SearchRow last) {
             this.session = session;
             this.it = it;
             this.last = last;