[IBATISNET-206] groupBy incorrectly handles left outer join results where right part is empty

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: DataMapper 1.6
• Fix Version/s: DataMapper 1.6.1
• Component/s: DataMapper
• Assignee: Gilles Bayon
• Reporter: Ihar Bury
• Created: 12/Feb/07 13:45
• Updated: 15/Feb/07 19:51
• Resolved: 15/Feb/07 19:51

Description

We use the newly added groupBy functionality as follows:

<resultMap id="ConsumptionHistoryUsers" class="User" groupBy="Id">
<result property="Id" column="id" />
...
<result property="filteredTopContentConsumptionHistory" resultMapping="UserMap.ConsumptionHistoryUsersContent" />
</resultMap>
<resultMap id="ConsumptionHistoryUsersContent" class="Content">
<result property="Id" column="content_id" />
<result property="Creator" resultMapping="UserMap.ConsumptionHistoryUsersContentCreator" />
<result property="DateCreated" column="content_date_created" />
<result property="Title" column="content_title" />
<discriminator type="int" column="content_subtype_id" />
<subMap value="5" resultMapping="ConsumptionHistoryUsersBlog" />
</resultMap>
<resultMap id="ConsumptionHistoryUsersBlog" class="BlogContent" extends="UserMap.ConsumptionHistoryUsersContent">
</resultMap>

The result map is for select SQL like

select *
from User
left outer join Content on ...

This works well in the cases where each selected User has at least one Content joined to it. But when there is one User that doesn't have any corresponding content, a failure occurs. The record returned from the database has values for User and has null values for all Content columns. iBATIS should just store an empty collection to the resulting User object in this case but it tries to load all those nulls as a Content object. In our case that ends up with NullReferenceException while analizing the discriminator value.

subMap = _discriminator.GetSubMap( dataBaseValue.ToString() );

where dataBaseValue == null

> IBatisNet.DataMapper.dll!IBatisNet.DataMapper.Configuration.ResultMapping.ResultMap.ResolveSubMap(System.Data.IDataReader dataReader =

{IBatisNet.DataMapper.Commands.DataReaderDecorator}) Line 444 C#
IBatisNet.DataMapper.dll!IBatisNet.DataMapper.MappedStatements.PropertStrategy.GroupByStrategy.Get(IBatisNet.DataMapper.Scope.RequestScope request = {IBatisNet.DataMapper.Scope.RequestScope}, IBatisNet.DataMapper.Configuration.ResultMapping.IResultMap resultMap = {IBatisNet.DataMapper.Configuration.ResultMapping.ResultMap}, IBatisNet.DataMapper.Configuration.ResultMapping.ResultProperty mapping = {IBatisNet.DataMapper.Configuration.ResultMapping.ResultProperty}, ref object target = {Tw.Core.BusinessLayer.ObjectModel.Users.User}, System.Data.IDataReader reader = {IBatisNet.DataMapper.Commands.DataReaderDecorator}

) Line 99 + 0x19 bytes C#
IBatisNet.DataMapper.dll!IBatisNet.DataMapper.MappedStatements.PropertStrategy.GroupByStrategy.Set(IBatisNet.DataMapper.Scope.RequestScope request =

{IBatisNet.DataMapper.Scope.RequestScope}, IBatisNet.DataMapper.Configuration.ResultMapping.IResultMap resultMap = {IBatisNet.DataMapper.Configuration.ResultMapping.ResultMap}, IBatisNet.DataMapper.Configuration.ResultMapping.ResultProperty mapping = {IBatisNet.DataMapper.Configuration.ResultMapping.ResultProperty}, ref object target = {Tw.Core.BusinessLayer.ObjectModel.Users.User}, System.Data.IDataReader reader = {IBatisNet.DataMapper.Commands.DataReaderDecorator}, object keys = null) Line 71 + 0x15 bytes C#
IBatisNet.DataMapper.dll!IBatisNet.DataMapper.MappedStatements.ResultStrategy.GroupByStrategy.Process(IBatisNet.DataMapper.Scope.RequestScope request = {IBatisNet.DataMapper.Scope.RequestScope}

, ref System.Data.IDataReader reader =

{IBatisNet.DataMapper.Commands.DataReaderDecorator}, object resultObject = null) Line 88 + 0x2e bytes C#
IBatisNet.DataMapper.dll!IBatisNet.DataMapper.MappedStatements.ResultStrategy.MapStrategy.Process(IBatisNet.DataMapper.Scope.RequestScope request = {IBatisNet.DataMapper.Scope.RequestScope}, ref System.Data.IDataReader reader = {IBatisNet.DataMapper.Commands.DataReaderDecorator}

, object resultObject = null) Line 64 + 0x14 bytes C#
IBatisNet.DataMapper.dll!IBatisNet.DataMapper.MappedStatements.MappedStatement.RunQueryForList<Tw.Core.BusinessLayer.ObjectModel.Users.User>(IBatisNet.DataMapper.Scope.RequestScope request =

{IBatisNet.DataMapper.Scope.RequestScope}

, IBatisNet.DataMapper.ISqlMapSession session =

{IBatisNet.DataMapper.SqlMapSession}, object parameterObject = {Tw.Core.DataLayer.Mappers.Users.UserMapper.UserConsumptionHistoryUsersParams}, System.Collections.Generic.IList<Tw.Core.BusinessLayer.ObjectModel.Users.User> resultObject = null, IBatisNet.DataMapper.RowDelegate<Tw.Core.BusinessLayer.ObjectModel.Users.User> rowDelegate = null) Line 768 + 0x17 bytes C#
IBatisNet.DataMapper.dll!IBatisNet.DataMapper.MappedStatements.MappedStatement.ExecuteQueryForList<Tw.Core.BusinessLayer.ObjectModel.Users.User>(IBatisNet.DataMapper.ISqlMapSession session = {IBatisNet.DataMapper.SqlMapSession}

, object parameterObject =

{Tw.Core.DataLayer.Mappers.Users.UserMapper.UserConsumptionHistoryUsersParams}) Line 643 + 0x45 bytes C#
IBatisNet.DataMapper.dll!IBatisNet.DataMapper.SqlMapper.QueryForList<Tw.Core.BusinessLayer.ObjectModel.Users.User>(string statementName = "GetUserConsumptionHistoryUsers", object parameterObject = {Tw.Core.DataLayer.Mappers.Users.UserMapper.UserConsumptionHistoryUsersParams}

) Line 1019 + 0x40 bytes C#

In a case without discriminator and subclasses, iBATIS attempts to create an object with all values set to NULL, that is also incorrect.

Issue Links

• is related to: IBATIS-375 Provide a way for not creating items from nested ResultMaps when the items contain only null values