CASSANDRA-19355: Refactort CommandsForRange to work based off disk state rather than in-memory state

accord-core/src/main/java/accord/local/CommandsForKey.java

@@ -1698,7 +1698,6 @@ public boolean equals(Object o)
         if (o == null || getClass() != o.getClass()) return false;
         CommandsForKey that = (CommandsForKey) o;
         return Objects.equals(key, that.key)
-               && Objects.equals(redundantBefore, that.redundantBefore)
                && Arrays.equals(txns, that.txns);
     }
 

accord-core/src/main/java/accord/utils/CheckpointIntervalArray.java

@@ -0,0 +1,222 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package accord.utils;
+
+import java.util.Arrays;
+
+import accord.utils.CheckpointIntervalArrayBuilder.Accessor;
+import net.nicoulaj.compilecommand.annotations.Inline;
+
+import static accord.utils.SortedArrays.Search.CEIL;
+
+public class CheckpointIntervalArray<Ranges, Range, Key>
+{
+    // scan distance can be kept very small as we guarantee to use at most linear extra space even with a scan distance of zero
+    static final int MAX_SCAN_DISTANCE = 255;
+    protected static final int BIT30 = 0x40000000;
+    protected static final int BIT29 = 0x20000000;
+
+    final Ranges ranges;
+
+    /**
+     * The lower bound for each checkpoint.
+     * The checkpoint {@code i} applies to all ranges (incl) starting from {@code lowerBounds[i]},
+     * but before (excl) {@code lowerBounds[i+1]}.
+     */
+    final int[] lowerBounds;
+
+    /**
+     * Logically one entry per checkpoint, mapping {@link #lowerBounds} to {@link #checkpointLists},
+     * however we also encode an additional byte per entry representing the scan distance for the
+     * ranges handled by this checkpoint. These are grouped into an integer per four mappings, i.e.
+     * we encode batches of five ints, with the first int containing the four scan distances for the
+     * next four checkpoints, and the following four ints containing the respective offsets into
+     * {@link #checkpointLists}.
+     * <p>
+     * [0.........32b.........64b.........96b........128b........160b........192b]
+     * [ d1 d2 d3 d4  mapping1    mapping2   mapping3    mapping4    d5 d6 d7 d8 ]
+     */
+    final int[] headers;
+
+    /**
+     * A list of indexes in {@link #ranges} contained by each checkpoint; checkpoints are
+     * mapped from {@link #lowerBounds} by {@link #headers}.
+     * <p>
+     * Entries are sorted in descending order by the end of the range they cover, so that
+     * a search of this collection my terminate as soon as it encounters a range that does
+     * not cover the item we are searching for.
+     * <p>
+     * This collection may contain negative values, in which case these point to other
+     * checkpoints, whose <i>direct</i> contents (i.e. the positive values of) we may
+     * search.
+     * <ul> if negative, points to an earlier checkpoint, and:
+     *   <li>if the 30th bit is set, the low 20 bits point to checkpointsList,
+     *       and the 9 bits in-between provide the length of the range</li>
+     *   <li>otherwise, if the 29th bit is set, the lower 29 bits points to checkpointsList,
+     *       and can be iterated safely without an endIndex</li>
+     *   <li>otherwise, the low 29 bits provide the length of the run, and the low 31 bits
+     *       of the following entry (which will also be negative) provide a pointer to
+     *       checkpointsList</li>
+     * </ul>
+     */
+    final int[] checkpointLists;
+
+    public final int maxScanAndCheckpointMatches;
+    private final Accessor<Ranges, Range, Key> accessor;
+
+    public CheckpointIntervalArray(Accessor<Ranges, Range, Key> accessor, Ranges ranges,
+                                   int[] lowerBounds, int[] headers, int[] checkpointLists, int maxScanAndCheckpointMatches)
+    {
+        this.accessor = accessor;
+        this.ranges = ranges;
+        this.lowerBounds = lowerBounds;
+        this.headers = headers;
+        this.checkpointLists = checkpointLists;
+        this.maxScanAndCheckpointMatches = maxScanAndCheckpointMatches;
+    }
+
+    @Inline
+    public <P1, P2, P3, P4> int forEach(Range range, IndexedQuadConsumer<P1, P2, P3, P4> forEachScanOrCheckpoint, IndexedRangeQuadConsumer<P1, P2, P3, P4> forEachRange, P1 p1, P2 p2, P3 p3, P4 p4, int minIndex)
+    {
+        return forEach(accessor.start(range), accessor.end(range), forEachScanOrCheckpoint, forEachRange, p1, p2, p3, p4, minIndex);
+    }
+
+    public <P1, P2, P3, P4> int forEach(Key startKey, Key endKey, IndexedQuadConsumer<P1, P2, P3, P4> forEachScanOrCheckpoint, IndexedRangeQuadConsumer<P1, P2, P3, P4> forEachRange, P1 p1, P2 p2, P3 p3, P4 p4, int minIndex)
+    {
+        if (accessor.size(ranges) == 0 || minIndex == accessor.size(ranges))
+            return minIndex;
+
+        var c = accessor.keyComparator();
+        int end = accessor.binarySearch(ranges, minIndex, accessor.size(ranges), endKey, (a, b) -> c.compare(a, accessor.start(b)), CEIL);
+        if (end < 0) end = -1 - end;
+        if (end <= minIndex) return minIndex;
+
+        int floor = accessor.binarySearch(ranges, minIndex, accessor.size(ranges), startKey, (a, b) -> c.compare(a, accessor.start(b)), CEIL);
+        int start = floor;
+        if (floor < 0)
+        {
+            // if there's no precise match on start, step backwards;
+            // if this range does not overlap us, step forwards again for start
+            // but retain the floor index for performing scan and checkpoint searches from
+            // as this contains all ranges that might overlap us (whereas those that end
+            // after us but before the next range's start would be missed by the next range index)
+            start = floor = -2 - floor;
+            if (start < 0)
+                start = floor = 0;
+            else if (c.compare(accessor.end(ranges, start), startKey) <= 0)
+                ++start;
+        }
+
+        // Since endInclusive() != startInclusive(), so no need to adjust start/end comparisons
+        return forEach(start, end, floor, startKey, 0, forEachScanOrCheckpoint, forEachRange, p1, p2, p3, p4, minIndex);
+    }
+
+    @Inline
+    protected <P1, P2, P3, P4> int forEach(int start, int end, int floor, Key startBound, int cmpStartBoundWithEnd,
+                                           IndexedQuadConsumer<P1, P2, P3, P4> forEachScanOrCheckpoint, IndexedRangeQuadConsumer<P1, P2, P3, P4> forEachRange,
+                                           P1 p1, P2 p2, P3 p3, P4 p4, int minIndex)
+    {
+        if (start < minIndex) start = minIndex;
+
+        // find the checkpoint array, so we know how far to step back
+        int checkpoint = Arrays.binarySearch(lowerBounds, floor);
+        if (checkpoint < 0) checkpoint = -2 - checkpoint;
+        if (checkpoint < 0) return end;
+
+        int headerBaseIndex = (checkpoint / 4) * 5;
+        int headerSubIndex = checkpoint & 3;
+        int headerListIndex = headerBaseIndex + 1 + headerSubIndex;
+
+        int scanDistance = (headers[headerBaseIndex] >>> (8 * headerSubIndex)) & 0xff;
+        int checkpointStart = headers[headerListIndex];
+        int checkpointEnd = headers[headerListIndex + (headerSubIndex + 5)/4]; // skip the next header
+
+        if (scanDistance == MAX_SCAN_DISTANCE)
+        {
+            scanDistance = -checkpointLists[checkpointStart++];
+            Invariants.checkState(scanDistance >= MAX_SCAN_DISTANCE);
+        }
+
+        // NOTE: we visit in approximately ascending order, and this is a requirement for correctness of RangeDeps builders
+        //       Only the checkpoint is visited in uncertain order, but it is visited entirely, before the scan matches
+        //       and the range matches
+        int minScanIndex = Math.max(floor - scanDistance, minIndex);
+        var c = accessor.keyComparator();
+        for (int i = checkpointStart; i < checkpointEnd ; ++i)
+        {
+            int ri = checkpointLists[i];
+            if (ri < 0)
+            {
+                int subStart, subEnd;
+                if ((ri & BIT30) != 0)
+                {
+                    subStart = ri & 0xfffff;
+                    subEnd = subStart + ((ri >>> 20) & 0x1ff);
+                }
+                else if ((ri & BIT29) != 0)
+                {
+                    subStart = ri & 0x1fffffff;
+                    subEnd = Integer.MAX_VALUE;
+                }
+                else
+                {
+                    int length = ri & 0x1fffffff;
+                    subStart = checkpointLists[++i];
+                    subEnd = subStart + length;
+                }
+
+                for (int j = subStart ; j < subEnd ; ++j)
+                {
+                    ri = checkpointLists[j];
+                    if (ri < 0)
+                        continue;
+
+                    if (c.compare(accessor.end(ranges, ri), startBound) <= cmpStartBoundWithEnd)
+                        break;
+
+                    if (ri >= minIndex && ri < minScanIndex)
+                        forEachScanOrCheckpoint.accept(p1, p2, p3, p4, ri);
+                }
+            }
+            else
+            {
+                // if startBound is key, we cannot be equal to it;
+                // if startBound is a Range start, we also cannot be equal to it due to the requirement that
+                // endInclusive() != startInclusive(), so equality really means inequality
+                if (c.compare(accessor.end(ranges, ri), startBound) <= cmpStartBoundWithEnd)
+                    break;
+
+                if (ri >= minIndex && ri < minScanIndex)
+                    forEachScanOrCheckpoint.accept(p1, p2, p3, p4, ri);
+            }
+        }
+
+        for (int i = minScanIndex; i < floor ; ++i)
+        {
+            if (c.compare(accessor.end(ranges, i), startBound) > cmpStartBoundWithEnd)
+                forEachScanOrCheckpoint.accept(p1, p2, p3, p4, i);
+        }
+
+        if (start == end)
+            return end;
+
+        forEachRange.accept(p1, p2, p3, p4, start, end);
+        return end;
+    }
+}