oracle中关于clob类型字段的查询效率问题
今天，公司项目某个模块的导出报如下错误：
HTTP Status 500 – Internal Server Error
Type Exception Report Message Handler dispatch failed; nested exception is java.lang.OutOfMemoryError: GC overhead limit exceeded Description The server encountered an unexpected condition that prevented it from fulfilling the request. Exception org.springframework.web.util.NestedServletException: Handler dispatch failed; nested exception is java.lang.OutOfMemoryError: GC overhead limit exceeded
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1006)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:978)
org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:881)
javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:855)
javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61)
org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108)
org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137)
org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66)
org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449)
org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365)
org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90)
org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83)
org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:387)
org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362)
org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:357)
org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:270)
com.thetransactioncompany.cors.CORSFilter.doFilter(CORSFilter.java:209)
com.thetransactioncompany.cors.CORSFilter.doFilter(CORSFilter.java:244)
org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
Root Cause java.lang.OutOfMemoryError: GC overhead limit exceeded
java.util.Arrays.copyOf(Arrays.java:3332)
java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:124)
java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:448)
java.lang.StringBuilder.append(StringBuilder.java:136)
org.apache.ibatis.executor.resultset.ResultSetWrapper.getMapKey(ResultSetWrapper.java:176)
org.apache.ibatis.executor.resultset.ResultSetWrapper.getMappedColumnNames(ResultSetWrapper.java:158)
org.apache.ibatis.executor.resultset.DefaultResultSetHandler.applyPropertyMappings(DefaultResultSetHandler.java:428)
org.apache.ibatis.executor.resultset.DefaultResultSetHandler.getRowValue(DefaultResultSetHandler.java:916)
org.apache.ibatis.executor.resultset.DefaultResultSetHandler.applyNestedResultMappings(DefaultResultSetHandler.java:963)
org.apache.ibatis.executor.resultset.DefaultResultSetHandler.getRowValue(DefaultResultSetHandler.java:918)
org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValuesForNestedResultMap(DefaultResultSetHandler.java:881)
org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValues(DefaultResultSetHandler.java:328)
org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSet(DefaultResultSetHandler.java:303)
org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSets(DefaultResultSetHandler.java:196)
org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:64)
org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79)
sun.reflect.GeneratedMethodAccessor370.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:498)
org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:63)
com.sun.proxy.$Proxy1141.query(Unknown Source)
org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63)
org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:326)
org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)
org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83)
sun.reflect.GeneratedMethodAccessor369.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:498)
org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:63)
com.sun.proxy.$Proxy1140.query(Unknown Source)
org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)
org.springframework.remoting.support.RemoteInvocationUtils.fillInClientStackTraceIfPossible(RemoteInvocationUtils.java:45)
org.springframework.remoting.support.RemoteInvocationResult.recreate(RemoteInvocationResult.java:156)
org.springframework.remoting.support.RemoteInvocationBasedAccessor.recreateRemoteInvocationResult(RemoteInvocationBasedAccessor.java:85)
org.springframework.remoting.httpinvoker.HttpInvokerClientInterceptor.invoke(HttpInvokerClientInterceptor.java:162)
org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
com.sun.proxy.$Proxy765.listInvoiceDetail(Unknown Source)
com.csw.purchase.controller.InvoiceQueryController.exportAll(InvoiceQueryController.java:174)
com.csw.purchase.controller.InvoiceQueryController$$FastClassBySpringCGLIB$$f1d52ef0.invoke(<generated>)
org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:747)
org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
org.apache.shiro.spring.security.interceptor.AopAllianceAnnotationsAuthorizingMethodInterceptor$1.proceed(AopAllianceAnnotationsAuthorizingMethodInterceptor.java:82)
org.apache.shiro.authz.aop.AuthorizingMethodInterceptor.invoke(AuthorizingMethodInterceptor.java:39)
org.apache.shiro.spring.security.interceptor.AopAllianceAnnotationsAuthorizingMethodInterceptor.invoke(AopAllianceAnnotationsAuthorizingMethodInterceptor.java:115)
org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:689)
com.csw.purchase.controller.InvoiceQueryController$$EnhancerBySpringCGLIB$$b3090726.exportAll(<generated>)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:498)
org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209)
org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:870)
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:776)
org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:978)
org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:881)
javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:855)
javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61)
org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108)
org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137)
org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66)
org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449)
org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365)
org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90)
org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83)
org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:387)
org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362)
org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:357)
org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:270)
com.thetransactioncompany.cors.CORSFilter.doFilter(CORSFilter.java:209)
com.thetransactioncompany.cors.CORSFilter.doFilter(CORSFilter.java:244)
org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
Note The full stack trace of the root cause is available in the server logs. Apache Tomcat/8.5.24
内存溢出，导出前需要查询的sql如下：
SELECT
pid.id,
pid.materials_id,
pid.invoice_id,
pid.inform_order_detail_id,
pid.unit_price,
pid.invoice_amt,
pid.remark,
pid.biz_status,
pid.version,
pid.is_deleted,
pid.create_user,
pid.gmt_create,
pid.create_user_id,
pid.modified_user,
pid.gmt_modified,
pid.materials_release_id,
m.id m_id,
m.item_id m_item_id,
m.code m_code,
m.unit m_unit,
m.name m_name,
m.short_code m_short_code,
m.primary_uom m_primary_uom,
m.key_component_flag m_key_component_flag,
m.materials_type m_materials_type,
m.classification m_classification,
m.is_examine m_is_examine,
m.item_status m_item_status,
m.is_examine_item m_is_examine_item,
m.purchase_type m_purchase_type,
m.gmt_modified m_gmt_modified,
m.modified_user m_modified_user,
iiod.id iiod_id,
iiod.invoice_inform_order_id iiod_invoice_inform_order_id,
iiod.materials_id iiod_materials_id,
iiod.invoice_qty iiod_invoice_qty,
iiod.unit_price iiod_unit_price,
iiod.dispense_num iiod_dispense_num,
iiod.package_deal_code iiod_package_deal_code,
iiod.current_differ_price iiod_current_differ_price,
i.id i_id,
i.code i_code,
i.supplier_id i_supplier_id,
i.invoice_val i_invoice_val,
i.old_code i_old_code,
i.invoice_tax_val i_invoice_tax_val,
i.tax_amount i_tax_amount,
i.vmi_type i_vmi_type,
i.invoice_abstract i_invoice_abstract,
i.general_ledger_date i_general_ledger_date,
i.input_time i_input_time,
i.is_hand_dispose i_is_hand_dispose,
i.invoice_status i_invoice_status,
i.organization_id i_organization_id,
i.invoice_type i_invoice_type,
s.id s_id,
s.name s_name,
s.code s_code,
s.short_code s_short_code,
s.TYPE s_type,
s.main_product s_main_product,
s.tax_reg_num s_tax_reg_num,
iio.id iio_id,
iio.code iio_code,
iio.end_date iio_end_date,
iio.department_id iio_department_id,
iio.supplier_id iio_supplier_id,
iio.drawer iio_drawer,
iio.vmi_type iio_vmi_type,
iio.invoice_audit_status iio_invoice_audit_status,
iio.organization_id iio_organization_id,
iio.inform_order_type iio_inform_order_type,
it.id it_id,
it.invoice_id it_invoice_id,
it.tax_rate it_tax_rate,
it.tax_amount it_tax_amount
FROM
p_invoice_detail pid
LEFT JOIN s_materials m ON pid.materials_id = m.id
LEFT JOIN p_invoice_inform_order_detail iiod ON pid.inform_order_detail_id = iiod.id
LEFT JOIN p_invoice_inform_order iio ON iiod.invoice_inform_order_id = iio.id
LEFT JOIN p_invoice i ON pid.invoice_id = i.id
LEFT JOIN p_invoice_tax it ON i.id = it.invoice_id
LEFT JOIN s_supplier s ON s.id = i.supplier_id
WHERE
i.is_deleted = 0
其中表p_invoice_detail 中大概34W条数据，p_invoice_inform_order_detail中大概14W条数据，其它表中数据不超1W条，于是博主各种折腾，建索引，调整连接顺序等，都不起作用，博主用的navicat，每次查询我的naviicat就罢工，报unknown internal error (A70529121901) bad allocation，没办法，只好一个表一个表的排除，最后发现，左连接p_invoice_inform_order_detail 表后就会出现上述问题，其它表都没事，于是博主单独查询这张表发现也很慢：
用了37.704s只查询出8300条记录（表中共有约14W条数据），但是同样的查询有34W条数据的表p_invoice_detail却用了12.640s就全部查询出来了，博主就奇怪了，于是一个字段一个字段的试，终于发现是表p_invoice_inform_order_detail中的dispose_num字段导致的，后来发现该字段为clob类型，问题定位就好说了，上网查询发现将clob字段转为string类型再查询出来会提高效率，于是照做：将最开始的iiod.dispense_num修改为dbms_lob.substr(iiod.dispense_num,dbms_lob.getlength(iiod.dispense_num),1) dispense_num：
SELECT
pid.id,
pid.materials_id,
pid.invoice_id,
pid.inform_order_detail_id,
pid.unit_price,
pid.invoice_amt,
pid.remark,
pid.biz_status,
pid.version,
pid.is_deleted,
pid.create_user,
pid.gmt_create,
pid.create_user_id,
pid.modified_user,
pid.gmt_modified,
pid.materials_release_id,
m.id m_id,
m.item_id m_item_id,
m.code m_code,
m.unit m_unit,
m.name m_name,
m.short_code m_short_code,
m.primary_uom m_primary_uom,
m.key_component_flag m_key_component_flag,
m.materials_type m_materials_type,
m.classification m_classification,
m.is_examine m_is_examine,
m.item_status m_item_status,
m.is_examine_item m_is_examine_item,
m.purchase_type m_purchase_type,
m.gmt_modified m_gmt_modified,
m.modified_user m_modified_user,
iiod.id iiod_id,
iiod.invoice_inform_order_id iiod_invoice_inform_order_id,
iiod.materials_id iiod_materials_id,
iiod.invoice_qty iiod_invoice_qty,
iiod.unit_price iiod_unit_price,
dbms_lob.substr(iiod.dispense_num,dbms_lob.getlength(iiod.dispense_num),1) dispense_num,
iiod.package_deal_code iiod_package_deal_code,
iiod.current_differ_price iiod_current_differ_price,
i.id i_id,
i.code i_code,
i.supplier_id i_supplier_id,
i.invoice_val i_invoice_val,
i.old_code i_old_code,
i.invoice_tax_val i_invoice_tax_val,
i.tax_amount i_tax_amount,
i.vmi_type i_vmi_type,
i.invoice_abstract i_invoice_abstract,
i.general_ledger_date i_general_ledger_date,
i.input_time i_input_time,
i.is_hand_dispose i_is_hand_dispose,
i.invoice_status i_invoice_status,
i.organization_id i_organization_id,
i.invoice_type i_invoice_type,
s.id s_id,
s.name s_name,
s.code s_code,
s.short_code s_short_code,
s.TYPE s_type,
s.main_product s_main_product,
s.tax_reg_num s_tax_reg_num,
iio.id iio_id,
iio.code iio_code,
iio.end_date iio_end_date,
iio.department_id iio_department_id,
iio.supplier_id iio_supplier_id,
iio.drawer iio_drawer,
iio.vmi_type iio_vmi_type,
iio.invoice_audit_status iio_invoice_audit_status,
iio.organization_id iio_organization_id,
iio.inform_order_type iio_inform_order_type,
it.id it_id,
it.invoice_id it_invoice_id,
it.tax_rate it_tax_rate,
it.tax_amount it_tax_amount
FROM
p_invoice_detail pid
LEFT JOIN s_materials m ON pid.materials_id = m.id
LEFT JOIN p_invoice_inform_order_detail iiod ON pid.inform_order_detail_id = iiod.id
LEFT JOIN p_invoice_inform_order iio ON iiod.invoice_inform_order_id = iio.id
LEFT JOIN p_invoice i ON pid.invoice_id = i.id
LEFT JOIN p_invoice_tax it ON i.id = it.invoice_id
LEFT JOIN s_supplier s ON s.id = i.supplier_id
WHERE
i.is_deleted = 0
修改后查询，发现还是很慢，于是将其它不需要的字段去掉，调整为：
SELECT
i.id,
i.gmt_create,
i.code,
i.invoice_tax_val,
m.code materials_code,
m.name materials_name,
s.code supplier_code,
s.name supplier_name,
pid.unit_price,
it.tax_rate,
i.tax_amount,
iiod.current_differ_price,
pid.invoice_amt,
i.invoice_val,
pid.unit_price * pid.invoice_amt total_money,
dbms_lob.substr(iiod.dispense_num,dbms_lob.getlength(iiod.dispense_num),1) dispense_num,
decode(i.invoice_type,'','供应商平台','','发票平台') FROM
p_invoice_detail pid
LEFT JOIN p_invoice i ON pid.invoice_id = i.id
LEFT JOIN s_materials m ON pid.materials_id = m.id
LEFT JOIN p_invoice_inform_order_detail iiod ON pid.inform_order_detail_id = iiod.id
LEFT JOIN p_invoice_inform_order iio ON iiod.invoice_inform_order_id = iio.id
LEFT JOIN p_invoice_tax it ON i.id = it.invoice_id
LEFT JOIN s_supplier s ON s.id = i.supplier_id
WHERE
i.is_deleted = 0
这次总算不报错了，虽然查询单速度还是有点慢，但还能接受：
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