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【DM版本】: DM8
【操作系统】：UnionTech OS Server 20 Euler (1000) 64bit
【CPU】: 鲲鹏
【问题描述】*：我的数据库是从MySql迁移过来的，项目连接数据库正常，运行执行SQL都正常。

但是有一个查询SQL很长，执行导致报错网络通信异常，堆栈如下图。

注：我尝试过把SQL简写就不报错，并且这个长SQL去DM工具里执行是正常的。所以我初步怀疑是SQL过长导致，我记得MySql一样有长SQL限制，但是可以设置max_allowed_packet参数解决。不知道达梦数据库有没有相关设置，或者其他原因导致的此问题。希望请大佬们给予指导，谢谢！

### Cause: dm.jdbc.driver.DMException: 网络通信异常
; SQL []; 网络通信异常; nested exception is dm.jdbc.driver.DMException: 网络通信异常
	at org.springframework.jdbc.support.SQLStateSQLExceptionTranslator.doTranslate(SQLStateSQLExceptionTranslator.java:105)
	at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:73)
	at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:82)
	at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:82)
	at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:73)
	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:446)
	at com.sun.proxy.$Proxy124.selectList(Unknown Source)
	at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:230)
	at com.baomidou.mybatisplus.core.override.PageMapperMethod.executeForMany(PageMapperMethod.java:173)
	at com.baomidou.mybatisplus.core.override.PageMapperMethod.execute(PageMapperMethod.java:86)
	at com.baomidou.mybatisplus.core.override.PageMapperProxy.invoke(PageMapperProxy.java:64)
	at com.sun.proxy.$Proxy1095.listPage(Unknown Source)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:333)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
	at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213)
	at com.sun.proxy.$Proxy1096.listPage(Unknown Source)
	...
Caused by: dm.jdbc.driver.DMException: 网络通信异常
	at dm.jdbc.driver.DBError.throwException(DBError.java:683)
	at dm.jdbc.c.a.a(DBAccess.java:764)
	at dm.jdbc.c.a.a(DBAccess.java:311)
	at dm.jdbc.c.a.a(DBAccess.java:401)
	at dm.jdbc.driver.DmdbPreparedStatement.executeInner(DmdbPreparedStatement.java:221)
	at dm.jdbc.driver.DmdbPreparedStatement.do_execute(DmdbPreparedStatement.java:310)
	at dm.jdbc.driver.DmdbPreparedStatement.execute(DmdbPreparedStatement.java:1630)
	at com.p6spy.engine.wrapper.PreparedStatementWrapper.execute(PreparedStatementWrapper.java:362)
	at com.alibaba.druid.filter.FilterChainImpl.preparedStatement_execute(FilterChainImpl.java:3051)
	at com.alibaba.druid.filter.FilterEventAdapter.preparedStatement_execute(FilterEventAdapter.java:440)
	at com.alibaba.druid.filter.FilterChainImpl.preparedStatement_execute(FilterChainImpl.java:3049)
	at com.alibaba.druid.proxy.jdbc.PreparedStatementProxyImpl.execute(PreparedStatementProxyImpl.java:167)
	at com.alibaba.druid.pool.DruidPooledPreparedStatement.execute(DruidPooledPreparedStatement.java:498)
	at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:63)
	at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79)
	at sun.reflect.GeneratedMethodAccessor184.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:63)
	at com.sun.proxy.$Proxy1212.query(Unknown Source)
	at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63)
	at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:326)
	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:136)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
	at sun.reflect.GeneratedMethodAccessor180.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433)
	... 94 common frames omitted
Caused by: java.io.EOFException: null
	at dm.jdbc.util.Buffer$Node.load(Buffer.java:1184)
	at dm.jdbc.util.Buffer$Node.access$6(Buffer.java:1164)
	at dm.jdbc.util.Buffer.load(Buffer.java:351)
	at dm.jdbc.c.a.c(DBAccess.java:855)
	at dm.jdbc.c.a.a(DBAccess.java:757)
	... 122 common frames omitted