{"id":1687,"date":"2022-11-24T18:48:44","date_gmt":"2022-11-24T10:48:44","guid":{"rendered":"https:\/\/qaqaq.top\/?p=1687"},"modified":"2022-11-27T12:40:57","modified_gmt":"2022-11-27T04:40:57","slug":"1687","status":"publish","type":"post","link":"https:\/\/qaqaq.top\/?p=1687","title":{"rendered":"MVCC\u89e3\u51b3\u8bfb\u5199\u95ee\u9898\u3001MVCC\u4e09\u5251\u5ba2\uff1a\u9690\u85cf\u5b57\u6bb5\u3001UndoLog\u7248\u672c\u94fe\u3001ReadView\u89c4\u5219\u3001MVCC\u5728\u8bfb\u5df2\u63d0\u4ea4\u548c\u53ef\u91cd\u590d\u8bfb\u9694\u79bb\u7ea7\u522b\u4e0b\u7684\u64cd\u4f5c\u6d41\u7a0b\u3001MVCC\u5728\u53ef\u91cd\u590d\u8bfb\u4e0b\u89e3\u51b3\u5e7b\u8bfb\u7684\u6d41\u7a0b"},"content":{"rendered":"\n
# \u7b2c16\u7ae0_\u591a\u7248\u672c\u5e76\u53d1\u63a7\u5236\n\n# 1. \u4ec0\u4e48\u662fMVCC\n\n# MVCC \uff08Multiversion Concurrency Control\uff09\uff0c\u591a\u7248\u672c\u5e76\u53d1\u63a7\u5236\u3002\u987e\u540d\u601d\u4e49\uff0c\n# MVCC \u662f\u901a\u8fc7\u6570\u636e\u884c\u7684\u591a\u4e2a\u7248\u672c\u7ba1\u7406\u6765\u5b9e\u73b0\u6570\u636e\u5e93\u7684 \u5e76\u53d1\u63a7\u5236 \u3002\n# \u8fd9\u9879\u6280\u672f\u4f7f\u5f97\u5728InnoDB\u7684\u4e8b\u52a1\u9694\u79bb\u7ea7\u522b\u4e0b\u6267\u884c \u4e00\u81f4\u6027\u8bfb \u64cd\u4f5c\u6709\u4e86\u4fdd\u8bc1\u3002\u6362\u8a00\u4e4b\uff0c\n# \u5c31\u662f\u4e3a\u4e86\u67e5\u8be2\u4e00\u4e9b\u6b63\u5728\u88ab\u53e6\u4e00\u4e2a\u4e8b\u52a1\u66f4\u65b0\u7684\u884c\uff0c\u5e76\u4e14\u53ef\u4ee5\u770b\u5230\u5b83\u4eec\u88ab\u66f4\u65b0\u4e4b\u524d\u7684\u503c\uff0c\n# \u8fd9\u6837\u5728\u505a\u67e5\u8be2\u7684\u65f6\u5019\u5c31\u4e0d\u7528\u7b49\u5f85\u53e6\u4e00\u4e2a\u4e8b\u52a1\u91ca\u653e\u9501\u3002\n\n# 2. \u5feb\u7167\u8bfb\u4e0e\u5f53\u524d\u8bfb\n\n# MVCC\u5728MySQL InnoDB\u4e2d\u7684\u5b9e\u73b0\u4e3b\u8981\u662f\u4e3a\u4e86\u63d0\u9ad8\u6570\u636e\u5e93\u5e76\u53d1\u6027\u80fd\uff0c\u7528\u66f4\u597d\u7684\u65b9\u5f0f\u53bb\u5904\u7406 \u8bfb-\u5199\u51b2\u7a81 \uff0c\n# \u505a\u5230\u5373\u4f7f\u6709\u8bfb\u5199\u51b2\u7a81\u65f6\uff0c\u4e5f\u80fd\u505a\u5230 \u4e0d\u52a0\u9501 \uff0c \u975e\u963b\u585e\u5e76\u53d1\u8bfb \uff0c\u800c\u8fd9\u4e2a\u8bfb\u6307\u7684\u5c31\u662f \u5feb\u7167\u8bfb , \u800c\u975e \u5f53\u524d\u8bfb \u3002\n# \u5f53\u524d\u8bfb\u5b9e\u9645\u4e0a\u662f\u4e00\u79cd\u52a0\u9501\u7684\u64cd\u4f5c\uff0c\u662f\u60b2\u89c2\u9501\u7684\u5b9e\u73b0\u3002\u800cMVCC\u672c\u8d28\u662f\u91c7\u7528\u4e50\u89c2\u9501\u601d\u60f3\u7684\u4e00\u79cd\u65b9\u5f0f\u3002\n\n# 2.1 \u5feb\u7167\u8bfb\n# \u5feb\u7167\u8bfb\u53c8\u53eb\u4e00\u81f4\u6027\u8bfb\uff0c\u8bfb\u53d6\u7684\u662f\u5feb\u7167\u6570\u636e\u3002\u4e0d\u52a0\u9501\u7684\u7b80\u5355\u7684 SELECT \u90fd\u5c5e\u4e8e\u5feb\u7167\u8bfb\uff0c\u5373\u4e0d\u52a0\u9501\u7684\u975e\u963b\u585e\u8bfb\uff1b\u6bd4\u5982\u8fd9\u6837\uff1a\n# SELECT * FROM player WHERE ...\n\n# \u4e4b\u6240\u4ee5\u51fa\u73b0\u5feb\u7167\u8bfb\u7684\u60c5\u51b5\uff0c\u662f\u57fa\u4e8e\u63d0\u9ad8\u5e76\u53d1\u6027\u80fd\u7684\u8003\u8651\uff0c\u5feb\u7167\u8bfb\u7684\u5b9e\u73b0\u662f\u57fa\u4e8eMVCC\uff0c\u5b83\u5728\u5f88\u591a\u60c5\u51b5\u4e0b\uff0c\n# \u907f\u514d\u4e86\u52a0\u9501\u64cd\u4f5c\uff0c\u964d\u4f4e\u4e86\u5f00\u9500\u3002\n\n# \u65e2\u7136\u662f\u57fa\u4e8e\u591a\u7248\u672c\uff0c\u90a3\u4e48\u5feb\u7167\u8bfb\u53ef\u80fd\u8bfb\u5230\u7684\u5e76\u4e0d\u4e00\u5b9a\u662f\u6570\u636e\u7684\u6700\u65b0\u7248\u672c\uff0c\u800c\u6709\u53ef\u80fd\u662f\u4e4b\u524d\u7684\u5386\u53f2\u7248\u672c\u3002\n\n# \u5feb\u7167\u8bfb\u7684\u524d\u63d0\u662f\u9694\u79bb\u7ea7\u522b\u4e0d\u662f\u4e32\u884c\u7ea7\u522b\uff0c\u4e32\u884c\u7ea7\u522b\u4e0b\u7684\u5feb\u7167\u8bfb\u4f1a\u9000\u5316\u6210\u5f53\u524d\u8bfb\u3002\n\n# 2.2 \u5f53\u524d\u8bfb\n# \u5f53\u524d\u8bfb\u8bfb\u53d6\u7684\u662f\u8bb0\u5f55\u7684\u6700\u65b0\u7248\u672c\uff08\u6700\u65b0\u6570\u636e\uff0c\u800c\u4e0d\u662f\u5386\u53f2\u7248\u672c\u7684\u6570\u636e\uff09\uff0c\n# \u8bfb\u53d6\u65f6\u8fd8\u8981\u4fdd\u8bc1\u5176\u4ed6\u5e76\u53d1\u4e8b\u52a1\u4e0d\u80fd\u4fee\u6539\u5f53\u524d\u8bb0\u5f55\uff0c\u4f1a\u5bf9\u8bfb\u53d6\u7684\u8bb0\u5f55\u8fdb\u884c\u52a0\u9501\u3002\n# \u52a0\u9501\u7684 SELECT\uff0c\u6216\u8005\u5bf9\u6570\u636e\u8fdb\u884c\u589e\u5220\u6539\u90fd\u4f1a\u8fdb\u884c\u5f53\u524d\u8bfb\u3002\u6bd4\u5982\uff1a\n# SELECT * FROM student LOCK IN SHARE MODE; # \u5171\u4eab\u9501\n# SELECT * FROM student FOR UPDATE; # \u6392\u4ed6\u9501\n# INSERT INTO student values ... # \u6392\u4ed6\u9501\n# DELETE FROM student WHERE ... # \u6392\u4ed6\u9501\n# UPDATE student SET ... # \u6392\u4ed6\u9501\n\n# 3. \u590d\u4e60\n# 3.1 \u518d\u8c08\u9694\u79bb\u7ea7\u522b\n\n# SQL\n\n# \u8bfb\u672a\u63d0\u4ea4  ----------------------------------  (\u9694\u79bb\u7ebf)\n#                         \u810f\u8bfb\n# \u8bfb\u5df2\u63d0\u4ea4  ----------------------------------\n#                     \u4e0d\u53ef\u91cd\u590d\u8bfb\n# \u53ef\u91cd\u590d\u8bfb  ----------------------------------\n#                         \u5e7b\u8bfb\n# \u4e32\u884c\u5316    ----------------------------------\n\n#MySQL\n\n# \u8bfb\u672a\u63d0\u4ea4  ----------------------------------  (\u9694\u79bb\u7ebf)\n#                         \u810f\u8bfb\n# \u8bfb\u5df2\u63d0\u4ea4  ----------------------------------\n#                 \u4e0d\u53ef\u91cd\u590d\u8bfb\uff0c\u5e7b\u8bfb\n# \u53ef\u91cd\u590d\u8bfb  ----------------------------------  \u91c7\u7528MVCC+\n#  \/\u4e32\u884c\u5316                                      Next-Key Lock\n\n# 3.2 \u9690\u85cf\u5b57\u6bb5\u3001Undo Log\u7248\u672c\u94fe\n# \u56de\u987e\u4e00\u4e0bundo\u65e5\u5fd7\u7684\u7248\u672c\u94fe\uff0c\u5bf9\u4e8e\u4f7f\u7528 InnoDB \u5b58\u50a8\u5f15\u64ce\u7684\u8868\u6765\u8bf4\uff0c\u5b83\u7684\u805a\u7c07\u7d22\u5f15\u8bb0\u5f55\u4e2d\u90fd\u5305\u542b\u4e24\u4e2a\u5fc5\u8981\u7684\u9690\u85cf\u5217\u3002\n#     trx_id \uff1a\u6bcf\u6b21\u4e00\u4e2a\u4e8b\u52a1\u5bf9\u67d0\u6761\u805a\u7c07\u7d22\u5f15\u8bb0\u5f55\u8fdb\u884c\u6539\u52a8\u65f6\uff0c\u90fd\u4f1a\u628a\u8be5\u4e8b\u52a1\u7684 \u4e8b\u52a1id \u8d4b\u503c\u7ed9trx_id \u9690\u85cf\u5217\u3002\n#     roll_pointer \uff1a\u6bcf\u6b21\u5bf9\u67d0\u6761\u805a\u7c07\u7d22\u5f15\u8bb0\u5f55\u8fdb\u884c\u6539\u52a8\u65f6\uff0c\u90fd\u4f1a\u628a\u65e7\u7684\u7248\u672c\u5199\u5165\u5230 undo\u65e5\u5fd7 \u4e2d\uff0c\n# \u7136\u540e\u8fd9\u4e2a\u9690\u85cf\u5217\u5c31\u76f8\u5f53\u4e8e\u4e00\u4e2a\u6307\u9488\uff0c\u53ef\u4ee5\u901a\u8fc7\u5b83\u6765\u627e\u5230\u8be5\u8bb0\u5f55\u4fee\u6539\u524d\u7684\u4fe1\u606f\u3002\n\n# insert undo\u53ea\u5728\u4e8b\u52a1\u56de\u6eda\u65f6\u8d77\u4f5c\u7528\uff0c\u5f53\u4e8b\u52a1\u63d0\u4ea4\u540e\uff0c\u8be5\u7c7b\u578b\u7684undo\u65e5\u5fd7\u5c31\u6ca1\u7528\u4e86\uff0c\n# \u5b83\u5360\u7528\u7684UndoLog Segment\u4e5f\u4f1a\u88ab\u7cfb\u7edf\u56de\u6536\uff08\u4e5f\u5c31\u662f\u8be5undo\u65e5\u5fd7\u5360\u7528\u7684Undo\u9875\u9762\u94fe\u8868\u8981\u4e48\u88ab\u91cd\u7528\uff0c\u8981\u4e48\u88ab\u91ca\u653e\uff09\u3002\n\n# 4. MVCC\u5b9e\u73b0\u539f\u7406\u4e4bReadView\n\n# MVCC \u7684\u5b9e\u73b0\u4f9d\u8d56\u4e8e\uff1a\u9690\u85cf\u5b57\u6bb5\u3001Undo Log\u3001Read View\u3002\n\n# 4.1 \u4ec0\u4e48\u662fReadView\n\n# 4.2 \u8bbe\u8ba1\u601d\u8def\n# \u4f7f\u7528 READ UNCOMMITTED \u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\uff0c\u7531\u4e8e\u53ef\u4ee5\u8bfb\u5230\u672a\u63d0\u4ea4\u4e8b\u52a1\u4fee\u6539\u8fc7\u7684\u8bb0\u5f55\uff0c\n# \u6240\u4ee5\u76f4\u63a5\u8bfb\u53d6\u8bb0\u5f55\u7684\u6700\u65b0\u7248\u672c\u5c31\u597d\u4e86\u3002\n\n# \u4f7f\u7528 SERIALIZABLE \u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\uff0cInnoDB\u89c4\u5b9a\u4f7f\u7528\u52a0\u9501\u7684\u65b9\u5f0f\u6765\u8bbf\u95ee\u8bb0\u5f55\u3002\n\n# \u4f7f\u7528 READ COMMITTED \u548c REPEATABLE READ \u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\uff0c\u90fd\u5fc5\u987b\u4fdd\u8bc1\u8bfb\u5230 \u5df2\u7ecf\u63d0\u4ea4\u4e86\u7684 \u4e8b\u52a1\u4fee\u6539\u8fc7\u7684\u8bb0\u5f55\u3002\n# \u5047\u5982\u53e6\u4e00\u4e2a\u4e8b\u52a1\u5df2\u7ecf\u4fee\u6539\u4e86\u8bb0\u5f55\u4f46\u662f\u5c1a\u672a\u63d0\u4ea4\uff0c\u662f\u4e0d\u80fd\u76f4\u63a5\u8bfb\u53d6\u6700\u65b0\u7248\u672c\u7684\u8bb0\u5f55\u7684\uff0c\n# \u6838\u5fc3\u95ee\u9898\u5c31\u662f\u9700\u8981\u5224\u65ad\u4e00\u4e0b\u7248\u672c\u94fe\u4e2d\u7684\u54ea\u4e2a\u7248\u672c\u662f\u5f53\u524d\u4e8b\u52a1\u53ef\u89c1\u7684\uff0c\u8fd9\u662fReadView\u8981\u89e3\u51b3\u7684\u4e3b\u8981\u95ee\u9898\u3002\n\n# \u8fd9\u4e2aReadView\u4e2d\u4e3b\u8981\u5305\u542b4\u4e2a\u6bd4\u8f83\u91cd\u8981\u7684\u5185\u5bb9\uff0c\u5206\u522b\u5982\u4e0b\uff1a\n# 1. creator_trx_id \uff0c\u521b\u5efa\u8fd9\u4e2a Read View \u7684\u4e8b\u52a1 ID\u3002\n# \u8bf4\u660e\uff1a\u53ea\u6709\u5728\u5bf9\u8868\u4e2d\u7684\u8bb0\u5f55\u505a\u6539\u52a8\u65f6\uff08\u6267\u884cINSERT\u3001DELETE\u3001UPDATE\u8fd9\u4e9b\u8bed\u53e5\u65f6\uff09\u624d\u4f1a\u4e3a\u4e8b\u52a1\u5206\u914d\u4e8b\u52a1id\uff0c\n# \u5426\u5219\u5728\u4e00\u4e2a\u53ea\u8bfb\u4e8b\u52a1\u4e2d\u7684\u4e8b\u52a1id\u503c\u90fd\u9ed8\u8ba4\u4e3a0\u3002\n\n# 2. trx_ids \uff0c\u8868\u793a\u5728\u751f\u6210ReadView\u65f6\u5f53\u524d\u7cfb\u7edf\u4e2d\u6d3b\u8dc3\u7684\u8bfb\u5199\u4e8b\u52a1\u7684 \u4e8b\u52a1id\u5217\u8868 \u3002\n\n# 3. up_limit_id \uff0c\u6d3b\u8dc3\u7684\u4e8b\u52a1\u4e2d\u6700\u5c0f\u7684\u4e8b\u52a1 ID\u3002\n\n# 4. low_limit_id \uff0c\u8868\u793a\u751f\u6210ReadView\u65f6\u7cfb\u7edf\u4e2d\u5e94\u8be5\u5206\u914d\u7ed9\u4e0b\u4e00\u4e2a\u4e8b\u52a1\u7684 id \u503c\u3002\n# low_limit_id \u662f\u7cfb\u7edf\u6700\u5927\u7684\u4e8b\u52a1id\u503c\uff0c\u8fd9\u91cc\u8981\u6ce8\u610f\u662f\u7cfb\u7edf\u4e2d\u7684\u4e8b\u52a1id\uff0c\u9700\u8981\u533a\u522b\u4e8e\u6b63\u5728\u6d3b\u8dc3\u7684\u4e8b\u52a1ID\u3002\n\n# \u6ce8\u610f\uff1alow_limit_id\u5e76\u4e0d\u662ftrx_ids\u4e2d\u7684\u6700\u5927\u503c\uff0c\u4e8b\u52a1id\u662f\u9012\u589e\u5206\u914d\u7684\u3002\u6bd4\u5982\uff0c\u73b0\u5728\u6709id\u4e3a1\uff0c2\uff0c3\u8fd9\u4e09\u4e2a\u4e8b\u52a1\uff0c\n# \u4e4b\u540eid\u4e3a3\u7684\u4e8b\u52a1\u63d0\u4ea4\u4e86\u3002\u90a3\u4e48\u4e00\u4e2a\u65b0\u7684\u8bfb\u4e8b\u52a1\u5728\u751f\u6210ReadView\u65f6\uff0ctrx_ids\u5c31\u5305\u62ec1\u548c2\uff0cup_limit_id\u7684\u503c\u5c31\u662f1\uff0c\n# low_limit_id\u7684\u503c\u5c31\u662f4\u3002\n\n# 4.3 ReadView\u7684\u89c4\u5219\n# \u6709\u4e86\u8fd9\u4e2aReadView\uff0c\u8fd9\u6837\u5728\u8bbf\u95ee\u67d0\u6761\u8bb0\u5f55\u65f6\uff0c\u53ea\u9700\u8981\u6309\u7167\u4e0b\u8fb9\u7684\u6b65\u9aa4\u5224\u65ad\u8bb0\u5f55\u7684\u67d0\u4e2a\u7248\u672c\u662f\u5426\u53ef\u89c1\u3002\n\n# \u5982\u679c\u88ab\u8bbf\u95ee\u7248\u672c\u7684trx_id\u5c5e\u6027\u503c\u4e0eReadView\u4e2d\u7684 creator_trx_id \u503c\u76f8\u540c\uff0c\n# \u610f\u5473\u7740\u5f53\u524d\u4e8b\u52a1\u5728\u8bbf\u95ee\u5b83\u81ea\u5df1\u4fee\u6539\u8fc7\u7684\u8bb0\u5f55\uff0c\u6240\u4ee5\u8be5\u7248\u672c\u53ef\u4ee5\u88ab\u5f53\u524d\u4e8b\u52a1\u8bbf\u95ee\u3002\n\n# \u5982\u679c\u88ab\u8bbf\u95ee\u7248\u672c\u7684trx_id\u5c5e\u6027\u503c\u5c0f\u4e8eReadView\u4e2d\u7684 up_limit_id \u503c\uff0c\n# \u8868\u660e\u751f\u6210\u8be5\u7248\u672c\u7684\u4e8b\u52a1\u5728\u5f53\u524d\u4e8b\u52a1\u751f\u6210ReadView\u524d\u5df2\u7ecf\u63d0\u4ea4\uff0c\u6240\u4ee5\u8be5\u7248\u672c\u53ef\u4ee5\u88ab\u5f53\u524d\u4e8b\u52a1\u8bbf\u95ee\u3002\n\n# \u5982\u679c\u88ab\u8bbf\u95ee\u7248\u672c\u7684trx_id\u5c5e\u6027\u503c\u5927\u4e8e\u6216\u7b49\u4e8eReadView\u4e2d\u7684 low_limit_id \u503c\uff0c\n# \u8868\u660e\u751f\u6210\u8be5\u7248\u672c\u7684\u4e8b\u52a1\u5728\u5f53\u524d\u4e8b\u52a1\u751f\u6210ReadView\u540e\u624d\u5f00\u542f\uff0c\u6240\u4ee5\u8be5\u7248\u672c\u4e0d\u53ef\u4ee5\u88ab\u5f53\u524d\u4e8b\u52a1\u8bbf\u95ee\u3002\n\n# \u5982\u679c\u88ab\u8bbf\u95ee\u7248\u672c\u7684trx_id\u5c5e\u6027\u503c\u5728ReadView\u7684 up_limit_id \u548c low_limit_id \u4e4b\u95f4\uff0c\n# \u90a3\u5c31\u9700\u8981\u5224\u65ad\u4e00\u4e0btrx_id\u5c5e\u6027\u503c\u662f\u4e0d\u662f\u5728 trx_ids \u5217\u8868\u4e2d\u3002\n\n# 4.4 MVCC\u6574\u4f53\u64cd\u4f5c\u6d41\u7a0b\n# \u4e86\u89e3\u4e86\u8fd9\u4e9b\u6982\u5ff5\u4e4b\u540e\uff0c\u6211\u4eec\u6765\u770b\u4e0b\u5f53\u67e5\u8be2\u4e00\u6761\u8bb0\u5f55\u7684\u65f6\u5019\uff0c\u7cfb\u7edf\u5982\u4f55\u901a\u8fc7MVCC\u627e\u5230\u5b83\uff1a\n\n# 1. \u9996\u5148\u83b7\u53d6\u4e8b\u52a1\u81ea\u5df1\u7684\u7248\u672c\u53f7\uff0c\u4e5f\u5c31\u662f\u4e8b\u52a1 ID\uff1b\n# 2. \u83b7\u53d6 ReadView\uff1b\n# 3. \u67e5\u8be2\u5f97\u5230\u7684\u6570\u636e\uff0c\u7136\u540e\u4e0e ReadView \u4e2d\u7684\u4e8b\u52a1\u7248\u672c\u53f7\u8fdb\u884c\u6bd4\u8f83\uff1b\n# 4. \u5982\u679c\u4e0d\u7b26\u5408 ReadView \u89c4\u5219\uff0c\u5c31\u9700\u8981\u4ece Undo Log \u4e2d\u83b7\u53d6\u5386\u53f2\u5feb\u7167\uff1b\n# 5. \u6700\u540e\u8fd4\u56de\u7b26\u5408\u89c4\u5219\u7684\u6570\u636e\u3002\n\n# \u5728\u9694\u79bb\u7ea7\u522b\u4e3a\u8bfb\u5df2\u63d0\u4ea4\uff08Read Committed\uff09\u65f6\uff0c\u4e00\u4e2a\u4e8b\u52a1\u4e2d\u7684\u6bcf\u4e00\u6b21 SELECT \u67e5\u8be2\u90fd\u4f1a\u91cd\u65b0\u83b7\u53d6\u4e00\u6b21Read View\u3002\n\n# \u6ce8\u610f\uff0c\u6b64\u65f6\u540c\u6837\u7684\u67e5\u8be2\u8bed\u53e5\u90fd\u4f1a\u91cd\u65b0\u83b7\u53d6\u4e00\u6b21 Read View\uff0c\u8fd9\u65f6\u5982\u679c Read View \u4e0d\u540c\uff0c\n# \u5c31\u53ef\u80fd\u4ea7\u751f\u4e0d\u53ef\u91cd\u590d\u8bfb\u6216\u8005\u5e7b\u8bfb\u7684\u60c5\u51b5\u3002\n\n# \u5f53\u9694\u79bb\u7ea7\u522b\u4e3a\u53ef\u91cd\u590d\u8bfb\u7684\u65f6\u5019\uff0c\u5c31\u907f\u514d\u4e86\u4e0d\u53ef\u91cd\u590d\u8bfb\uff0c\n# \u8fd9\u662f\u56e0\u4e3a\u4e00\u4e2a\u4e8b\u52a1\u53ea\u5728\u7b2c\u4e00\u6b21 SELECT \u7684\u65f6\u5019\u4f1a\u83b7\u53d6\u4e00\u6b21 Read View\uff0c\n# \u800c\u540e\u9762\u6240\u6709\u7684 SELECT \u90fd\u4f1a\u590d\u7528\u8fd9\u4e2a Read View\n\n# 5. \u4e3e\u4f8b\u8bf4\u660e\n\n# 5.1 READ COMMITTED\u9694\u79bb\u7ea7\u522b\u4e0b\n# READ COMMITTED \uff1a\u6bcf\u6b21\u8bfb\u53d6\u6570\u636e\u524d\u90fd\u751f\u6210\u4e00\u4e2aReadView\u3002\n\n# 5.2 REPEATABLE READ\u9694\u79bb\u7ea7\u522b\u4e0b\n# \u4f7f\u7528 REPEATABLE READ \u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\u6765\u8bf4\uff0c\u53ea\u4f1a\u5728\u7b2c\u4e00\u6b21\u6267\u884c\u67e5\u8be2\u8bed\u53e5\u65f6\u751f\u6210\u4e00\u4e2a ReadView \uff0c\n# \u4e4b\u540e\u7684\u67e5\u8be2\u5c31\u4e0d\u4f1a\u91cd\u590d\u751f\u6210\u4e86\u3002\n\n# 5.3 \u5982\u4f55\u89e3\u51b3\u5e7b\u8bfb\n\n# 6. \u603b\u7ed3\n\n# \u8fd9\u91cc\u4ecb\u7ecd\u4e86 MVCC \u5728 READ COMMITTD \u3001\n# REPEATABLE READ \u8fd9\u4e24\u79cd\u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\u5728\u6267\u884c\u5feb\u7167\u8bfb\u64cd\u4f5c\u65f6\u8bbf\u95ee\u8bb0\u5f55\u7684\u7248\u672c\u94fe\u7684\u8fc7\u7a0b\u3002\u8fd9\n# \u6837\u4f7f\u4e0d\u540c\u4e8b\u52a1\u7684 \u8bfb-\u5199 \u3001 \u5199-\u8bfb \u64cd\u4f5c\u5e76\u53d1\u6267\u884c\uff0c\u4ece\u800c\u63d0\u5347\u7cfb\u7edf\u6027\u80fd\u3002\n\n# \u6838\u5fc3\u70b9\u5728\u4e8e ReadView \u7684\u539f\u7406\uff0c\n# READ COMMITTD \u3001 REPEATABLE READ \u8fd9\u4e24\u4e2a\u9694\u79bb\u7ea7\u522b\u7684\u4e00\u4e2a\u5f88\u5927\u4e0d\u540c\u5c31\u662f\u751f\u6210ReadView\u7684\u65f6\u673a\u4e0d\u540c\uff1a\n#     READ COMMITTD \u5728\u6bcf\u4e00\u6b21\u8fdb\u884c\u666e\u901aSELECT\u64cd\u4f5c\u524d\u90fd\u4f1a\u751f\u6210\u4e00\u4e2aReadView\n#     REPEATABLE READ \u53ea\u5728\u7b2c\u4e00\u6b21\u8fdb\u884c\u666e\u901aSELECT\u64cd\u4f5c\u524d\u751f\u6210\u4e00\u4e2aReadView\uff0c\n# \u4e4b\u540e\u7684\u67e5\u8be2\u64cd\u4f5c\u90fd\u91cd\u590d\u4f7f\u7528\u8fd9\u4e2aReadView\u5c31\u597d\u4e86\u3002\n<\/code><\/pre>\n\n\n\n
5. \u4e3e\u4f8b\u8bf4\u660e<\/h3>\n\n\n\n
5.1 READ COMMITTED\u9694\u79bb\u7ea7\u522b\u4e0b<\/h4>\n\n\n\n
READ COMMITTED \uff1a\u6bcf\u6b21\u8bfb\u53d6\u6570\u636e\u524d\u90fd\u751f\u6210\u4e00\u4e2aReadView\u3002
\u73b0\u5728\u6709\u4e24\u4e2a \u4e8b\u52a1id \u5206\u522b\u4e3a 10 \u3001 20 \u7684\u4e8b\u52a1\u5728\u6267\u884c\uff1a<\/p>\n\n\n\n
# Transaction 10\nBEGIN;\nUPDATE student SET name=\"\u674e\u56db\" WHERE id=1;\nUPDATE student SET name=\"\u738b\u4e94\" WHERE id=1;\n# Transaction 20\nBEGIN;\n# \u66f4\u65b0\u4e86\u4e00\u4e9b\u522b\u7684\u8868\u7684\u8bb0\u5f55\n...<\/code><\/pre>\n\n\n\n
\u6b64\u523b\uff0c\u8868student \u4e2d id \u4e3a 1 \u7684\u8bb0\u5f55\u5f97\u5230\u7684\u7248\u672c\u94fe\u8868\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u5047\u8bbe\u73b0\u5728\u6709\u4e00\u4e2a\u4f7f\u7528 READ COMMITTED \u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\u5f00\u59cb\u6267\u884c\uff1a<\/p>\n\n\n\n
# \u4f7f\u7528READ COMMITTED\u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\nBEGIN;\n# SELECT1\uff1aTransaction 10\u300120\u672a\u63d0\u4ea4\nSELECT * FROM student WHERE id = 1; # \u5f97\u5230\u7684\u5217name\u7684\u503c\u4e3a'\u5f20\u4e09'<\/code><\/pre>\n\n\n\n
\u4e4b\u540e\uff0c\u6211\u4eec\u628a \u4e8b\u52a1id \u4e3a 10 \u7684\u4e8b\u52a1\u63d0\u4ea4\u4e00\u4e0b\uff1a<\/p>\n\n\n\n
# Transaction 10\nBEGIN;\nUPDATE student SET name=\"\u674e\u56db\" WHERE id=1;\nUPDATE student SET name=\"\u738b\u4e94\" WHERE id=1;\nCOMMIT;<\/code><\/pre>\n\n\n\n
\u7136\u540e\u518d\u5230 \u4e8b\u52a1id \u4e3a 20 \u7684\u4e8b\u52a1\u4e2d\u66f4\u65b0\u4e00\u4e0b\u8868 student \u4e2d id \u4e3a 1 \u7684\u8bb0\u5f55\uff1a<\/p>\n\n\n\n
# Transaction 20\nBEGIN;\n# \u66f4\u65b0\u4e86\u4e00\u4e9b\u522b\u7684\u8868\u7684\u8bb0\u5f55\n...\nUPDATE student SET name=\"\u94b1\u4e03\" WHERE id=1;\nUPDATE student SET name=\"\u5b8b\u516b\" WHERE id=1;<\/code><\/pre>\n\n\n\n
\u6b64\u523b\uff0c\u8868student\u4e2d id \u4e3a 1 \u7684\u8bb0\u5f55\u7684\u7248\u672c\u94fe\u5c31\u957f\u8fd9\u6837\uff1a<\/p>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u7136\u540e\u518d\u5230\u521a\u624d\u4f7f\u7528 READ COMMITTED \u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\u4e2d\u7ee7\u7eed\u67e5\u627e\u8fd9\u4e2a id \u4e3a 1 \u7684\u8bb0\u5f55\uff0c\u5982\u4e0b\uff1a<\/p>\n\n\n\n
# \u4f7f\u7528READ COMMITTED\u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\nBEGIN;\n# SELECT1\uff1aTransaction 10\u300120\u5747\u672a\u63d0\u4ea4\nSELECT * FROM student WHERE id = 1; # \u5f97\u5230\u7684\u5217name\u7684\u503c\u4e3a'\u5f20\u4e09'\n# SELECT2\uff1aTransaction 10\u63d0\u4ea4\uff0cTransaction 20\u672a\u63d0\u4ea4\nSELECT * FROM student WHERE id = 1; # \u5f97\u5230\u7684\u5217name\u7684\u503c\u4e3a'\u738b\u4e94'<\/code><\/pre>\n\n\n\n
5.2 REPEATABLE READ\u9694\u79bb\u7ea7\u522b\u4e0b<\/h4>\n\n\n\n
\u4f7f\u7528 REPEATABLE READ \u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\u6765\u8bf4\uff0c\u53ea\u4f1a\u5728\u7b2c\u4e00\u6b21\u6267\u884c\u67e5\u8be2\u8bed\u53e5\u65f6\u751f\u6210\u4e00\u4e2a ReadView \uff0c\u4e4b
\u540e\u7684\u67e5\u8be2\u5c31\u4e0d\u4f1a\u91cd\u590d\u751f\u6210\u4e86\u3002
\u6bd4\u5982\uff0c\u7cfb\u7edf\u91cc\u6709\u4e24\u4e2a \u4e8b\u52a1id \u5206\u522b\u4e3a 10 \u3001 20 \u7684\u4e8b\u52a1\u5728\u6267\u884c\uff1a<\/p>\n\n\n\n
# Transaction 10\nBEGIN;\nUPDATE student SET name=\"\u674e\u56db\" WHERE id=1;\nUPDATE student SET name=\"\u738b\u4e94\" WHERE id=1;\n# Transaction 20\nBEGIN;\n# \u66f4\u65b0\u4e86\u4e00\u4e9b\u522b\u7684\u8868\u7684\u8bb0\u5f55\n...<\/code><\/pre>\n\n\n\n
\u6b64\u523b\uff0c\u8868student \u4e2d id \u4e3a 1 \u7684\u8bb0\u5f55\u5f97\u5230\u7684\u7248\u672c\u94fe\u8868\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u5047\u8bbe\u73b0\u5728\u6709\u4e00\u4e2a\u4f7f\u7528 REPEATABLE READ \u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\u5f00\u59cb\u6267\u884c\uff1a<\/p>\n\n\n\n
# \u4f7f\u7528REPEATABLE READ\u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\nBEGIN;\n# SELECT1\uff1aTransaction 10\u300120\u672a\u63d0\u4ea4\nSELECT * FROM student WHERE id = 1; # \u5f97\u5230\u7684\u5217name\u7684\u503c\u4e3a'\u5f20\u4e09'<\/code><\/pre>\n\n\n\n
\u4e4b\u540e\uff0c\u6211\u4eec\u628a \u4e8b\u52a1id \u4e3a 10 \u7684\u4e8b\u52a1\u63d0\u4ea4\u4e00\u4e0b\uff0c\u5c31\u50cf\u8fd9\u6837\uff1a<\/p>\n\n\n\n
# Transaction 10\nBEGIN;\nUPDATE student SET name=\"\u674e\u56db\" WHERE id=1;\nUPDATE student SET name=\"\u738b\u4e94\" WHERE id=1;\nCOMMIT;<\/code><\/pre>\n\n\n\n
\u7136\u540e\u518d\u5230 \u4e8b\u52a1id \u4e3a 20 \u7684\u4e8b\u52a1\u4e2d\u66f4\u65b0\u4e00\u4e0b\u8868 student \u4e2d id \u4e3a 1 \u7684\u8bb0\u5f55\uff1a<\/p>\n\n\n\n
# Transaction 20\nBEGIN;\n# \u66f4\u65b0\u4e86\u4e00\u4e9b\u522b\u7684\u8868\u7684\u8bb0\u5f55\n...\nUPDATE student SET name=\"\u94b1\u4e03\" WHERE id=1;\nUPDATE student SET name=\"\u5b8b\u516b\" WHERE id=1;<\/code><\/pre>\n\n\n\n
\u6b64\u523b\uff0c\u8868student \u4e2d id \u4e3a 1 \u7684\u8bb0\u5f55\u7684\u7248\u672c\u94fe\u957f\u8fd9\u6837\uff1a<\/p>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u7136\u540e\u518d\u5230\u521a\u624d\u4f7f\u7528 REPEATABLE READ \u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\u4e2d\u7ee7\u7eed\u67e5\u627e\u8fd9\u4e2a id \u4e3a 1 \u7684\u8bb0\u5f55\uff0c\u5982\u4e0b\uff1a<\/p>\n\n\n\n
# \u4f7f\u7528REPEATABLE READ\u9694\u79bb\u7ea7\u522b\u7684\u4e8b\u52a1\nBEGIN;\n# SELECT1\uff1aTransaction 10\u300120\u5747\u672a\u63d0\u4ea4\nSELECT * FROM student WHERE id = 1; # \u5f97\u5230\u7684\u5217name\u7684\u503c\u4e3a'\u5f20\u4e09'\n# SELECT2\uff1aTransaction 10\u63d0\u4ea4\uff0cTransaction 20\u672a\u63d0\u4ea4\nSELECT * FROM student WHERE id = 1; # \u5f97\u5230\u7684\u5217name\u7684\u503c\u4ecd\u4e3a'\u5f20\u4e09'<\/code><\/pre>\n\n\n\n
5.3 \u5982\u4f55\u89e3\u51b3\u5e7b\u8bfb<\/h4>\n\n\n\n
\u63a5\u4e0b\u6765\u8bf4\u660eInnoDB \u662f\u5982\u4f55\u89e3\u51b3\u5e7b\u8bfb\u7684\u3002
\u5047\u8bbe\u73b0\u5728\u8868 student \u4e2d\u53ea\u6709\u4e00\u6761\u6570\u636e\uff0c\u6570\u636e\u5185\u5bb9\u4e2d\uff0c\u4e3b\u952e id=1\uff0c\u9690\u85cf\u7684 trx_id=10\uff0c\u5b83\u7684 undo log \u5982\u4e0b\u56fe
\u6240\u793a\u3002<\/p>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u5047\u8bbe\u73b0\u5728\u6709\u4e8b\u52a1 A \u548c\u4e8b\u52a1 B \u5e76\u53d1\u6267\u884c\uff0c \u4e8b\u52a1 A \u7684\u4e8b\u52a1 id \u4e3a 20 \uff0c \u4e8b\u52a1 B \u7684\u4e8b\u52a1 id \u4e3a 30 \u3002
\u6b65\u9aa41\uff1a\u4e8b\u52a1 A \u5f00\u59cb\u7b2c\u4e00\u6b21\u67e5\u8be2\u6570\u636e\uff0c\u67e5\u8be2\u7684 SQL \u8bed\u53e5\u5982\u4e0b\u3002<\/p>\n\n\n\n
select * from student where id >= 1;<\/code><\/pre>\n\n\n\n
\u5728\u5f00\u59cb\u67e5\u8be2\u4e4b\u524d\uff0cMySQL \u4f1a\u4e3a\u4e8b\u52a1 A \u4ea7\u751f\u4e00\u4e2a ReadView\uff0c\u6b64\u65f6 ReadView \u7684\u5185\u5bb9\u5982\u4e0b\uff1a trx_ids=
[20,30] \uff0c up_limit_id=20 \uff0c low_limit_id=31 \uff0c creator_trx_id=20 \u3002<\/p>\n\n\n\n
\u7531\u4e8e\u6b64\u65f6\u8868 student \u4e2d\u53ea\u6709\u4e00\u6761\u6570\u636e\uff0c\u4e14\u7b26\u5408 where id>=1 \u6761\u4ef6\uff0c\u56e0\u6b64\u4f1a\u67e5\u8be2\u51fa\u6765\u3002\u7136\u540e\u6839\u636e ReadView
\u673a\u5236\uff0c\u53d1\u73b0\u8be5\u884c\u6570\u636e\u7684trx_id=10\uff0c\u5c0f\u4e8e\u4e8b\u52a1 A \u7684 ReadView \u91cc up_limit_id\uff0c\u8fd9\u8868\u793a\u8fd9\u6761\u6570\u636e\u662f\u4e8b\u52a1 A \u5f00
\u542f\u4e4b\u524d\uff0c\u5176\u4ed6\u4e8b\u52a1\u5c31\u5df2\u7ecf\u63d0\u4ea4\u4e86\u7684\u6570\u636e\uff0c\u56e0\u6b64\u4e8b\u52a1 A \u53ef\u4ee5\u8bfb\u53d6\u5230\u3002<\/p>\n\n\n\n
\u7ed3\u8bba\uff1a\u4e8b\u52a1 A \u7684\u7b2c\u4e00\u6b21\u67e5\u8be2\uff0c\u80fd\u8bfb\u53d6\u5230\u4e00\u6761\u6570\u636e\uff0cid=1\u3002<\/p>\n\n\n\n
\u6b65\u9aa42\uff1a\u63a5\u7740\u4e8b\u52a1 B(trx_id=30)\uff0c\u5f80\u8868 student \u4e2d\u65b0\u63d2\u5165\u4e24\u6761\u6570\u636e\uff0c\u5e76\u63d0\u4ea4\u4e8b\u52a1\u3002<\/p>\n\n\n\n
insert into student(id,name) values(2,'\u674e\u56db');\ninsert into student(id,name) values(3,'\u738b\u4e94');<\/code><\/pre>\n\n\n\n
\u6b64\u65f6\u8868student \u4e2d\u5c31\u6709\u4e09\u6761\u6570\u636e\u4e86\uff0c\u5bf9\u5e94\u7684 undo \u5982\u4e0b\u56fe\u6240\u793a\uff1a<\/p>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u6b65\u9aa43\uff1a\u63a5\u7740\u4e8b\u52a1 A \u5f00\u542f\u7b2c\u4e8c\u6b21\u67e5\u8be2\uff0c\u6839\u636e\u53ef\u91cd\u590d\u8bfb\u9694\u79bb\u7ea7\u522b\u7684\u89c4\u5219\uff0c\u6b64\u65f6\u4e8b\u52a1 A \u5e76\u4e0d\u4f1a\u518d\u91cd\u65b0\u751f\u6210
ReadView\u3002\u6b64\u65f6\u8868 student \u4e2d\u7684 3 \u6761\u6570\u636e\u90fd\u6ee1\u8db3 where id>=1 \u7684\u6761\u4ef6\uff0c\u56e0\u6b64\u4f1a\u5148\u67e5\u51fa\u6765\u3002\u7136\u540e\u6839\u636e
ReadView \u673a\u5236\uff0c\u5224\u65ad\u6bcf\u6761\u6570\u636e\u662f\u4e0d\u662f\u90fd\u53ef\u4ee5\u88ab\u4e8b\u52a1 A \u770b\u5230\u3002<\/p>\n\n\n\n
1\uff09\u9996\u5148 id=1 \u7684\u8fd9\u6761\u6570\u636e\uff0c\u524d\u9762\u5df2\u7ecf\u8bf4\u8fc7\u4e86\uff0c\u53ef\u4ee5\u88ab\u4e8b\u52a1 A \u770b\u5230\u3002
2\uff09\u7136\u540e\u662f id=2 \u7684\u6570\u636e\uff0c\u5b83\u7684 trx_id=30\uff0c\u6b64\u65f6\u4e8b\u52a1 A \u53d1\u73b0\uff0c\u8fd9\u4e2a\u503c\u5904\u4e8e up_limit_id \u548c low_limit_id \u4e4b
\u95f4\uff0c\u56e0\u6b64\u8fd8\u9700\u8981\u518d\u5224\u65ad 30 \u662f\u5426\u5904\u4e8e trx_ids \u6570\u7ec4\u5185\u3002\u7531\u4e8e\u4e8b\u52a1 A \u7684 trx_ids=[20,30]\uff0c\u56e0\u6b64\u5728\u6570\u7ec4\u5185\uff0c\u8fd9\u8868
\u793a id=2 \u7684\u8fd9\u6761\u6570\u636e\u662f\u4e0e\u4e8b\u52a1 A \u5728\u540c\u4e00\u65f6\u523b\u542f\u52a8\u7684\u5176\u4ed6\u4e8b\u52a1\u63d0\u4ea4\u7684\uff0c\u6240\u4ee5\u8fd9\u6761\u6570\u636e\u4e0d\u80fd\u8ba9\u4e8b\u52a1 A \u770b\u5230\u3002
3\uff09\u540c\u7406\uff0cid=3 \u7684\u8fd9\u6761\u6570\u636e\uff0ctrx_id \u4e5f\u4e3a 30\uff0c\u56e0\u6b64\u4e5f\u4e0d\u80fd\u88ab\u4e8b\u52a1 A \u770b\u89c1\u3002<\/p>\n\n\n\n
\"\"<\/div><\/figure>\n\n\n\n
\u7ed3\u8bba\uff1a\u6700\u7ec8\u4e8b\u52a1 A \u7684\u7b2c\u4e8c\u6b21\u67e5\u8be2\uff0c\u53ea\u80fd\u67e5\u8be2\u51fa id=1 \u7684\u8fd9\u6761\u6570\u636e\u3002\u8fd9\u548c\u4e8b\u52a1 A \u7684\u7b2c\u4e00\u6b21\u67e5\u8be2\u7684\u7ed3\u679c\u662f\u4e00\u6837
\u7684\uff0c\u56e0\u6b64\u6ca1\u6709\u51fa\u73b0\u5e7b\u8bfb\u73b0\u8c61\uff0c\u6240\u4ee5\u8bf4\u5728 MySQL \u7684\u53ef\u91cd\u590d\u8bfb\u9694\u79bb\u7ea7\u522b\u4e0b\uff0c\u4e0d\u5b58\u5728\u5e7b\u8bfb\u95ee\u9898\u3002<\/p>\n\n\n\n
<\/p>\n\n\n\n
\u9762\u8bd5\u91cd\u70b9<\/h3>\n\n\n\n
\"\"<\/div><\/figure>\n","protected":false},"excerpt":{"rendered":"
5. \u4e3e\u4f8b\u8bf4\u660e 5.1 READ COMMITTED\u9694\u79bb\u7ea7\u522b\u4e0b READ COMMITTED \uff1a\u6bcf\u6b21\u8bfb\u53d6\u6570\u636e\u524d […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[47],"class_list":["post-1687","post","type-post","status-publish","format-standard","hentry","category-mysql-code","tag-mysql"],"_links":{"self":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1687"}],"collection":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1687"}],"version-history":[{"count":3,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1687\/revisions"}],"predecessor-version":[{"id":1699,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1687\/revisions\/1699"}],"wp:attachment":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1687"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1687"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1687"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}