Hello,

I am trying to write simple Exists function. The code looks like this:

public bool Exists<TEntity>(Guid primaryKey) where TEntity : EntityBase2, new() { IEntity2 entity = new TEntity();

IPredicate filterPredicate = new FieldCompareValuePredicate(entity.PrimaryKeyFields[0], null, ComparisonOperator.Equal, primaryKey);

var count = (int?)Database.GetScalar(entity.PrimaryKeyFields[0], null, AggregateFunction.CountRow, filterPredicate);
return count.GetValueOrDefault() > 0;

}

When I execute it, I get an error that Guid is not supported in MySQL. I just want to get simple query like: select count(*) from table where column = 'value';

It works with GetDbCount.. however I do not like subquery for such a simple thing Maybe you can suggest also other way to implement it?

Using LLBLGenPro 4.1-Final. Database: MySQL. Model first scenario.

regards Mantas

Please post the generated SQL query, and the exception stack trace.

Also why don't you just use adapter.FetchEntity()?

Its not able to generate query because of this exception

I am not using FetchEntity for performance reasons. However, probably it would be possible to use method overload with include/exclude field list.

Could you post the full stacktrace?

System.NotSupportedException : GUID variables are not supported in MySql databases.
   at SD.LLBLGen.Pro.DQE.MySql.MySqlSpecificCreator.DetermineDbTypeNameForValue(Object value, ref Object realValueToUse) in c:\Myprojects\VS.NET Projects\LLBLGen Pro v4.1\Frameworks\LLBLGen Pro\RuntimeLibraries\MySqlDQE\MySqlSpecificCreator.cs: line 134
   at SD.LLBLGen.Pro.ORMSupportClasses.DbSpecificCreatorBase.CreateParameter(ParameterDirection direction, Object valueToSet) in c:\Myprojects\VS.NET Projects\LLBLGen Pro v4.1\Frameworks\LLBLGen Pro\RuntimeLibraries\ORMSupportClasses\Persistence\DbSpecificCreatorBase.cs: line 162
   at SD.LLBLGen.Pro.ORMSupportClasses.FieldCompareValuePredicate.ToQueryText(Boolean inHavingClause) in c:\Myprojects\VS.NET Projects\LLBLGen Pro v4.1\Frameworks\LLBLGen Pro\RuntimeLibraries\ORMSupportClasses\QueryApiElements\FieldCompareValuePredicate.cs: line 292
   at SD.LLBLGen.Pro.ORMSupportClasses.PredicateExpression.ToQueryText(Boolean inHavingClause) in c:\Myprojects\VS.NET Projects\LLBLGen Pro v4.1\Frameworks\LLBLGen Pro\RuntimeLibraries\ORMSupportClasses\QueryApiElements\PredicateExpression.cs: line 226
   at SD.LLBLGen.Pro.ORMSupportClasses.DynamicQueryEngineBase.AppendWhereClause(IPredicate filter, QueryFragments destination, IQuery query) in c:\Myprojects\VS.NET Projects\LLBLGen Pro v4.1\Frameworks\LLBLGen Pro\RuntimeLibraries\ORMSupportClasses\Persistence\DynamicQueryEngineBase.cs: line 1581
   at SD.LLBLGen.Pro.ORMSupportClasses.DynamicQueryEngineBase.CreateSelectDQ(IEntityFieldCore[] selectList, IFieldPersistenceInfo[] fieldsPersistenceInfo, IRetrievalQuery query, IPredicate selectFilter, Int64 maxNumberOfItemsToReturn, ISortExpression sortClauses, IRelationCollection relationsToWalk, Boolean allowDuplicates, IGroupByCollection groupByClause, Boolean relationsSpecified, Boolean sortClausesSpecified) in c:\Myprojects\VS.NET Projects\LLBLGen Pro v4.1\Frameworks\LLBLGen Pro\RuntimeLibraries\ORMSupportClasses\Persistence\DynamicQueryEngineBase.cs: line 1267
   at SD.LLBLGen.Pro.ORMSupportClasses.DynamicQueryEngineBase.CreateSelectDQ(IEntityFieldCore[] selectList, IFieldPersistenceInfo[] fieldsPersistenceInfo, DbConnection connectionToUse, IPredicate selectFilter, Int64 maxNumberOfItemsToReturn, ISortExpression sortClauses, IRelationCollection relationsToWalk, Boolean allowDuplicates, IGroupByCollection groupByClause) in c:\Myprojects\VS.NET Projects\LLBLGen Pro v4.1\Frameworks\LLBLGen Pro\RuntimeLibraries\ORMSupportClasses\Persistence\DynamicQueryEngineBase.cs: line 1128
   at SD.LLBLGen.Pro.DQE.MySql.DynamicQueryEngine.CreatePagingSelectDQ(IEntityFieldCore[] selectList, IFieldPersistenceInfo[] fieldsPersistenceInfo, DbConnection connectionToUse, IPredicate selectFilter, Int32 rowsToSkip, Int32 rowsToTake, ISortExpression sortClauses, IRelationCollection relationsToWalk, Boolean allowDuplicates, IGroupByCollection groupByClause) in c:\Myprojects\VS.NET Projects\LLBLGen Pro v4.1\Frameworks\LLBLGen Pro\RuntimeLibraries\MySqlDQE\DynamicQueryEngine.cs: line 284
   at SD.LLBLGen.Pro.ORMSupportClasses.DataAccessAdapterBase.CreateSelectDQ(QueryParameters parameters) in c:\Myprojects\VS.NET Projects\LLBLGen Pro v4.1\Frameworks\LLBLGen Pro\RuntimeLibraries\ORMSupportClasses\AdapterSpecific\DataAccessAdapterBase.cs: line 4155
   at Visma.School.DataAccess.Repositories.Context.MySqlDataAccessAdapter.CreateSelectDQ(QueryParameters parameters) in MySqlDataAccessAdapter.cs: line 34
   at SD.LLBLGen.Pro.ORMSupportClasses.DataAccessAdapterBase.GetScalar(IEntityFields2 fields, IPredicate filter, IGroupByCollection groupByClause, IRelationCollection relations) in c:\Myprojects\VS.NET Projects\LLBLGen Pro v4.1\Frameworks\LLBLGen Pro\RuntimeLibraries\ORMSupportClasses\AdapterSpecific\DataAccessAdapterBase.cs: line 373
   at SD.LLBLGen.Pro.ORMSupportClasses.DataAccessAdapterBase.GetScalar(IEntityField2 field, IExpression expressionToExecute, AggregateFunction aggregateToApply, IPredicate filter, IGroupByCollection groupByClause, IRelationCollection relations) in c:\Myprojects\VS.NET Projects\LLBLGen Pro v4.1\Frameworks\LLBLGen Pro\RuntimeLibraries\ORMSupportClasses\AdapterSpecific\DataAccessAdapterBase.cs: line 296
   at SD.LLBLGen.Pro.ORMSupportClasses.DataAccessAdapterBase.GetScalar(IEntityField2 field, IExpression expressionToExecute, AggregateFunction aggregateToApply, IPredicate filter) in c:\Myprojects\VS.NET Projects\LLBLGen Pro v4.1\Frameworks\LLBLGen Pro\RuntimeLibraries\ORMSupportClasses\AdapterSpecific\DataAccessAdapterBase.cs: line 244
   at Visma.School.DataAccess.Repositories.EntityRepository`1.Exists(Guid primaryKey) in EntityRepository.cs: line 69
   at Visma.School.DataAccess.Repositories.EntityRepository`1.Exists(Guid primaryKey) in EntityRepository.cs: line 50

At Line: 69: var count = (int?)Database.GetScalar(entity.PrimaryKeyFields[0], null, AggregateFunction.CountRow, filterPredicate); from function in first post.

The problem is caused by the Guid value itself. The query engine has no idea how to convert that to a value which is usable in the DB. So if you map guid fields to a byte[] field you should pre-convert the guid to a byte array and pass that as value in the predicate. The engine doesn't use the type converter set on the field to convert the guid value. I admit, this is possible, but only in a subset of cases: expressions compared to a field for example are not possible to re-use the typeconverter. Is it a problem to convert the guid before assigning it to the predicate?

It seems that passing byte array value solved the problem. Thank you very much.