Examples with TransactionContext com.apple.foundationdb.TransactionContext used on opensource projects

Example 1 with TransactionContext

use of com.apple.foundationdb.TransactionContext in project fdb-record-layer by FoundationDB.

the class BunchedMap method compact.

/**
 * Compact the values within the map into as few keys as possible. This will scan through and re-write
 * the keys to be optimal. This feature is experimental at the moment, but it should be used to better
 * pack entries if needed.
 *
 * @param tcx database or transaction to use when compacting data
 * @param subspace subspace within which the map's data are located
 * @param keyLimit maximum number of database keys to read in a single transaction
 * @param continuation the continuation returned from a previous call or <code>null</code>
 *                     to start from the beginning of the subspace
 * @return future that will complete with a continuation that can be used to complete
 *         the compaction across multiple transactions (<code>null</code> if finished)
 */
@Nonnull
protected CompletableFuture<byte[]> compact(@Nonnull TransactionContext tcx, @Nonnull Subspace subspace, int keyLimit, @Nullable byte[] continuation) {
    return tcx.runAsync(tr -> {
        byte[] subspaceKey = subspace.getKey();
        byte[] begin = (continuation == null) ? subspaceKey : continuation;
        byte[] end = subspace.range().end;
        final AsyncIterable<KeyValue> iterable = tr.snapshot().getRange(begin, end, keyLimit);
        List<Map.Entry<K, V>> currentEntryList = new ArrayList<>(bunchSize);
        // The estimated size can be off (and will be off for many implementations of BunchedSerializer),
        // but it is just a heuristic to know when to split, so that's fine (I claim).
        AtomicInteger currentEntrySize = new AtomicInteger(0);
        AtomicInteger readKeys = new AtomicInteger(0);
        AtomicReference<byte[]> lastReadKeyBytes = new AtomicReference<>(null);
        AtomicReference<K> lastKey = new AtomicReference<>(null);
        return AsyncUtil.forEach(iterable, kv -> {
            final K boundaryKey = serializer.deserializeKey(kv.getKey(), subspaceKey.length);
            final List<Map.Entry<K, V>> entriesFromKey = serializer.deserializeEntries(boundaryKey, kv.getValue());
            readKeys.incrementAndGet();
            if (entriesFromKey.size() >= bunchSize && currentEntryList.isEmpty()) {
                // Nothing can be done. Just move on.
                lastReadKeyBytes.set(null);
                return;
            }
            if (lastReadKeyBytes.get() == null) {
                lastReadKeyBytes.set(kv.getKey());
            }
            final byte[] endKeyBytes = ByteArrayUtil.join(subspaceKey, serializer.serializeKey(entriesFromKey.get(entriesFromKey.size() - 1).getKey()), ZERO_ARRAY);
            tr.addReadConflictRange(lastReadKeyBytes.get(), endKeyBytes);
            tr.addWriteConflictRange(lastReadKeyBytes.get(), kv.getKey());
            lastReadKeyBytes.set(endKeyBytes);
            tr.clear(kv.getKey());
            instrumentDelete(kv.getKey(), kv.getValue());
            for (Map.Entry<K, V> entry : entriesFromKey) {
                byte[] serializedEntry = serializer.serializeEntry(entry);
                if (currentEntrySize.get() + serializedEntry.length > MAX_VALUE_SIZE && !currentEntryList.isEmpty()) {
                    flushEntryList(tr, subspaceKey, currentEntryList, lastKey);
                    currentEntrySize.set(0);
                }
                currentEntryList.add(entry);
                currentEntrySize.addAndGet(serializedEntry.length);
                if (currentEntryList.size() == bunchSize) {
                    flushEntryList(tr, subspaceKey, currentEntryList, lastKey);
                    currentEntrySize.set(0);
                }
            }
        }, tr.getExecutor()).thenApply(vignore -> {
            if (!currentEntryList.isEmpty()) {
                flushEntryList(tr, subspaceKey, currentEntryList, lastKey);
            }
            // Return a valid continuation if there might be more keys
            if (lastKey.get() != null && keyLimit != ReadTransaction.ROW_LIMIT_UNLIMITED && readKeys.get() == keyLimit) {
                return ByteArrayUtil.join(subspaceKey, serializer.serializeKey(lastKey.get()), ZERO_ARRAY);
            } else {
                return null;
            }
        });
    });
}