我的Java应用程序通过MyBatis与PostgreSQL交互。
它从多个线程执行这个请求
select *
from v_packet_unread
limit 1000
for update skip locked
有时得到CCD_ 1。我记得这个错误发生在乐观更新的情况下，在这里我只使用SELECT，甚至没有使用update，并且不能解释发生了什么
v_packet_unread-是一个连接两个小表(每个表2列(的简单视图，没有任何隐藏效果(如函数调用的触发器(。
你能帮我找出这种行为的原因以及如何避免这种情况吗？
异常：
2021-07-16 06:31:39.278 [validator-exec-5 ] [ERROR] r.c.p.Operators - Operator called default onErrorDropped
reactor.core.Exceptions$ErrorCallbackNotImplemented: org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: org.postgresql.util.PSQLException: ERROR: could not serialize access due to concurrent update
### The error may exist in database/schemas/receiver/map/PacketMapper.xml
### The error may involve defaultParameterMap
### The error occurred while setting parameters
### SQL: select * from v_packet_unread limit ? for update skip locked
### Cause: org.postgresql.util.PSQLException: ERROR: could not serialize access due to concurrent update
Caused by: org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: org.postgresql.util.PSQLException: ERROR: could not serialize access due to concurrent update
### The error may exist in database/schemas/receiver/map/PacketMapper.xml
### The error may involve defaultParameterMap
### The error occurred while setting parameters
### SQL: select * from v_packet_unread limit ? for update skip locked
### Cause: org.postgresql.util.PSQLException: ERROR: could not serialize access due to concurrent update
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:153)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:145)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140)
at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:147)
at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:80)
at org.apache.ibatis.binding.MapperProxy$PlainMethodInvoker.invoke(MapperProxy.java:145)
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:86)
at jdk.proxy2/jdk.proxy2.$Proxy65.selectUnread(Unknown Source)
at ...
Caused by: org.postgresql.util.PSQLException: ERROR: could not serialize access due to concurrent update
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2553)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2285)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:323)
at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:481)
at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:401)
at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:164)
at org.postgresql.jdbc.PgPreparedStatement.execute(PgPreparedStatement.java:153)
at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:64)
at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79)
at org.apache.ibatis.executor.BatchExecutor.doQuery(BatchExecutor.java:92)
at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:325)
at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)
at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:89)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:151)
... 25 common frames omitted
版本：
PostgreSQL 12.5 on x86_64-redhat-linux-gnu,
compiled by gcc (GCC) 8.3.1 20191121 (Red Hat 8.3.1-5), 64-bit
dependencies:
org.mybatis:mybatis:3.5.7
org.postgresql:postgresql:42.2.20
如果您在隔离级别为REPEATABLE READ或更高的事务中运行，则可能会发生这种情况：如果您试图锁定自事务启动以来由其他事务同时修改的行，则会出现序列化错误。
要避免这种情况，请使用默认的READ COMMITTED隔离级别。