1 /* Copyright 2015 The TensorFlow Authors. All Rights Reserved. 2 3 Licensed under the Apache License, Version 2.0 (the "License"); 4 you may not use this file except in compliance with the License. 5 You may obtain a copy of the License at 6 7 http://www.apache.org/licenses/LICENSE-2.0 8 9 Unless required by applicable law or agreed to in writing, software 10 distributed under the License is distributed on an "AS IS" BASIS, 11 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 See the License for the specific language governing permissions and 13 limitations under the License. 14 ==============================================================================*/ 15 16 #include "tensorflow/core/lib/io/table.h" 17 18 #include "tensorflow/core/lib/core/coding.h" 19 #include "tensorflow/core/lib/core/errors.h" 20 #include "tensorflow/core/lib/io/block.h" 21 #include "tensorflow/core/lib/io/format.h" 22 #include "tensorflow/core/lib/io/table_options.h" 23 #include "tensorflow/core/lib/io/two_level_iterator.h" 24 #include "tensorflow/core/platform/env.h" 25 26 namespace tensorflow { 27 namespace table { 28 29 struct Table::Rep { 30 ~Rep() { delete index_block; } 31 32 Options options; 33 Status status; 34 RandomAccessFile* file; 35 // XXX uint64 cache_id; 36 37 BlockHandle metaindex_handle; // Handle to metaindex_block: saved from footer 38 Block* index_block; 39 }; 40 41 Status Table::Open(const Options& options, RandomAccessFile* file, uint64 size, 42 Table** table) { 43 *table = nullptr; 44 if (size < Footer::kEncodedLength) { 45 return errors::DataLoss("file is too short to be an sstable"); 46 } 47 48 char footer_space[Footer::kEncodedLength]; 49 StringPiece footer_input; 50 Status s = file->Read(size - Footer::kEncodedLength, Footer::kEncodedLength, 51 &footer_input, footer_space); 52 if (!s.ok()) return s; 53 54 Footer footer; 55 s = footer.DecodeFrom(&footer_input); 56 if (!s.ok()) return s; 57 58 // Read the index block 59 BlockContents contents; 60 Block* index_block = nullptr; 61 if (s.ok()) { 62 s = ReadBlock(file, footer.index_handle(), &contents); 63 if (s.ok()) { 64 index_block = new Block(contents); 65 } 66 } 67 68 if (s.ok()) { 69 // We've successfully read the footer and the index block: we're 70 // ready to serve requests. 71 Rep* rep = new Table::Rep; 72 rep->options = options; 73 rep->file = file; 74 rep->metaindex_handle = footer.metaindex_handle(); 75 rep->index_block = index_block; 76 // XXX rep->cache_id = (options.block_cache ? 77 // options.block_cache->NewId() : 0); 78 *table = new Table(rep); 79 } else { 80 if (index_block) delete index_block; 81 } 82 83 return s; 84 } 85 86 Table::~Table() { delete rep_; } 87 88 static void DeleteBlock(void* arg, void* ignored) { 89 delete reinterpret_cast<Block*>(arg); 90 } 91 92 // Convert an index iterator value (i.e., an encoded BlockHandle) 93 // into an iterator over the contents of the corresponding block. 94 Iterator* Table::BlockReader(void* arg, const StringPiece& index_value) { 95 Table* table = reinterpret_cast<Table*>(arg); 96 // Cache* block_cache = table->rep_->options.block_cache; 97 Block* block = nullptr; 98 // Cache::Handle* cache_handle = NULL; 99 100 BlockHandle handle; 101 StringPiece input = index_value; 102 Status s = handle.DecodeFrom(&input); 103 // We intentionally allow extra stuff in index_value so that we 104 // can add more features in the future. 105 106 if (s.ok()) { 107 BlockContents contents; 108 s = ReadBlock(table->rep_->file, handle, &contents); 109 if (s.ok()) { 110 block = new Block(contents); 111 } 112 } 113 114 Iterator* iter; 115 if (block != nullptr) { 116 iter = block->NewIterator(); 117 iter->RegisterCleanup(&DeleteBlock, block, nullptr); 118 } else { 119 iter = NewErrorIterator(s); 120 } 121 return iter; 122 } 123 124 Iterator* Table::NewIterator() const { 125 return NewTwoLevelIterator(rep_->index_block->NewIterator(), 126 &Table::BlockReader, const_cast<Table*>(this)); 127 } 128 129 Status Table::InternalGet(const StringPiece& k, void* arg, 130 void (*saver)(void*, const StringPiece&, 131 const StringPiece&)) { 132 Status s; 133 Iterator* iiter = rep_->index_block->NewIterator(); 134 iiter->Seek(k); 135 if (iiter->Valid()) { 136 BlockHandle handle; 137 Iterator* block_iter = BlockReader(this, iiter->value()); 138 block_iter->Seek(k); 139 if (block_iter->Valid()) { 140 (*saver)(arg, block_iter->key(), block_iter->value()); 141 } 142 s = block_iter->status(); 143 delete block_iter; 144 } 145 if (s.ok()) { 146 s = iiter->status(); 147 } 148 delete iiter; 149 return s; 150 } 151 152 uint64 Table::ApproximateOffsetOf(const StringPiece& key) const { 153 Iterator* index_iter = rep_->index_block->NewIterator(); 154 index_iter->Seek(key); 155 uint64 result; 156 if (index_iter->Valid()) { 157 BlockHandle handle; 158 StringPiece input = index_iter->value(); 159 Status s = handle.DecodeFrom(&input); 160 if (s.ok()) { 161 result = handle.offset(); 162 } else { 163 // Strange: we can't decode the block handle in the index block. 164 // We'll just return the offset of the metaindex block, which is 165 // close to the whole file size for this case. 166 result = rep_->metaindex_handle.offset(); 167 } 168 } else { 169 // key is past the last key in the file. Approximate the offset 170 // by returning the offset of the metaindex block (which is 171 // right near the end of the file). 172 result = rep_->metaindex_handle.offset(); 173 } 174 delete index_iter; 175 return result; 176 } 177 178 } // namespace table 179 } // namespace tensorflow 180
