\u7247\u65b9\u306e\u66f4\u65b0\u304c\u6d88\u3048\u308b<\/strong>\u73fe\u8c61\u3067\u3059\u3002<\/p>\nA: \u6b8b\u9ad8\u3092\u8aad\u3080 \u2192 1000\nB: \u6b8b\u9ad8\u3092\u8aad\u3080 \u2192 1000\nA: 1000 - 100 = 900 \u3092\u66f8\u304d\u8fbc\u3093\u3067\u30b3\u30df\u30c3\u30c8\nB: 1000 - 200 = 800 \u3092\u66f8\u304d\u8fbc\u3093\u3067\u30b3\u30df\u30c3\u30c8\n\u2192 \u6700\u7d42\u6b8b\u9ad8\u306f 800\uff08A \u306e\u51fa\u91d1 100 \u304c\u6d88\u3048\u305f\u3002\u6b63\u3057\u304f\u306f 700\uff09<\/pre>\n\u66f8\u304d\u8fbc\u307f\u30b9\u30ad\u30e5\u30fc<\/h3>\n
2\u3064\u306e\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u304c\u305d\u308c\u305e\u308c\u5225\u306e\u884c<\/strong>\u3092\u66f4\u65b0\u3059\u308b\u305f\u3081\u76f4\u63a5\u306f\u3076\u3064\u304b\u3089\u306a\u3044\u3082\u306e\u306e\u3001\u4e21\u65b9\u304c\u30b3\u30df\u30c3\u30c8\u3055\u308c\u305f\u7d50\u679c\u3001\u8907\u6570\u884c\u306b\u307e\u305f\u304c\u308b\u30eb\u30fc\u30eb\u304c\u58ca\u308c\u308b<\/strong>\u73fe\u8c61\u3067\u3059\u3002<\/p>\n\u30eb\u30fc\u30eb: \u5f53\u756a\u4e2d\u306e\u62c5\u5f53\u8005\u306f\u5e38\u306b1\u4eba\u4ee5\u4e0a\u3044\u308b\u3053\u3068\uff08\u73fe\u57282\u4eba\u304c\u5f53\u756a\u4e2d\uff09\nA: \u5f53\u756a\u4e2d\u306f2\u4eba \u2192 \u81ea\u5206\u3092\u5916\u3057\u3066\u3088\u3044\u3068\u5224\u65ad\u3057\u3001\u81ea\u5206\u3092 off \u306b\u3059\u308b\nB: \u5f53\u756a\u4e2d\u306f2\u4eba \u2192 \u81ea\u5206\u3092\u5916\u3057\u3066\u3088\u3044\u3068\u5224\u65ad\u3057\u3001\u81ea\u5206\u3092 off \u306b\u3059\u308b\n\u2192 \u4e21\u65b9\u30b3\u30df\u30c3\u30c8\u3055\u308c\u3001\u5f53\u756a\u304c0\u4eba\u306b\u306a\u308b<\/pre>\nSQL \u6a19\u6e96\u306e\u5206\u96e2\u30ec\u30d9\u30eb\u306f\u3001\u6700\u521d\u306e3\u3064\u306e\u73fe\u8c61\u3092\u3082\u3068\u306b\u5b9a\u7fa9\u3055\u308c\u3066\u3044\u307e\u3059\u3002\u4e00\u65b9\u3001\u5b9f\u52d9\u3067\u554f\u984c\u306b\u306a\u308a\u3084\u3059\u3044\u306e\u306f\u30ed\u30b9\u30c8\u30a2\u30c3\u30d7\u30c7\u30fc\u30c8\u3068\u66f8\u304d\u8fbc\u307f\u30b9\u30ad\u30e5\u30fc<\/strong>\u3067\u3059\u3002<\/p>\nSQL \u6a19\u6e96\u306e4\u3064\u306e\u5206\u96e2\u30ec\u30d9\u30eb<\/h2>\n
\n\n\n| \u5206\u96e2\u30ec\u30d9\u30eb<\/th>\n | \u30c0\u30fc\u30c6\u30a3\u30ea\u30fc\u30c9<\/th>\n | \u30ce\u30f3\u30ea\u30d4\u30fc\u30bf\u30d6\u30eb\u30ea\u30fc\u30c9<\/th>\n | \u30d5\u30a1\u30f3\u30c8\u30e0\u30ea\u30fc\u30c9<\/th>\n<\/tr>\n<\/thead>\n |
\n\n| READ UNCOMMITTED<\/td>\n | \u8d77\u3053\u308a\u3046\u308b<\/td>\n | \u8d77\u3053\u308a\u3046\u308b<\/td>\n | \u8d77\u3053\u308a\u3046\u308b<\/td>\n<\/tr>\n |
\n| READ COMMITTED<\/td>\n | \u8d77\u3053\u3089\u306a\u3044<\/td>\n | \u8d77\u3053\u308a\u3046\u308b<\/td>\n | \u8d77\u3053\u308a\u3046\u308b<\/td>\n<\/tr>\n |
\n| REPEATABLE READ<\/td>\n | \u8d77\u3053\u3089\u306a\u3044<\/td>\n | \u8d77\u3053\u3089\u306a\u3044<\/td>\n | \u8d77\u3053\u308a\u3046\u308b<\/td>\n<\/tr>\n |
\n| SERIALIZABLE<\/td>\n | \u8d77\u3053\u3089\u306a\u3044<\/td>\n | \u8d77\u3053\u3089\u306a\u3044<\/td>\n | \u8d77\u3053\u3089\u306a\u3044<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n \u4e0b\u306b\u884c\u304f\u307b\u3069\u5206\u96e2\u306f\u5f37\u304f\u306a\u308a\u307e\u3059\u3002\u305d\u306e\u4ee3\u308f\u308a\u3001\u5f85\u3061\uff08\u30ed\u30c3\u30af\uff09\u3084\u30a8\u30e9\u30fc\uff08\u76f4\u5217\u5316\u5931\u6557\uff09\u304c\u5897\u3048\u3001\u540c\u6642\u5b9f\u884c\u6027\u80fd\u306f\u4e0b\u304c\u308a\u3084\u3059\u304f\u306a\u308a\u307e\u3059\u3002<\/p>\n \u5b9f\u969b\u306e DB \u3067\u306e\u632f\u308b\u821e\u3044<\/h2>\n\u6a19\u6e96\u304c\u5b9a\u3081\u3066\u3044\u308b\u306e\u306f\u300c\u6700\u4f4e\u9650\u9632\u3050\u3079\u304d\u73fe\u8c61\u300d\u3060\u3051\u3067\u3059\u3002\u3069\u3046\u5b9f\u73fe\u3059\u308b\u304b\u306f DB \u3054\u3068\u306b\u9055\u3044\u3001\u6a19\u6e96\u3088\u308a\u5f37\u304f\u9632\u3050 DB \u3082\u3042\u308a\u307e\u3059\u3002<\/p>\n \n\n\n| DB<\/th>\n | \u30c7\u30d5\u30a9\u30eb\u30c8<\/th>\n | \u5b9f\u73fe\u65b9\u5f0f\u306e\u6982\u8981<\/th>\n<\/tr>\n<\/thead>\n | \n\n| PostgreSQL<\/td>\n | READ COMMITTED<\/td>\n | MVCC\u3002REPEATABLE READ \u306f\u30b9\u30ca\u30c3\u30d7\u30b7\u30e7\u30c3\u30c8\u5206\u96e2\u3001SERIALIZABLE \u306f SSI<\/td>\n<\/tr>\n | \n| MySQL\uff08InnoDB\uff09<\/td>\n | REPEATABLE READ<\/td>\n | MVCC \uff0b \u30cd\u30af\u30b9\u30c8\u30ad\u30fc\u30ed\u30c3\u30af \/ \u30ae\u30e3\u30c3\u30d7\u30ed\u30c3\u30af<\/td>\n<\/tr>\n | \n| Oracle Database<\/td>\n | READ COMMITTED<\/td>\n | MVCC\u3002SERIALIZABLE \u3082\u30b9\u30ca\u30c3\u30d7\u30b7\u30e7\u30c3\u30c8\u30d9\u30fc\u30b9<\/td>\n<\/tr>\n | \n| SQL Server<\/td>\n | READ COMMITTED<\/td>\n | \u30c7\u30d5\u30a9\u30eb\u30c8\u306f\u30ed\u30c3\u30af\u30d9\u30fc\u30b9\u3002READ_COMMITTED_SNAPSHOT \/ SNAPSHOT \u3067\u884c\u30d0\u30fc\u30b8\u30e7\u30cb\u30f3\u30b0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\nPostgreSQL \u306e\u7279\u5fb4<\/h3>\n\n- READ UNCOMMITTED \u3092\u6307\u5b9a\u3057\u3066\u3082\u3001READ COMMITTED \u3068\u540c\u3058\u52d5\u304d\u306b\u306a\u308a\u307e\u3059<\/li>\n
- READ COMMITTED \u306f\u6587\u3054\u3068<\/strong>\u3001REPEATABLE READ \u306f\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u306e\u6700\u521d\u306e\u6587\u306e\u6642\u70b9<\/strong>\u306e\u30b9\u30ca\u30c3\u30d7\u30b7\u30e7\u30c3\u30c8\u3092\u4f7f\u3044\u307e\u3059<\/li>\n
- REPEATABLE READ \u3067\u306f\u3001\u6a19\u6e96\u3067\u306f\u8a31\u3055\u308c\u3066\u3044\u308b\u30d5\u30a1\u30f3\u30c8\u30e0\u3082\u8d77\u304d\u307e\u305b\u3093<\/li>\n
- REPEATABLE READ \u3067\u3001\u4ed6\u8005\u304c\u5148\u306b\u66f4\u65b0\u3057\u3066\u30b3\u30df\u30c3\u30c8\u3057\u305f\u884c\u3092\u66f4\u65b0\u3057\u3088\u3046\u3068\u3059\u308b\u3068\u3001
could not serialize access due to concurrent update<\/code>\uff08SQLSTATE 40001<\/code>\uff09\u306b\u306a\u308a\u307e\u3059<\/li>\n- SERIALIZABLE\uff08SSI\uff09\u306f\u66f8\u304d\u8fbc\u307f\u30b9\u30ad\u30e5\u30fc\u3082\u691c\u51fa\u3057\u3066
40001<\/code> \u3067\u5931\u6557\u3055\u305b\u307e\u3059\u3002\u30ea\u30c8\u30e9\u30a4\u304c\u524d\u63d0<\/strong>\u3067\u3059<\/li>\n<\/ul>\nMySQL\uff08InnoDB\uff09\u306e\u7279\u5fb4<\/h3>\n\n- REPEATABLE READ \u3067\u306f\u3001\u666e\u901a\u306e
SELECT<\/code> \u306f\u6700\u521d\u306b\u8aad\u3093\u3060\u6642\u70b9\u306e\u30b9\u30ca\u30c3\u30d7\u30b7\u30e7\u30c3\u30c8\u3092\u898b\u307e\u3059<\/li>\nUPDATE<\/code> \/ DELETE<\/code> \/ SELECT ... FOR UPDATE<\/code> \u306a\u3069\u306f\u6700\u65b0\u306e\u30b3\u30df\u30c3\u30c8\u6e08\u307f\u30c7\u30fc\u30bf<\/strong>\u306b\u5bfe\u3057\u3066\u52d5\u304d\u307e\u3059\u3002\u305d\u306e\u305f\u3081\u300cSELECT \u3067\u306f\u898b\u3048\u306a\u304b\u3063\u305f\u884c\u304c UPDATE \u306e\u5bfe\u8c61\u306b\u306a\u308b\u300d\u3053\u3068\u304c\u3042\u308a\u3048\u307e\u3059<\/li>\n- \u30ed\u30c3\u30af\u3092\u53d6\u308b\u8aad\u307f\u53d6\u308a\u3067\u306f\u3001\u30cd\u30af\u30b9\u30c8\u30ad\u30fc\u30ed\u30c3\u30af\u304c\u7bc4\u56f2\u3078\u306e INSERT \u3092\u9632\u304e\u307e\u3059\u3002\u305d\u306e\u3076\u3093\u3001\u5f85\u3061\u3084\u30c7\u30c3\u30c9\u30ed\u30c3\u30af\u306f\u5897\u3048\u3084\u3059\u304f\u306a\u308a\u307e\u3059<\/li>\n
- \u30ed\u30b9\u30c8\u30a2\u30c3\u30d7\u30c7\u30fc\u30c8\u3092\u81ea\u52d5\u3067\u306f\u30a8\u30e9\u30fc\u306b\u3057\u307e\u305b\u3093\u3002\u5f8c\u304b\u3089\u66f4\u65b0\u3057\u305f\u5074\u306f\u3001\u5f85\u3063\u305f\u3042\u3068\u305d\u306e\u307e\u307e\u4e0a\u66f8\u304d\u3057\u307e\u3059<\/li>\n
- SERIALIZABLE \u3067\u306f\u3001autocommit \u304c\u7121\u52b9\u306a\u3068\u304d\u3001\u666e\u901a\u306e
SELECT<\/code> \u304c\u6697\u9ed9\u306b SELECT ... FOR SHARE<\/code> \u3068\u3057\u3066\u6271\u308f\u308c\u307e\u3059<\/li>\n<\/ul>\n\u540c\u3058\u300cREPEATABLE READ\u300d\u3067\u3082\u3001PostgreSQL \u3068 MySQL \u3067\u306f\u9632\u3044\u3067\u304f\u308c\u308b\u73fe\u8c61\u304c\u9055\u3046<\/strong>\u70b9\u306b\u6ce8\u610f\u3057\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n\u8a2d\u5b9a\u306e\u78ba\u8a8d\u3068\u6307\u5b9a<\/h2>\n-- PostgreSQL\nSHOW default_transaction_isolation;\nSHOW transaction_isolation;\nBEGIN ISOLATION LEVEL REPEATABLE READ;\n\n-- MySQL 8.0\nSELECT @@global.transaction_isolation, @@session.transaction_isolation;\nSET TRANSACTION ISOLATION LEVEL READ COMMITTED; -- \u6b21\u306e\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u306e\u307f\nSET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED; -- \u30bb\u30c3\u30b7\u30e7\u30f3\u5168\u4f53<\/pre>\n2\u30bb\u30c3\u30b7\u30e7\u30f3\u3067\u6319\u52d5\u3092\u78ba\u304b\u3081\u308b<\/h2>\nCREATE TABLE accounts (id int PRIMARY KEY, balance int NOT NULL);\nINSERT INTO accounts VALUES (1, 1000), (2, 1000);<\/pre>\n\u30ce\u30f3\u30ea\u30d4\u30fc\u30bf\u30d6\u30eb\u30ea\u30fc\u30c9\uff08PostgreSQL\uff09<\/h3>\n \n\n\n| \u624b\u9806<\/th>\n | \u30bb\u30c3\u30b7\u30e7\u30f3A<\/th>\n | \u30bb\u30c3\u30b7\u30e7\u30f3B<\/th>\n<\/tr>\n<\/thead>\n | \n\n| 1<\/td>\n | BEGIN ISOLATION LEVEL READ COMMITTED;<\/code><\/td>\n| <\/td>\n<\/tr>\n | \n| 2<\/td>\n | SELECT balance FROM accounts WHERE id = 1;<\/code> \u2192 1000<\/td>\n| <\/td>\n<\/tr>\n | \n| 3<\/td>\n | <\/td>\n | UPDATE accounts SET balance = 500 WHERE id = 1;<\/code><\/td>\n<\/tr>\n\n| 4<\/td>\n | SELECT balance FROM accounts WHERE id = 1;<\/code><\/td>\n| <\/td>\n<\/tr>\n | \n| 5<\/td>\n | COMMIT;<\/code><\/td>\n| <\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n READ COMMITTED \u3067\u306f\u3001\u624b\u98064\u3067 500 \u304c\u898b\u3048\u307e\u3059\u3002REPEATABLE READ \u306b\u3059\u308b\u3068 1000 \u306e\u307e\u307e\u3067\u3059\u3002<\/p>\n \u30ed\u30b9\u30c8\u30a2\u30c3\u30d7\u30c7\u30fc\u30c8\u306e\u691c\u51fa\uff08PostgreSQL \u306e REPEATABLE READ\uff09<\/h3>\n\n\n\n| \u624b\u9806<\/th>\n | \u30bb\u30c3\u30b7\u30e7\u30f3A<\/th>\n | \u30bb\u30c3\u30b7\u30e7\u30f3B<\/th>\n<\/tr>\n<\/thead>\n | \n\n| 1<\/td>\n | BEGIN ISOLATION LEVEL REPEATABLE READ;<\/code><\/td>\n| \u540c\u5de6<\/td>\n<\/tr>\n | \n| 2<\/td>\n | SELECT balance FROM accounts WHERE id = 1;<\/code><\/td>\n| \u540c\u5de6<\/td>\n<\/tr>\n | \n| 3<\/td>\n | UPDATE accounts SET balance = 900 WHERE id = 1;<\/code><\/td>\n| <\/td>\n<\/tr>\n | \n| 4<\/td>\n | <\/td>\n | UPDATE accounts SET balance = 800 WHERE id = 1;<\/code>\uff08\u5f85\u3061\u306b\u306a\u308b\uff09<\/td>\n<\/tr>\n\n| 5<\/td>\n | COMMIT;<\/code><\/td>\n| <\/td>\n<\/tr>\n | \n| 6<\/td>\n | <\/td>\n | could not serialize access due to concurrent update<\/code><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\nREAD COMMITTED \u3084 MySQL \u306e\u30c7\u30d5\u30a9\u30eb\u30c8\u3067\u306f\u3001B \u306e UPDATE \u306f\u5f85\u3063\u305f\u3042\u3068\u6210\u529f\u3057\u3001\u6700\u7d42\u5024\u306f 800 \u306b\u306a\u308a\u307e\u3059\uff08\u30ed\u30b9\u30c8\u30a2\u30c3\u30d7\u30c7\u30fc\u30c8\uff09\u3002<\/p>\n \u66f8\u304d\u8fbc\u307f\u30b9\u30ad\u30e5\u30fc<\/h3>\nCREATE TABLE on_call (staff_id int PRIMARY KEY, on_duty boolean NOT NULL);\nINSERT INTO on_call VALUES (1, true), (2, true);<\/pre>\n \n\n\n| \u624b\u9806<\/th>\n | \u30bb\u30c3\u30b7\u30e7\u30f3A<\/th>\n | \u30bb\u30c3\u30b7\u30e7\u30f3B<\/th>\n<\/tr>\n<\/thead>\n | \n\n| 1<\/td>\n | BEGIN ISOLATION LEVEL REPEATABLE READ;<\/code><\/td>\n| \u540c\u5de6<\/td>\n<\/tr>\n | \n| 2<\/td>\n | SELECT count(*) FROM on_call WHERE on_duty;<\/code> \u2192 2<\/td>\n| \u540c\u5de6 \u2192 2<\/td>\n<\/tr>\n | \n| 3<\/td>\n | UPDATE on_call SET on_duty = false WHERE staff_id = 1;<\/code><\/td>\n... WHERE staff_id = 2;<\/code><\/td>\n<\/tr>\n\n| 4<\/td>\n | COMMIT;<\/code><\/td>\nCOMMIT;<\/code><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\nPostgreSQL \u306e REPEATABLE READ \u3067\u306f\u3001\u4e21\u65b9\u30b3\u30df\u30c3\u30c8\u3055\u308c\u3066\u5f53\u756a\u304c0\u4eba\u306b\u306a\u308a\u307e\u3059\u3002SERIALIZABLE \u306b\u3059\u308b\u3068\u3001\u3069\u3061\u3089\u304b\u4e00\u65b9\u304c 40001<\/code> \u3067\u5931\u6557\u3057\u307e\u3059\u3002<\/p>\n\u203b \u624b\u9806\u306e\u7d50\u679c\u306f\u3001\u5404 DB \u306e\u516c\u5f0f\u30c9\u30ad\u30e5\u30e1\u30f3\u30c8\u306b\u66f8\u304b\u308c\u3066\u3044\u308b\u6319\u52d5\u306b\u57fa\u3065\u304f\u60f3\u5b9a\u3067\u3059\u3002\u624b\u5143\u306e\u74b0\u5883\u3067\u5b9f\u969b\u306b\u78ba\u304b\u3081\u3066\u304b\u3089\u5224\u65ad\u3057\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n \u9078\u3073\u65b9<\/h2>\n\u300c\u3069\u306e\u30ec\u30d9\u30eb\u304c\u6700\u5f37\u304b\u300d\u3067\u306f\u306a\u304f\u3001\u5b88\u308a\u305f\u3044\u6574\u5408\u6027\u306e\u7a2e\u985e\u306b\u5408\u308f\u305b\u3066\u9053\u5177\u3092\u9078\u3076<\/strong>\u306e\u304c\u30dd\u30a4\u30f3\u30c8\u3067\u3059\u3002<\/p>\n\n- \u307e\u305a\u30c7\u30d5\u30a9\u30eb\u30c8\u306e\u6319\u52d5\u3092\u77e5\u308b<\/strong>\uff1a\u4f7f\u3063\u3066\u3044\u308b DB \u306e\u30c7\u30d5\u30a9\u30eb\u30c8\u3068\u6319\u52d5\u3092\u628a\u63e1\u3057\u3001ORM \u3084\u30d5\u30ec\u30fc\u30e0\u30ef\u30fc\u30af\u306e\u8a2d\u5b9a\u3082\u78ba\u8a8d\u3057\u307e\u3059<\/li>\n
- \u5358\u4e00\u884c\u306e\u7af6\u5408\u306f\u5206\u96e2\u30ec\u30d9\u30eb\u4ee5\u5916\u3067\u89e3\u6c7a\u3059\u308b<\/strong>\uff1a\u30a2\u30c8\u30df\u30c3\u30af UPDATE\u3001
SELECT ... FOR UPDATE<\/code>\u3001\u697d\u89b3\u30ed\u30c3\u30af\u3092\u4f7f\u3044\u307e\u3059<\/li>\n- \u4e00\u8cab\u3057\u305f\u8aad\u307f\u53d6\u308a\u306b\u306f REPEATABLE READ<\/strong>\uff1a\u96c6\u8a08\u3084\u30a8\u30af\u30b9\u30dd\u30fc\u30c8\u306a\u3069\u3001\u8907\u6570\u306e\u30af\u30a8\u30ea\u3067\u540c\u3058\u6642\u70b9\u306e\u30c7\u30fc\u30bf\u3092\u898b\u305f\u3044\u5834\u5408\u306b\u4f7f\u3044\u307e\u3059<\/li>\n
- \u8907\u6570\u884c\u306b\u307e\u305f\u304c\u308b\u30eb\u30fc\u30eb\u306f SERIALIZABLE \uff0b \u30ea\u30c8\u30e9\u30a4<\/strong>\uff1a\u307e\u305f\u306f\u660e\u793a\u30ed\u30c3\u30af\u3084\u5236\u7d04\u3067\u5b88\u308a\u307e\u3059\u3002\u5236\u7d04\u3067\u8868\u73fe\u3067\u304d\u308b\u306a\u3089\u3001\u305d\u308c\u304c\u6700\u3082\u78ba\u5b9f\u3067\u3059<\/li>\n
- READ UNCOMMITTED \u306f\u57fa\u672c\u7684\u306b\u4f7f\u308f\u306a\u3044<\/strong><\/li>\n<\/ol>\n
MySQL \u3067\u30ae\u30e3\u30c3\u30d7\u30ed\u30c3\u30af\u306b\u3088\u308b\u5f85\u3061\u3084\u30c7\u30c3\u30c9\u30ed\u30c3\u30af\u306b\u60a9\u3093\u3067\u3044\u308b\u5834\u5408\u306f\u3001READ COMMITTED \u3082\u9078\u629e\u80a2\u306b\u306a\u308a\u307e\u3059\u3002\u305f\u3060\u3057\u884c\u30d9\u30fc\u30b9\u306e\u30d0\u30a4\u30ca\u30ea\u30ed\u30b0\uff08MySQL 8.0 \u306e\u30c7\u30d5\u30a9\u30eb\u30c8\uff09\u304c\u524d\u63d0\u3067\u3001\u65e2\u5b58\u306e\u51e6\u7406\u3078\u306e\u5f71\u97ff\u306e\u691c\u8a3c\u3082\u5fc5\u8981\u3067\u3059\u3002<\/p>\n \n\n\n| \u3084\u308a\u305f\u3044\u3053\u3068<\/th>\n | \u304a\u3059\u3059\u3081<\/th>\n<\/tr>\n<\/thead>\n | \n\n| \u5358\u4e00\u884c\u306e\u52a0\u6e1b\u7b97\u30fb\u5728\u5eab\u5f15\u304d\u5f53\u3066<\/td>\n | \u30a2\u30c8\u30df\u30c3\u30af UPDATE \/ FOR UPDATE<\/code> \/ \u697d\u89b3\u30ed\u30c3\u30af<\/td>\n<\/tr>\n\n| \u8907\u6570\u30af\u30a8\u30ea\u3067\u6570\u5b57\u3092\u63c3\u3048\u305f\u3044\u96c6\u8a08<\/td>\n | REPEATABLE READ\uff08READ ONLY\uff09<\/td>\n<\/tr>\n | \n| \u8907\u6570\u884c\u306b\u307e\u305f\u304c\u308b\u30eb\u30fc\u30eb\u306e\u7dad\u6301<\/td>\n | SERIALIZABLE \uff0b \u30ea\u30c8\u30e9\u30a4\u3001\u307e\u305f\u306f\u660e\u793a\u30ed\u30c3\u30af\u30fb\u5236\u7d04<\/td>\n<\/tr>\n | \n| \u4e00\u822c\u7684\u306a Web \u30a2\u30d7\u30ea\u306e CRUD<\/td>\n | DB \u306e\u30c7\u30d5\u30a9\u30eb\u30c8 \uff0b \u4e0a\u8a18\u30d1\u30bf\u30fc\u30f3\u306e\u4f7f\u3044\u5206\u3051<\/td>\n<\/tr>\n | \n| \u30b3\u30df\u30c3\u30c8\u3055\u308c\u3066\u3044\u306a\u3044\u30c7\u30fc\u30bf\u3092\u8aad\u307f\u305f\u3044<\/td>\n | \u307b\u307c\u4e0d\u8981<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n-- \u96c6\u8a08\u7528\uff08PostgreSQL\uff09\nBEGIN ISOLATION LEVEL REPEATABLE READ READ ONLY;\n-- \u96c6\u8a08\u7528\uff08MySQL\uff09\nSTART TRANSACTION WITH CONSISTENT SNAPSHOT, READ ONLY;<\/pre>\n\u5b9f\u88c5\u4f8b<\/h2>\n\u30a2\u30c8\u30df\u30c3\u30af\u306a UPDATE<\/h3>\nUPDATE accounts\nSET balance = balance - 100\nWHERE id = 1\nAND balance >= 100;\n-- \u66f4\u65b0\u4ef6\u6570\u304c 0 \u306a\u3089\u6b8b\u9ad8\u4e0d\u8db3\u3068\u3057\u3066\u6271\u3046<\/pre>\n\u697d\u89b3\u30ed\u30c3\u30af\uff08version \u5217\uff09<\/h3>\nUPDATE items\nSET stock = stock - 1,\n version = version + 1\nWHERE id = 42\nAND version = 7;\n-- \u66f4\u65b0\u4ef6\u6570\u304c 0 \u306a\u3089\u4ed6\u8005\u304c\u5148\u306b\u66f4\u65b0 \u2192 \u8aad\u307f\u76f4\u3057\u3066\u3084\u308a\u76f4\u3059<\/pre>\nSERIALIZABLE \u306e\u30ea\u30c8\u30e9\u30a4\uff08Python \/ psycopg 3\uff09<\/h3>\nimport time\n\nimport psycopg\nfrom psycopg import errors\n\nRETRYABLE = (errors.SerializationFailure, errors.DeadlockDetected)\n\n\ndef run_serializable(conn: psycopg.Connection, work, max_retries: int = 5):\n \"\"\"work(conn) \u3092 SERIALIZABLE \u3067\u5b9f\u884c\u3057\u3001\u76f4\u5217\u5316\u5931\u6557\u6642\u306f\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u3054\u3068\u30ea\u30c8\u30e9\u30a4\u3059\u308b\"\"\"\n for attempt in range(max_retries):\n try:\n with conn.transaction():\n conn.execute(\"SET TRANSACTION ISOLATION LEVEL SERIALIZABLE\")\n return work(conn)\n except RETRYABLE:\n time.sleep(0.05 * (2 ** attempt)) # \u6307\u6570\u30d0\u30c3\u30af\u30aa\u30d5\n raise RuntimeError(\"serialization retry limit exceeded\")\n\n\ndef take_off_duty(conn: psycopg.Connection, staff_id: int) -> None:\n on_duty = conn.execute(\n \"SELECT count(*) FROM on_call WHERE on_duty\"\n ).fetchone()[0]\n if on_duty <= 1:\n raise ValueError(\"\u5f53\u756a\u304c0\u4eba\u306b\u306a\u308b\u305f\u3081\u5916\u305b\u307e\u305b\u3093\")\n conn.execute(\n \"UPDATE on_call SET on_duty = false WHERE staff_id = %s\", (staff_id,)\n )\n\n\nwith psycopg.connect(\"dbname=example\", autocommit=True) as conn:\n run_serializable(conn, lambda c: take_off_duty(c, 1))<\/pre>\n \n- \u30ea\u30c8\u30e9\u30a4\u306f\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u5168\u4f53<\/strong>\u3092\u3084\u308a\u76f4\u3057\u307e\u3059<\/li>\n
work<\/code> \u306e\u4e2d\u3067\u3001\u5916\u90e8 API \u547c\u3073\u51fa\u3057\u3084\u30e1\u30fc\u30eb\u9001\u4fe1\u306e\u3088\u3046\u306a\u3084\u308a\u76f4\u305b\u306a\u3044\u526f\u4f5c\u7528\u3092\u8d77\u3053\u3055\u306a\u3044<\/strong>\u3088\u3046\u306b\u3057\u307e\u3059<\/li>\n- \u30ea\u30c8\u30e9\u30a4\u306e\u56de\u6570\u306b\u306f\u4e0a\u9650\u3092\u8a2d\u3051\u3001\u9593\u9694\u3092\u5c11\u3057\u305a\u3064\u5e83\u3052\u307e\u3059<\/li>\n<\/ul>\n
\u6ce8\u610f\u70b9<\/h2>\n\n- \u9577\u3044\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u3092\u907f\u3051\u308b<\/strong>\uff1aPostgreSQL \u3067\u306f VACUUM \u3092\u59a8\u3052\u3001MySQL \u3067\u306f undo \u30ed\u30b0\u3092\u81a8\u3089\u307e\u305b\u307e\u3059<\/li>\n
- \u30b3\u30cd\u30af\u30b7\u30e7\u30f3\u30d7\u30fc\u30eb<\/strong>\uff1a
SET SESSION<\/code> \u3067\u5909\u3048\u305f\u8a2d\u5b9a\u306f\u3001\u4f7f\u3044\u56de\u3055\u308c\u308b\u63a5\u7d9a\u306b\u6b8b\u308a\u307e\u3059\u3002\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u5358\u4f4d\u3067\u6307\u5b9a\u3059\u308b\u307b\u3046\u304c\u5b89\u5168\u3067\u3059<\/li>\n- ORM \u306e\u8a2d\u5b9a<\/strong>\uff1a\u30a2\u30d7\u30ea\u5074\u306e\u8a2d\u5b9a\u3067\u3001DB \u306e\u30c7\u30d5\u30a9\u30eb\u30c8\u304c\u4e0a\u66f8\u304d\u3055\u308c\u3066\u3044\u308b\u3053\u3068\u304c\u3042\u308a\u307e\u3059<\/li>\n
- \u30c6\u30b9\u30c8<\/strong>\uff1a\u5206\u96e2\u30ec\u30d9\u30eb\u304c\u539f\u56e0\u306e\u30d0\u30b0\u306f\u3001\u4e26\u884c\u5b9f\u884c\u3057\u306a\u3044\u3068\u518d\u73fe\u3057\u307e\u305b\u3093<\/li>\n
- DB \u306e\u79fb\u884c<\/strong>\uff1a\u540c\u3058\u540d\u524d\u306e\u30ec\u30d9\u30eb\u3067\u3082\u3001\u610f\u5473\u304c\u9055\u3046\u3053\u3068\u304c\u3042\u308a\u307e\u3059<\/li>\n<\/ul>\n
\u307e\u3068\u3081<\/h2>\n\n- \u5206\u96e2\u30ec\u30d9\u30eb\u306f\u300c\u540c\u6642\u5b9f\u884c\u4e2d\u306e\u4ed6\u8005\u306e\u5909\u66f4\u304c\u3069\u3053\u307e\u3067\u898b\u3048\u308b\u304b\u300d\u306e\u53d6\u308a\u6c7a\u3081<\/li>\n
- \u30c7\u30d5\u30a9\u30eb\u30c8\u306f PostgreSQL \u304c READ COMMITTED\u3001MySQL \u304c REPEATABLE READ\u3002\u540c\u3058\u540d\u524d\u306e\u30ec\u30d9\u30eb\u3067\u3082\u6319\u52d5\u306f DB \u3054\u3068\u306b\u9055\u3046<\/li>\n
- \u5b9f\u52d9\u3067\u52b9\u304f\u306e\u306f\u30ed\u30b9\u30c8\u30a2\u30c3\u30d7\u30c7\u30fc\u30c8\u3068\u66f8\u304d\u8fbc\u307f\u30b9\u30ad\u30e5\u30fc<\/li>\n
- \u5358\u4e00\u884c\u306e\u7af6\u5408\u306f\u30a2\u30c8\u30df\u30c3\u30af UPDATE\u30fb\u30ed\u30c3\u30af\u30fb\u697d\u89b3\u30ed\u30c3\u30af\u3067\u3001\u4e00\u8cab\u3057\u305f\u8aad\u307f\u53d6\u308a\u306f REPEATABLE READ \u3067\u3001\u8907\u6570\u884c\u306e\u30eb\u30fc\u30eb\u306f SERIALIZABLE \uff0b \u30ea\u30c8\u30e9\u30a4\uff08\u307e\u305f\u306f\u5236\u7d04\u30fb\u660e\u793a\u30ed\u30c3\u30af\uff09\u3067\u5b88\u308b<\/li>\n
- \u300c\u4e0a\u3052\u308c\u3070\u5b89\u5168\u300d\u3067\u306f\u306a\u304f\u3001\u5b88\u308a\u305f\u3044\u6574\u5408\u6027\u306b\u5408\u308f\u305b\u3066\u9078\u3076<\/strong><\/li>\n<\/ul>\n
\u53c2\u8003<\/h2>\n\n- PostgreSQL Documentation: Transaction Isolation<\/li>\n
- MySQL 8.0 Reference Manual: Transaction Isolation Levels \/ Consistent Nonlocking Reads \/ Locking Reads<\/li>\n
- Berenson et al., \"A Critique of ANSI SQL Isolation Levels\" (1995)<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"
\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u5206\u96e2\u30ec\u30d9\u30eb\uff08Isolation Level\uff09\u306f\u3001\u540c\u6642\u306b\u52d5\u3044\u3066\u3044\u308b\u30c8\u30e9\u30f3\u30b6\u30af\u30b7\u30e7\u30f3\u540c\u58eb\u304c\u3001\u76f8\u624b\u306e\u5909\u66f4\u3092\u3069\u3053\u307e\u3067\u898b\u3066\u3088\u3044\u304b\u3092\u6c7a\u3081\u308b\u8a2d\u5b9a\u3067\u3059\u3002<\/p>\n","protected":false},"author":1,"featured_media":3832,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"sns_share_botton_hide":"","vkExUnit_sns_title":"","_vk_print_noindex":"","sitemap_hide":"","_veu_custom_css":"","veu_display_promotion_alert":"","vkexunit_cta_each_option":"","_lightning_design_setting":[],"_jetpack_hide_featured_image":false,"_jetpack_featured_image_duplicate_dismissed":0,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[35],"tags":[99,1198,918,588,231,424,410,106,1162,708],"class_list":["post-3833","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-mysql-memorandum","tag-mysql","tag-postgresql","tag-read","tag-transaction","tag-231","tag-424","tag-410","tag-106","tag-1162","tag-708"],"veu_head_title_object":{"title":"","add_site_title":""},"jetpack_publicize_connections":[],"jetpack-related-posts":[],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"https:\/\/qol-kk.com\/wp2\/wp-content\/uploads\/2026\/11\/20261114-plan097-thumbnail.jpg","_links":{"self":[{"href":"https:\/\/qol-kk.com\/wp2\/wp-json\/wp\/v2\/posts\/3833","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/qol-kk.com\/wp2\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/qol-kk.com\/wp2\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/qol-kk.com\/wp2\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/qol-kk.com\/wp2\/wp-json\/wp\/v2\/comments?post=3833"}],"version-history":[{"count":1,"href":"https:\/\/qol-kk.com\/wp2\/wp-json\/wp\/v2\/posts\/3833\/revisions"}],"predecessor-version":[{"id":3836,"href":"https:\/\/qol-kk.com\/wp2\/wp-json\/wp\/v2\/posts\/3833\/revisions\/3836"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/qol-kk.com\/wp2\/wp-json\/wp\/v2\/media\/3832"}],"wp:attachment":[{"href":"https:\/\/qol-kk.com\/wp2\/wp-json\/wp\/v2\/media?parent=3833"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/qol-kk.com\/wp2\/wp-json\/wp\/v2\/categories?post=3833"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/qol-kk.com\/wp2\/wp-json\/wp\/v2\/tags?post=3833"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}} | | | | | | | | | | | | | | | | | | | | | |