Function loadSnapshotFile

fdbclient/BlobGranuleFiles.cpp:773–839

TODO: use redwood prefix trick to optimize cpu comparison

// TODO: use redwood prefix trick to optimize cpu comparison
static Standalone<VectorRef<ParsedDeltaBoundaryRef>> loadSnapshotFile(
    const Standalone<StringRef>& fileName,
    const StringRef& snapshotData,
    const KeyRangeRef& keyRange,
    Optional<BlobGranuleCipherKeysCtx> cipherKeysCtx) {
	Standalone<VectorRef<ParsedDeltaBoundaryRef>> results;

	if (BG_ENCRYPT_COMPRESS_DEBUG) {
		TraceEvent(SevDebug, "LoadChunkedSnapshot")
		    .detail("FileName", fileName.toString())
		    .detail("RangeBegin", keyRange.begin.printable())
		    .detail("RangeEnd", keyRange.end.printable())
		    .detail("Encrypted", cipherKeysCtx.present());
	}

	Standalone<IndexedBlobGranuleFile> file = IndexedBlobGranuleFile::fromFileBytes(snapshotData, cipherKeysCtx);

	ASSERT(file.fileType == SNAPSHOT_FILE_TYPE);
	ASSERT(file.chunkStartOffset > 0);

	// empty snapshot file
	if (file.indexBlockRef.block.children.empty()) {
		return results;
	}

	ASSERT(file.indexBlockRef.block.children.size() >= 2);

	// find range of blocks needed to read
	ChildBlockPointerRef* currentBlock = file.findStartBlock(keyRange.begin);

	if (currentBlock == (file.indexBlockRef.block.children.end() - 1) || keyRange.end <= currentBlock->key) {
		return results;
	}

	bool lastBlock = false;

	// FIXME: shared prefix for key comparison
	while (!lastBlock) {
		auto nextBlock = currentBlock;
		nextBlock++;
		lastBlock = (nextBlock == (file.indexBlockRef.block.children.end() - 1)) || (keyRange.end <= nextBlock->key);
		Standalone<GranuleSnapshot> dataBlock =
		    file.getChild<GranuleSnapshot>(currentBlock, cipherKeysCtx, file.chunkStartOffset);
		ASSERT(!dataBlock.empty());
		ASSERT(currentBlock->key == dataBlock.front().key);

		bool anyRows = false;
		for (auto& entry : dataBlock) {
			if (!results.empty() && !lastBlock) {
				// no key comparisons needed
				results.emplace_back(results.arena(), entry);
				anyRows = true;
			} else if ((!results.empty() || entry.key >= keyRange.begin) && (!lastBlock || entry.key < keyRange.end)) {
				results.emplace_back(results.arena(), entry);
				anyRows = true;
			} else if (!results.empty() && lastBlock) {
				break;
			}