我正在调试使用JPA / Hibernate和Postgres（9.6.2）的Java应用程序的奇怪行为。
应用程序有3个实体：用户，国家/地区，用户事件。
Hibernate将其映射到4个表：用户，国家/地区，userevent，hibernate_sequences 。
用户实体具有版本列（ @Version ）和乐观锁定主题。 @GeneratedValue（strategy = GenerationType.TABLE ）的主键为＆＃34; id＆＃34; 。用户表将获得最多的读写次数（最受欢迎的表）。
我在运行Postgres日志时创建了几个压力测试以模拟高负载并注意到以下错误（请注意导致它的更新查询）：
ERROR: deadlock detected
DETAIL: Process 46758 waits for ShareLock on transaction 1580660; blocked by process 46759.
Process 46759 waits for AccessExclusiveLock on tuple (97,26) of relation 17353 of database 16385; blocked by process 46758.
Process 46758: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
Process 46759: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
HINT: See server log for query details.
CONTEXT: while updating tuple (97,26) in relation "users"
据我所知，Postgres有分享和排他性;行，表或索引级别锁。以错误的顺序在相同的对象上获取它们可能会导致死锁。
但对于这种特殊情况， 为什么我会遇到乐观锁定的死锁 ？在这种情况下，我希望一个事务成功，一个事务返回0 UPDATE。
表格，FK及其指数描述如下：
##################################################################################################
Table "public.users"
Column | Type | Modifiers | Storage | Stats target | Description
-------------------+-----------------------------+-----------+----------+--------------+-------------
id | bigint | not null | plain | |
confirmationstate | character varying(20) | not null | extended | |
created | timestamp without time zone | not null | plain | |
dateofbirth | date | not null | plain | |
email | character varying(255) | not null | extended | |
firstname | character varying(100) | not null | extended | |
gender | character varying(10) | not null | extended | |
lastname | character varying(100) | not null | extended | |
lastusedlocale | character varying(5) | | extended | |
middlename | character varying(100) | | extended | |
passwordhash | bytea | not null | extended | |
passwordsalt | bytea | not null | extended | |
phone | character varying(50) | | extended | |
role | character varying(50) | not null | extended | |
signinstate | character varying(20) | not null | extended | |
updated | timestamp without time zone | not null | plain | |
username | character varying(255) | | extended | |
version | bigint | | plain | |
country_iso | character varying(2) | | extended | |
Indexes:
"users_pkey" PRIMARY KEY, btree (id)
"email_idx" UNIQUE CONSTRAINT, btree (email)
"username_idx" UNIQUE CONSTRAINT, btree (username)
"firstname_idx" btree (firstname)
"lastname_idx" btree (lastname)
"phone_idx" btree (phone)
Foreign-key constraints:
"fk_ghgfskd1hgobolp0fh20i6h14" FOREIGN KEY (country_iso) REFERENCES countries(iso)
Referenced by:
TABLE "userevents" CONSTRAINT "fk_69tm2wh9hkakap0uyjw41c61h" FOREIGN KEY (targetuser_id) REFERENCES users(id)
TABLE "userevents" CONSTRAINT "fk_nov1tso5k93h4m88unjy4f2kl" FOREIGN KEY (user_id) REFERENCES users(id)
##################################################################################################
Table "public.countries"
Column | Type | Modifiers | Storage | Stats target | Description
------------+------------------------+-----------+----------+--------------+-------------
iso | character varying(2) | not null | extended | |
iso3 | character varying(3) | | extended | |
name | character varying(80) | | extended | |
nativename | character varying(150) | | extended | |
numcode | integer | | plain | |
phonecode | integer | not null | plain | |
Indexes:
"countries_pkey" PRIMARY KEY, btree (iso)
"iso3_idx" UNIQUE CONSTRAINT, btree (iso3)
"nativename_idx" btree (nativename)
Referenced by:
TABLE "users" CONSTRAINT "fk_ghgfskd1hgobolp0fh20i6h14" FOREIGN KEY (country_iso) REFERENCES countries(iso)
##################################################################################################
Table "public.userevents"
Column | Type | Modifiers | Storage | Stats target | Description
---------------+-----------------------------+-----------+----------+--------------+-------------
id | bigint | not null | plain | |
data | bytea | | extended | |
ip | character varying(255) | not null | extended | |
time | timestamp without time zone | not null | plain | |
type | character varying(15) | not null | extended | |
url | character varying(2000) | | extended | |
targetuser_id | bigint | | plain | |
user_id | bigint | not null | plain | |
Indexes:
"userevents_pkey" PRIMARY KEY, btree (id)
"usertypetime_idx" btree (user_id, type, "time")
Foreign-key constraints:
"fk_69tm2wh9hkakap0uyjw41c61h" FOREIGN KEY (targetuser_id) REFERENCES users(id)
"fk_nov1tso5k93h4m88unjy4f2kl" FOREIGN KEY (user_id) REFERENCES users(id)
##################################################################################################
Table "public.hibernate_sequences"
Column | Type | Modifiers | Storage | Stats target | Description
------------------------+------------------------+-----------+----------+--------------+-------------
sequence_name | character varying(255) | | extended | |
sequence_next_hi_value | integer | | plain | |
##################################################################################################
编辑1：
先生。 pozs 建议查看循环FK的现有问题，并提供有关事务中发生情况的更多详细信息。我在这个模式中没有循环FK，因此我在Postgres中设置了日志记录并尝试隔离问题。
以下是导致死锁的2个进程的所有语句的完整日志。
处理1 日志：
2017-04-11 12:41:31 PDT 73842 LOG: 00000: execute S_2: BEGIN
2017-04-11 12:41:31 PDT 73842 LOG: 00000: execute S_3: select user0_.id as id1_2_0_, user0_.confirmationState as confirma2_2_0_, user0_.country_iso as country19_2_0_, user0_.created as created3_2_0_, user0_.dateOfBirth as dateOfBi4_2_0_, user0_.email as email5_2_0_, user0_.firstName as firstNam6_2_0_, user0_.gender as gender7_2_0_, user0_.lastName as lastName8_2_0_, user0_.lastUsedLocale as lastUsed9_2_0_, user0_.middleName as middleN10_2_0_, user0_.passwordHash as passwor11_2_0_, user0_.passwordSalt as passwor12_2_0_, user0_.phone as phone13_2_0_, user0_.role as role14_2_0_, user0_.signInState as signInS15_2_0_, user0_.updated as updated16_2_0_, user0_.username as usernam17_2_0_, user0_.version as version18_2_0_, country1_.iso as iso1_0_1_, country1_.iso3 as iso2_0_1_, country1_.name as name3_0_1_, country1_.nativeName as nativeNa4_0_1_, country1_.numCode as numCode5_0_1_, country1_.phoneCode as phoneCod6_0_1_ from users user0_ left outer join countries country1_ on user0_.country_iso=country1_.iso where user0_.id=$1
2017-04-11 12:41:31 PDT 73842 DETAIL: parameters: $1 = '10'
2017-04-11 12:41:31 PDT 73842 LOG: 00000: execute S_10: select country0_.iso as iso1_0_, country0_.iso3 as iso2_0_, country0_.name as name3_0_, country0_.nativeName as nativeNa4_0_, country0_.numCode as numCode5_0_, country0_.phoneCode as phoneCod6_0_ from countries country0_ order by country0_.nativeName, country0_.name
2017-04-11 12:41:31 PDT 73842 LOG: 00000: execute S_4: insert into userEvents (data, ip, targetUser_id, time, type, url, user_id, id) values ($1, $2, $3, $4, $5, $6, $7, $8)
2017-04-11 12:41:31 PDT 73842 DETAIL: parameters: $1 = '\x04545...LONG_BINARY_DATA...d', $2 = '192.168.1.2', $3 = '10', $4 = '2017-04-11 19:41:31.268', $5 = 'UPDATE', $6 = 'http://example.org', $7 = '10', $8 = '201243'
2017-04-11 12:41:31 PDT 73842 LOG: 00000: execute S_7: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
2017-04-11 12:41:31 PDT 73842 DETAIL: parameters: $1 = 'CONFIRMED', $2 = 'IS', $3 = '1984-10-10', $4 = 'email-527785869@example.org', $5 = 's7w7j5cdm1bg', $6 = 'FEMALE', $7 = 'Terrier9', $8 = 'en', $9 = 'Russel', $10 = '\x64..6439', $11 = '\x33...3836', $12 = '+16509876945', $13 = 'USER', $14 = 'ENABLED', $15 = '2017-04-11 19:41:31.268', $16 = 'demouser9', $17 = '547', $18 = '10', $19 = '546'
2017-04-11 12:41:32 PDT 73842 LOG: 00000: process 73842 detected deadlock while waiting for ExclusiveLock on tuple (206,43) of relation 17992 of database 16385 after 1000.114 ms
2017-04-11 12:41:32 PDT 73842 DETAIL: Process holding the lock: 73817. Wait queue: .
2017-04-11 12:41:32 PDT 73842 LOCATION: ProcSleep, proc.c:1415
2017-04-11 12:41:32 PDT 73842 STATEMENT: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
2017-04-11 12:41:32 PDT 73842 ERROR: 40P01: deadlock detected
2017-04-11 12:41:32 PDT 73842 DETAIL: Process 73842 waits for ExclusiveLock on tuple (206,43) of relation 17992 of database 16385; blocked by process 73817.
Process 73817 waits for ShareLock on transaction 2716972; blocked by process 73842.
Process 73842: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
2017-04-11 12:41:32 PDT 73842 HINT: See server log for query details.
2017-04-11 12:41:32 PDT 73842 LOCATION: DeadLockReport, deadlock.c:1140
2017-04-11 12:41:32 PDT 73842 STATEMENT: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
2017-04-11 12:41:32 PDT 73842 ERROR: 25P02: current transaction is aborted, commands ignored until end of transaction block
2017-04-11 12:41:32 PDT 73842 LOCATION: exec_parse_message, postgres.c:1303
2017-04-11 12:41:32 PDT 73842 STATEMENT: SELECT NULL AS TABLE_CAT, n.nspname AS TABLE_SCHEM, c.relname AS TABLE_NAME, CASE n.nspname ~ '^pg_' OR n.nspname = 'information_schema' WHEN true THEN CASE WHEN n.nspname = 'pg_catalog' OR n.nspname = 'information_schema' THEN CASE c.relkind WHEN 'r' THEN 'SYSTEM TABLE' WHEN 'v' THEN 'SYSTEM VIEW' WHEN 'i' THEN 'SYSTEM INDEX' ELSE NULL END WHEN n.nspname = 'pg_toast' THEN CASE c.relkind WHEN 'r' THEN 'SYSTEM TOAST TABLE' WHEN 'i' THEN 'SYSTEM TOAST INDEX' ELSE NULL END ELSE CASE c.relkind WHEN 'r' THEN 'TEMPORARY TABLE' WHEN 'i' THEN 'TEMPORARY INDEX' WHEN 'S' THEN 'TEMPORARY SEQUENCE' WHEN 'v' THEN 'TEMPORARY VIEW' ELSE NULL END END WHEN false THEN CASE c.relkind WHEN 'r' THEN 'TABLE' WHEN 'i' THEN 'INDEX' WHEN 'S' THEN 'SEQUENCE' WHEN 'v' THEN 'VIEW' WHEN 'c' THEN 'TYPE' WHEN 'f' THEN 'FOREIGN TABLE' WHEN 'm' THEN 'MATERIALIZED VIEW' ELSE NULL END ELSE NULL END AS TABLE_TYPE, d.description AS REMARKS FROM pg_catalog.pg_namespace n, pg_catalog.pg_class c LEFT JOIN pg_catalog.pg_description d ON (c.oid = d.objoid AND d.objsubid = 0) LEFT JOIN pg_catalog.pg_class dc ON (d.classoid=dc.oid AND dc.relname='pg_class') LEFT JOIN pg_catalog.pg_namespace dn ON (dn.oid=dc.relnamespace AND dn.nspname='pg_catalog') WHERE c.relnamespace = n.oid AND c.relname LIKE 'PROBABLYNOT' AND (false OR ( c.relkind = 'r' AND n.nspname !~ '^pg_' AND n.nspname <> 'information_schema' ) ) ORDER BY TABLE_TYPE,TABLE_SCHEM,TABLE_NAME
2017-04-11 12:41:32 PDT 73842 LOG: 00000: execute S_11: ROLLBACK
处理2 日志：
2017-04-11 12:41:31 PDT 73817 LOG: 00000: execute S_2: BEGIN
2017-04-11 12:41:31 PDT 73817 LOG: 00000: execute S_3: select user0_.id as id1_2_0_, user0_.confirmationState as confirma2_2_0_, user0_.country_iso as country19_2_0_, user0_.created as created3_2_0_, user0_.dateOfBirth as dateOfBi4_2_0_, user0_.email as email5_2_0_, user0_.firstName as firstNam6_2_0_, user0_.gender as gender7_2_0_, user0_.lastName as lastName8_2_0_, user0_.lastUsedLocale as lastUsed9_2_0_, user0_.middleName as middleN10_2_0_, user0_.passwordHash as passwor11_2_0_, user0_.passwordSalt as passwor12_2_0_, user0_.phone as phone13_2_0_, user0_.role as role14_2_0_, user0_.signInState as signInS15_2_0_, user0_.updated as updated16_2_0_, user0_.username as usernam17_2_0_, user0_.version as version18_2_0_, country1_.iso as iso1_0_1_, country1_.iso3 as iso2_0_1_, country1_.name as name3_0_1_, country1_.nativeName as nativeNa4_0_1_, country1_.numCode as numCode5_0_1_, country1_.phoneCode as phoneCod6_0_1_ from users user0_ left outer join countries country1_ on user0_.country_iso=country1_.iso where user0_.id=$1
2017-04-11 12:41:31 PDT 73817 DETAIL: parameters: $1 = '10'
2017-04-11 12:41:31 PDT 73817 LOG: 00000: execute S_6: select country0_.iso as iso1_0_0_, country0_.iso3 as iso2_0_0_, country0_.name as name3_0_0_, country0_.nativeName as nativeNa4_0_0_, country0_.numCode as numCode5_0_0_, country0_.phoneCode as phoneCod6_0_0_ from countries country0_ where country0_.iso=$1
2017-04-11 12:41:31 PDT 73817 DETAIL: parameters: $1 = 'JP'
2017-04-11 12:41:31 PDT 73817
2017-04-11 12:41:31 PDT 73817 LOG: 00000: execute S_5: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
2017-04-11 12:41:31 PDT 73817 DETAIL: parameters: $1 = 'CONFIRMED', $2 = 'JP', $3 = '1984-10-10', $4 = 'email465994020@example.org', $5 = '-1kcg4facio48g', $6 = 'FEMALE', $7 = 'Terrier9', $8 = 'en', $9 = 'Russel', $10 = '\x64656d6f7573657270617373776f726439', $11 = '\x33...3836', $12 = '+16509876905', $13 = 'USER', $14 = 'ENABLED', $15 = '2017-04-11 19:41:31.188', $16 = 'demouser9', $17 = '547', $18 = '10', $19 = '546'
2017-04-11 12:41:32 PDT 73842 DETAIL: Process holding the lock: 73817. Wait queue: .
2017-04-11 12:41:32 PDT 73842 DETAIL: Process 73842 waits for ExclusiveLock on tuple (206,43) of relation 17992 of database 16385; blocked by process 73817.
Process 73817 waits for ShareLock on transaction 2716972; blocked by process 73842.
Process 73817: update users set confirmationState=$1, country_iso=$2, dateOfBirth=$3, email=$4, firstName=$5, gender=$6, lastName=$7, lastUsedLocale=$8, middleName=$9, passwordHash=$10, passwordSalt=$11, phone=$12, role=$13, signInState=$14, updated=$15, username=$16, version=$17 where id=$18 and version=$19
2017-04-11 12:41:32 PDT 73817 LOG: 00000: execute S_10: ROLLBACK
流程1的流程为：
流程2的流程为：
是否因为获取对INSK的唯一锁定（userEvents.user_id）进行INSERT 以及稍后对UPDATE进行独占锁定（users.id = 10） 第一个交易中的 （users.id = 10）以及第二个中的（userEvents.user_id） EM>？
因为 当我强迫＆＃34;更新用户＆＃34;之前＆＃34; INSERT INTO userEvents＆＃34; 在高负荷下我不会再看到死锁。
答案 0 :(得分：1)
如果两个事务试图同时使用相同的version更新同一行，则其中一个将获取该行的锁定，另一个将阻止。
只要第一笔交易处于有效状态，第二笔交易就无法决定是否已获得＆＃34;＆＃34;＆＃34;＆＃34;＆＃34;乐观的锁。如果第一个事务成功，则第二个事务将发现version不再匹配，并且将返回而不更新任何内容。但是，如果第一个事务回滚，第二个事务将获取旧version上的锁并继续更新。
与此同时，它只需要等待，一旦你的事务等待，死锁场景就很容易构建。