How to use

merge

method

in

org.apache.cassandra.db.rows.Rows

private BTree.Builder<Row> builder(int initialCapacity)
{
  return BTree.<Row>builder(metadata.comparator, initialCapacity)
        .setQuickResolver((a, b) ->
                 Rows.merge(a, b, createdAtInSec));
}

private BTree.Builder<Row> builder(int initialCapacity)
{
  return BTree.<Row>builder(metadata.comparator, initialCapacity)
        .setQuickResolver((a, b) ->
                 Rows.merge(a, b, createdAtInSec));
}

public static Row merge(Row row1, Row row2, int nowInSec)
{
  Row.Builder builder = BTreeRow.sortedBuilder();
  merge(row1, row2, builder, nowInSec);
  return builder.build();
}

public static Row merge(Row row1, Row row2, int nowInSec)
{
  Row.Builder builder = BTreeRow.sortedBuilder();
  merge(row1, row2, builder, nowInSec);
  return builder.build();
}

private BTree.Builder<Row> builder(int initialCapacity)
{
  return BTree.<Row>builder(metadata.comparator, initialCapacity)
        .setQuickResolver((a, b) ->
                 Rows.merge(a, b, createdAtInSec));
}

private BTree.Builder<Row> builder(int initialCapacity)
{
  return BTree.<Row>builder(metadata.comparator, initialCapacity)
        .setQuickResolver((a, b) ->
                 Rows.merge(a, b, createdAtInSec));
}

public static Row merge(Row row1, Row row2, int nowInSec)
{
  Row.Builder builder = BTreeRow.sortedBuilder();
  merge(row1, row2, builder, nowInSec);
  return builder.build();
}

public static Row merge(Row row1, Row row2, int nowInSec)
{
  Row.Builder builder = BTreeRow.sortedBuilder();
  merge(row1, row2, builder, nowInSec);
  return builder.build();
}

/**
 * Given an existing base row and the update that we're going to apply to this row, generate the modifications
 * to apply to MVs using the provided {@code ViewUpdateGenerator}s.
 *
 * @param existingBaseRow the base table row as it is before an update.
 * @param updateBaseRow the newly updates made to {@code existingBaseRow}.
 * @param generators the view update generators to add the new changes to.
 * @param nowInSec the current time in seconds. Used to decide if data is live or not.
 */
private static void addToViewUpdateGenerators(Row existingBaseRow, Row updateBaseRow, Collection<ViewUpdateGenerator> generators, int nowInSec)
{
  // Having existing empty is useful, it just means we'll insert a brand new entry for updateBaseRow,
  // but if we have no update at all, we shouldn't get there.
  assert !updateBaseRow.isEmpty();
  // We allow existingBaseRow to be null, which we treat the same as being empty as an small optimization
  // to avoid allocating empty row objects when we know there was nothing existing.
  Row mergedBaseRow = existingBaseRow == null ? updateBaseRow : Rows.merge(existingBaseRow, updateBaseRow, nowInSec);
  for (ViewUpdateGenerator generator : generators)
    generator.addBaseTableUpdate(existingBaseRow, mergedBaseRow);
}

/**
 * Given an existing base row and the update that we're going to apply to this row, generate the modifications
 * to apply to MVs using the provided {@code ViewUpdateGenerator}s.
 *
 * @param existingBaseRow the base table row as it is before an update.
 * @param updateBaseRow the newly updates made to {@code existingBaseRow}.
 * @param generators the view update generators to add the new changes to.
 * @param nowInSec the current time in seconds. Used to decide if data is live or not.
 */
private static void addToViewUpdateGenerators(Row existingBaseRow, Row updateBaseRow, Collection<ViewUpdateGenerator> generators, int nowInSec)
{
  // Having existing empty is useful, it just means we'll insert a brand new entry for updateBaseRow,
  // but if we have no update at all, we shouldn't get there.
  assert !updateBaseRow.isEmpty();
  // We allow existingBaseRow to be null, which we treat the same as being empty as an small optimization
  // to avoid allocating empty row objects when we know there was nothing existing.
  Row mergedBaseRow = existingBaseRow == null ? updateBaseRow : Rows.merge(existingBaseRow, updateBaseRow, nowInSec);
  for (ViewUpdateGenerator generator : generators)
    generator.addBaseTableUpdate(existingBaseRow, mergedBaseRow);
}

/**
 * Given an existing base row and the update that we're going to apply to this row, generate the modifications
 * to apply to MVs using the provided {@code ViewUpdateGenerator}s.
 *
 * @param existingBaseRow the base table row as it is before an update.
 * @param updateBaseRow the newly updates made to {@code existingBaseRow}.
 * @param generators the view update generators to add the new changes to.
 * @param nowInSec the current time in seconds. Used to decide if data is live or not.
 */
private static void addToViewUpdateGenerators(Row existingBaseRow, Row updateBaseRow, Collection<ViewUpdateGenerator> generators, int nowInSec)
{
  // Having existing empty is useful, it just means we'll insert a brand new entry for updateBaseRow,
  // but if we have no update at all, we shouldn't get there.
  assert !updateBaseRow.isEmpty();
  // We allow existingBaseRow to be null, which we treat the same as being empty as an small optimization
  // to avoid allocating empty row objects when we know there was nothing existing.
  Row mergedBaseRow = existingBaseRow == null ? updateBaseRow : Rows.merge(existingBaseRow, updateBaseRow, nowInSec);
  for (ViewUpdateGenerator generator : generators)
    generator.addBaseTableUpdate(existingBaseRow, mergedBaseRow);
}

public Row apply(Row existing, Row update)
{
  Row.Builder builder = builder(existing.clustering());
  colUpdateTimeDelta = Math.min(colUpdateTimeDelta, Rows.merge(existing, update, builder, nowInSec));
  Row reconciled = builder.build();
  indexer.onUpdated(existing, reconciled);
  dataSize += reconciled.dataSize() - existing.dataSize();
  heapSize += reconciled.unsharedHeapSizeExcludingData() - existing.unsharedHeapSizeExcludingData();
  if (inserted == null)
    inserted = new ArrayList<>();
  inserted.add(reconciled);
  return reconciled;
}

public Row apply(Row existing, Row update)
{
  Row.Builder builder = builder(existing.clustering());
  colUpdateTimeDelta = Math.min(colUpdateTimeDelta, Rows.merge(existing, update, builder, nowInSec));
  Row reconciled = builder.build();
  indexer.onUpdated(existing, reconciled);
  dataSize += reconciled.dataSize() - existing.dataSize();
  heapSize += reconciled.unsharedHeapSizeExcludingData() - existing.unsharedHeapSizeExcludingData();
  if (inserted == null)
    inserted = new ArrayList<>();
  inserted.add(reconciled);
  return reconciled;
}

public Row apply(Row existing, Row update)
{
  Row.Builder builder = builder(existing.clustering());
  colUpdateTimeDelta = Math.min(colUpdateTimeDelta, Rows.merge(existing, update, builder, nowInSec));
  Row reconciled = builder.build();
  indexer.onUpdated(existing, reconciled);
  dataSize += reconciled.dataSize() - existing.dataSize();
  heapSize += reconciled.unsharedHeapSizeExcludingData() - existing.unsharedHeapSizeExcludingData();
  if (inserted == null)
    inserted = new ArrayList<>();
  inserted.add(reconciled);
  return reconciled;
}

public Row apply(Row existing, Row update)
{
  Row.Builder builder = builder(existing.clustering());
  colUpdateTimeDelta = Math.min(colUpdateTimeDelta, Rows.merge(existing, update, builder, nowInSec));
  Row reconciled = builder.build();
  indexer.onUpdated(existing, reconciled);
  dataSize += reconciled.dataSize() - existing.dataSize();
  heapSize += reconciled.unsharedHeapSizeExcludingData() - existing.unsharedHeapSizeExcludingData();
  if (inserted == null)
    inserted = new ArrayList<>();
  inserted.add(reconciled);
  return reconciled;
}

private synchronized void build()
{
  if (isBuilt)
    return;
  Holder holder = this.holder;
  Object[] cur = holder.tree;
  Object[] add = rowBuilder.build();
  Object[] merged = BTree.<Row>merge(cur, add, metadata.comparator,
                    UpdateFunction.Simple.of((a, b) -> Rows.merge(a, b, createdAtInSec)));
  assert deletionInfo == holder.deletionInfo;
  EncodingStats newStats = EncodingStats.Collector.collect(holder.staticRow, BTree.<Row>iterator(merged), deletionInfo);
  this.holder = new Holder(holder.columns, merged, holder.deletionInfo, holder.staticRow, newStats);
  rowBuilder = null;
  isBuilt = true;
}

private synchronized void build()
{
  if (isBuilt)
    return;
  Holder holder = this.holder;
  Object[] cur = holder.tree;
  Object[] add = rowBuilder.build();
  Object[] merged = BTree.<Row>merge(cur, add, metadata.comparator,
                    UpdateFunction.Simple.of((a, b) -> Rows.merge(a, b, createdAtInSec)));
  assert deletionInfo == holder.deletionInfo;
  EncodingStats newStats = EncodingStats.Collector.collect(holder.staticRow, BTree.<Row>iterator(merged), deletionInfo);
  this.holder = new Holder(holder.columns, merged, holder.deletionInfo, holder.staticRow, newStats);
  rowBuilder = null;
  isBuilt = true;
}

private synchronized void build()
{
  if (isBuilt)
    return;
  Holder holder = this.holder;
  Object[] cur = holder.tree;
  Object[] add = rowBuilder.build();
  Object[] merged = BTree.<Row>merge(cur, add, metadata.comparator,
                    UpdateFunction.Simple.of((a, b) -> Rows.merge(a, b, createdAtInSec)));
  assert deletionInfo == holder.deletionInfo;
  EncodingStats newStats = EncodingStats.Collector.collect(holder.staticRow, BTree.<Row>iterator(merged), deletionInfo);
  this.holder = new Holder(holder.columns, merged, holder.deletionInfo, holder.staticRow, newStats);
  rowBuilder = null;
  isBuilt = true;
}

private synchronized void build()
{
  if (isBuilt)
    return;
  Holder holder = this.holder;
  Object[] cur = holder.tree;
  Object[] add = rowBuilder.build();
  Object[] merged = BTree.<Row>merge(cur, add, metadata.comparator,
                    UpdateFunction.Simple.of((a, b) -> Rows.merge(a, b, createdAtInSec)));
  assert deletionInfo == holder.deletionInfo;
  EncodingStats newStats = EncodingStats.Collector.collect(holder.staticRow, BTree.<Row>iterator(merged), deletionInfo);
  this.holder = new Holder(holder.columns, merged, holder.deletionInfo, holder.staticRow, newStats);
  rowBuilder = null;
  isBuilt = true;
}

  @Override
  public Unfiltered next()
  {
    Unfiltered next = nextToOffer != null ? nextToOffer : wrapped.next();
    if (next.isRow())
    {
      while (wrapped.hasNext())
      {
        Unfiltered peek = wrapped.next();
        if (!peek.isRow() || !next.clustering().equals(peek.clustering()))
        {
          nextToOffer = peek; // Offer peek in next call
          return next;
        }
        // Duplicate row, merge it.
        next = Rows.merge((Row) next, (Row) peek, FBUtilities.nowInSeconds());
      }
    }
    nextToOffer = null;
    return next;
  }
}