refactoring after review

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

@@ -1081,10 +1081,6 @@ public class TableFilter implements ColumnResolver {
         return session;
     }
     
-    private static boolean isRow(Object x) {
-        return x instanceof Row;
-    }
-    
     /**
      * A visitor for table filters.
      */
@@ -1145,7 +1141,11 @@ public class TableFilter implements ColumnResolver {
         private Value getValue(JoinFilter filter, Column column) {
             Object x = current.row[filter.id];
             assert x != null;
-            Row row = isRow(x) ? (Row) x : ((Cursor) x).get();
+            Row row = current.isRow(filter.id) ? (Row) x : ((Cursor) x).get();
+            int columnId = column.getColumnId();
+            if (columnId == -1) {
+                return ValueLong.get(row.getKey());
+            }
             Value value = row.getValue(column.getColumnId());
             if (value == null) {
                 throw DbException.throwInternalError("value is null: " + column + " " + row);
@@ -1154,6 +1154,11 @@ public class TableFilter implements ColumnResolver {
         }
         
         private void start() {
+            if (filtersCount > 32) {
+                // This is because we store state in a 64 bit field, 2 bits per joined table.
+                throw DbException.getUnsupportedException("To many tables in join (at most 32 supported).");
+            }
+
             // fill filters
             filters = new JoinFilter[filtersCount];
             JoinFilter jf = top;
@@ -1164,9 +1169,12 @@ public class TableFilter implements ColumnResolver {
             // initialize current row
             current = new JoinRow(new Object[filtersCount]);
             current.row[top.id] = top.filter.cursor;
+            current.incrementState(top.id, 2);
+            assert current.isCursor(top.id);
+
             // initialize top cursor
             top.filter.cursor.find(top.filter.session, top.filter.indexConditions);
-            
+
             // we need fake first row because batchedNext always will move to the next row
             JoinRow fake = new JoinRow(null);
             fake.next = current;
@@ -1202,7 +1210,7 @@ public class TableFilter implements ColumnResolver {
             }
         }
         
-        private Cursor get(Future<Cursor> f) {
+        private static Cursor get(Future<Cursor> f) {
             try {
                 return f.get();
             } catch (Exception e) {
@@ -1272,12 +1280,12 @@ public class TableFilter implements ColumnResolver {
                 } else {
                     // here we don't care if the current was dropped
                     current = current.next;
-                    assert !isRow(current.row[jfId]);
+                    assert !current.isRow(jfId);
                     while (current.row[jfId] == null) {
                         assert jfId != top.id;
                         // need to go left and fetch more search rows
                         jfId--;
-                        assert !isRow(current.row[jfId]);
+                        assert !current.isRow(jfId);
                     }
                 }
             }
@@ -1285,32 +1293,37 @@ public class TableFilter implements ColumnResolver {
         
         @SuppressWarnings("unchecked")
         private void fetchCurrent(final int jfId) {
-            assert current.prev == null || isRow(current.prev.row[jfId]) : "prev must be already fetched";
-            assert jfId == 0 || isRow(current.row[jfId - 1]) : "left must be already fetched";
-            
+            assert current.prev == null || current.prev.isRow(jfId) : "prev must be already fetched";
+            assert jfId == 0 || current.isRow(jfId - 1) : "left must be already fetched";
+
+            assert !current.isRow(jfId) : "double fetching";
+
             Object x = current.row[jfId];
             assert x != null : "x null";
-            assert !isRow(x) : "double fetching";
-            
+
             final JoinFilter jf = filters[jfId];
             // in case of outer join we don't have any future around empty cursor
             boolean newCursor = x == EMPTY_CURSOR;
 
-            if (!newCursor && x instanceof Future) {
+            if (!newCursor && current.isFuture(jfId)) {
                 // get cursor from a future
                 current.row[jfId] = x = get((Future<Cursor>) x);
+                current.incrementState(jfId, 1);
+                assert current.isCursor(jfId);
                 newCursor = true;
             }
-            
+
             Cursor c = (Cursor) x;
             assert c != null;
             JoinFilter join = jf.join;
-            
+
             for (;;) {
                 if (c == null || !c.next()) {
                     if (newCursor && jf.isOuterJoin()) {
                         // replace cursor with null-row
                         current.row[jfId] = jf.getNullRow();
+                        current.incrementState(jfId, 1);
+                        assert current.isRow(jfId);
                         c = null;
                         newCursor = false;
                     } else {
@@ -1336,14 +1349,19 @@ public class TableFilter implements ColumnResolver {
                     current = current.copyBehind(jf.id);
                     // get current row from cursor
                     current.row[jfId] = c.get();
+                    current.incrementState(jfId, 1);
+                    assert current.isRow(jfId);
                 }
                 if (joinEmpty) {
+                    assert current.row[join.id] == null;
                     current.row[join.id] = EMPTY_CURSOR;
+                    current.incrementState(join.id, 2);
+                    assert current.isCursor(join.id);
                 }
                 return;
             }
         }
-        
+
         @Override
         public String toString() {
             return "JoinBatch->\nprev->" + (current == null ? null : current.prev) +
@@ -1438,7 +1456,7 @@ public class TableFilter implements ColumnResolver {
                 // go backwards and assign futures
                 ListIterator<Future<Cursor>> iter = result.listIterator(result.size());
                 for (;;) {
-                    assert isRow(current.row[id - 1]);
+                    assert current.isRow(id - 1);
                     if (current.row[id] == EMPTY_CURSOR) {
                         // outer join support - skip row with existing empty cursor
                         current = current.prev;
@@ -1446,7 +1464,15 @@ public class TableFilter implements ColumnResolver {
                     }
                     assert current.row[id] == null;
                     Future<Cursor> future = iter.previous();
-                    current.row[id] = future == null ? EMPTY_CURSOR : future;
+                    if (future == null) {
+                        current.row[id] = EMPTY_CURSOR;
+                        current.incrementState(id, 2);
+                        assert current.isCursor(id);
+                    } else {
+                        current.row[id] = future;
+                        current.incrementState(id, 1);
+                        assert current.isFuture(id);
+                    }
                     if (current.prev == null || !iter.hasPrevious()) {
                         break;
                     } 
@@ -1458,9 +1484,9 @@ public class TableFilter implements ColumnResolver {
             while (current.prev != null && current.prev.row[id] == EMPTY_CURSOR) {
                 current = current.prev;
             }
-            assert current.prev == null || isRow(current.prev.row[id]);
+            assert current.prev == null || current.prev.isRow(id);
             assert current.row[id] != null;
-            assert !isRow(current.row[id]);
+            assert !current.isRow(id);
             
             // the last updated row
             return current;
@@ -1476,6 +1502,12 @@ public class TableFilter implements ColumnResolver {
      * Linked row in batched join.
      */
     private static final class JoinRow {
+        private static final long S_FUTURE = 1;
+        private static final long S_CURSOR = 2;
+        private static final long S_ROW = 3;
+
+        private static final long S_MASK = 3;
+
         /**
          * May contain one of the following:
          * <br/>- {@code null}: means that we need to get future cursor for this row
@@ -1484,19 +1516,54 @@ public class TableFilter implements ColumnResolver {
          * <br/>- {@link Row}: the {@link Row} is already fetched and is ready to be used
          */
         Object[] row;
-        
+        long state;
+
         JoinRow prev;
         JoinRow next;
-        
+
         /**
          * @param row Row.
          */
         private JoinRow(Object[] row) {
             this.row = row;
         }
-        
+
+        /**
+         * @param joinFilterId Join filter id.
+         * @return Row state.
+         */
+        private long getState(int joinFilterId) {
+            return (state >>> (joinFilterId << 1)) & S_MASK;
+        }
+
+        /**
+         * Allows to do a state transition in the following order:
+         * 0. Slot contains {@code null} (no constant because simple null check is sufficient).
+         * 1. Slot contains {@link Future} ({@link #S_FUTURE}).
+         * 2. Slot contains {@link Cursor} ({@link #S_CURSOR}).
+         * 3. Slot contains {@link Row} ({@link #S_ROW}).
+         *
+         * @param joinFilterId {@link JoinRow} filter id.
+         * @param i Increment by this number of moves.
+         */
+        private void incrementState(int joinFilterId, long i) {
+            state += i << (joinFilterId << 1);
+        }
+
+        private boolean isRow(int joinFilterId) {
+            return getState(joinFilterId) == S_ROW;
+        }
+
+        private boolean isFuture(int joinFilterId) {
+            return getState(joinFilterId) == S_FUTURE;
+        }
+
+        private boolean isCursor(int joinFilterId) {
+            return getState(joinFilterId) == S_CURSOR;
+        }
+
         private boolean isComplete() {
-            return isRow(row[row.length - 1]);
+            return isRow(row.length - 1);
         }
 
         private boolean isDropped() {
@@ -1513,8 +1580,14 @@ public class TableFilter implements ColumnResolver {
             row = null;
         }
         
+        /**
+         * Copy this JoinRow behind itself in linked list of all in progress rows.
+         *
+         * @param jfId The last fetched filter id.
+         * @return The copy.
+         */
         private JoinRow copyBehind(int jfId) {
-            assert row[jfId] instanceof Cursor;
+            assert isCursor(jfId);
             assert jfId + 1 == row.length || row[jfId + 1] == null;
             
             Object[] r = new Object[row.length];
@@ -1522,6 +1595,7 @@ public class TableFilter implements ColumnResolver {
                 System.arraycopy(row, 0, r, 0, jfId);
             }
             JoinRow copy = new JoinRow(r);
+            copy.state = state;
             
             if (prev != null) {
                 copy.prev = prev;