void Table::ReadMeta(const Footer& footer) { if (rep_->options.filter_policy == NULL) { return; // Do not need any metadata } // TODO(sanjay): Skip this if footer.metaindex_handle() size indicates // it is an empty block. ReadOptions opt; if (rep_->options.paranoid_checks) { opt.verify_checksums = true; } BlockContents contents; if (!ReadBlock(rep_->file, opt, footer.metaindex_handle(), &contents).ok()) { // Do not propagate errors since meta info is not needed for operation return; } Block* meta = new Block(contents); Iterator* iter = meta->NewIterator(BytewiseComparator()); std::string key = "filter."; key.append(rep_->options.filter_policy->Name()); iter->Seek(key); if (iter->Valid() && iter->key() == Slice(key)) { ReadFilter(iter->value()); } delete iter; delete meta; }
// Convert an index iterator value (i.e., an encoded BlockHandle) // into an iterator over the contents of the corresponding block. Iterator* Table::BlockReader(void* arg, const ReadOptions& options, const Slice& index_value) { Table* table = reinterpret_cast<Table*>(arg); Cache* block_cache = table->rep_->options.block_cache; Block* block = NULL; Cache::Handle* cache_handle = NULL; BlockHandle handle; Slice input = index_value; Status s = handle.DecodeFrom(&input); // We intentionally allow extra stuff in index_value so that we // can add more features in the future. if (s.ok()) { BlockContents contents; if (block_cache != NULL) { char cache_key_buffer[16]; EncodeFixed64(cache_key_buffer, table->rep_->cache_id); EncodeFixed64(cache_key_buffer+8, handle.offset()); Slice key(cache_key_buffer, sizeof(cache_key_buffer)); cache_handle = block_cache->Lookup(key); if (cache_handle != NULL) { block = reinterpret_cast<Block*>(block_cache->Value(cache_handle)); } else { s = ReadBlock(table->rep_->file, options, handle, &contents); if (s.ok()) { block = new Block(contents); if (contents.cachable && options.fill_cache) { cache_handle = block_cache->Insert( key, block, block->size(), &DeleteCachedBlock); } } } } else { s = ReadBlock(table->rep_->file, options, handle, &contents); if (s.ok()) { block = new Block(contents); } } } Iterator* iter; if (block != NULL) { iter = block->NewIterator(table->rep_->options.comparator); if (cache_handle == NULL) { iter->RegisterCleanup(&DeleteBlock, block, NULL); } else { iter->RegisterCleanup(&ReleaseBlock, block_cache, cache_handle); } } else { iter = NewErrorIterator(s); } return iter; }