Examples with ChainedCursor com.apple.foundationdb.record.cursors.ChainedCursor used on opensource projects

Example 1 with ChainedCursor

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

the class KeySpaceDirectory method listSubdirectoryAsync.

@Nonnull
// SonarQube doesn't realize that the cursor is wrapped and returned
@SuppressWarnings("squid:S2095")
protected RecordCursor<ResolvedKeySpacePath> listSubdirectoryAsync(@Nullable KeySpacePath listFrom, @Nonnull FDBRecordContext context, @Nonnull String subdirName, @Nullable ValueRange<?> valueRange, @Nullable byte[] continuation, @Nonnull ScanProperties scanProperties) {
    if (listFrom != null && listFrom.getDirectory() != this) {
        throw new RecordCoreException("Provided path does not belong to this directory").addLogInfo("path", listFrom, "directory", this.getName());
    }
    final KeySpaceDirectory subdir = getSubdirectory(subdirName);
    final CompletableFuture<ResolvedKeySpacePath> resolvedFromFuture = listFrom == null ? CompletableFuture.completedFuture(null) : listFrom.toResolvedPathAsync(context);
    // The chained cursor cannot implement reverse scan, so we implement it by having the
    // inner key value cursor do the reversing but telling the chained cursor we are moving
    // forward.
    final ScanProperties chainedCursorScanProperties;
    if (scanProperties.isReverse()) {
        chainedCursorScanProperties = scanProperties.setReverse(false);
    } else {
        chainedCursorScanProperties = scanProperties;
    }
    // For the read of the individual row keys, we only want to read a single key. In addition,
    // the ChainedCursor is going to do counting of our reads to apply any limits that were specified
    // on the ScanProperties.  We don't want the inner KeyValueCursor in nextTuple() to ALSO count those
    // same reads so we clear out its limits.
    final ScanProperties keyReadScanProperties = scanProperties.with(props -> props.clearState().setReturnedRowLimit(1));
    return new LazyCursor<>(resolvedFromFuture.thenCompose(resolvedFrom -> {
        final Subspace subspace = resolvedFrom == null ? new Subspace() : resolvedFrom.toSubspace();
        return subdir.getValueRange(context, valueRange, subspace).thenApply(range -> {
            final RecordCursor<Tuple> cursor = new ChainedCursor<>(context, lastKey -> nextTuple(context, subspace, range, lastKey, keyReadScanProperties), Tuple::pack, Tuple::fromBytes, continuation, chainedCursorScanProperties);
            return cursor.mapPipelined(tuple -> {
                final Tuple key = Tuple.fromList(tuple.getItems());
                return findChildForKey(context, resolvedFrom, key, 1, 0);
            }, 1);
        });
    }), context.getExecutor());
}