public virtual void BuildSelect(Expression selectExpression, TranslationContext context, Type expectedResultType = null)
{
// collect columns, split Expression in
// - things we will do in CLR
// - things we will do in SQL
expectedResultType = expectedResultType ?? selectExpression.Type;
LambdaExpression recordReaderExpr;
var dataRecordParameter = Expression.Parameter(typeof(IDataRecord), "dataRecord");
var sessionParameter = Expression.Parameter(typeof(EntitySession), "session");
// if we have a GroupByExpression, the result type is not the same:
// - we need to read what is going to be the Key expression
// - the final row generator builds a IGrouping<K,T> instead of T
var selectGroupExpression = selectExpression as GroupExpression;
if (selectGroupExpression != null)
{
var sqlOutExpr = CutOutSqlTierLambda(selectGroupExpression.GroupedExpression, dataRecordParameter, sessionParameter, null, context);
var selectKeyExpr = CutOutSqlTierLambda(selectGroupExpression.KeyExpression, dataRecordParameter, sessionParameter, null, context);
recordReaderExpr = sqlOutExpr;
if (selectGroupExpression.UseClrGrouping)
{
recordReaderExpr = BuildGroupByPairsReader(sqlOutExpr, selectKeyExpr, dataRecordParameter, sessionParameter, context);
var grouper = QueryResultsProcessor.CreateGroupBy(selectKeyExpr.Body.Type, sqlOutExpr.Body.Type);
context.CurrentSelect.ResultsProcessor = grouper;
context.CurrentSelect.Group.Remove(selectGroupExpression);
}
}
else
{
recordReaderExpr = CutOutSqlTierLambda(selectExpression, dataRecordParameter, sessionParameter, expectedResultType, context);
}
context.CurrentSelect.Reader = recordReaderExpr;
}
private TranslatedLinqCommand TranslateSelect(LinqCommand command)
{
LinqCommandPreprocessor.PreprocessCommand(_dbModel.EntityApp.Model, command);
var context = new TranslationContext(_dbModel, command);
var cmdInfo = command.Info;
// convert lambda params into an initial set of ExternalValueExpression objects;
foreach (var prm in cmdInfo.Lambda.Parameters)
{
var inpParam = new ExternalValueExpression(prm);
context.ExternalValues.Add(inpParam);
}
//Analyze/transform query expression
var exprChain = ExpressionChain.Build(cmdInfo.Lambda.Body);
var selectExpr = BuildSelectExpression(exprChain, context);
// Analyze external values (parameters?), create DbParameters
var commandParams = BuildParameters(command, context);
// If there's at least one parameter that must be converted to literal (ex: value list), we cannot cache the query
bool canCache = !context.ExternalValues.Any(v => v.SqlUse == ExternalValueSqlUse.Literal);
if (!canCache)
{
command.Info.Flags |= LinqCommandFlags.NoQueryCache;
}
//Build SQL, compile object materializer
var sqlBuilder = new SqlBuilder(_dbModel);
var sqlStatement = sqlBuilder.BuildSelect(selectExpr);
// Parameters are represented as {2}, {3}, etc.
// Braces in string literals are escaped and are represented as '{0}' and '{1}'
var sqlTemplate = sqlStatement.ToString();
var sql = FormatSql(sqlTemplate, commandParams);
var objMaterializer = CompileObjectMaterializer(context);
var outType = context.CurrentSelect.Reader.Body.Type;
var resultListCreator = ReflectionHelper.GetCompiledGenericListCreator(outType);
//check if we need to create implicit result set processor
if (selectExpr.ResultsProcessor == null)
{
var returnsResultSet = typeof(IQueryable).IsAssignableFrom(cmdInfo.Lambda.Body.Type);
if (!returnsResultSet)
{
selectExpr.ResultsProcessor = QueryResultsProcessor.CreateFirstSingleLast("First", outType);
}
}
var sqlQuery = new TranslatedLinqCommand(sqlTemplate, sql, commandParams, command.Info.Flags,
objMaterializer, selectExpr.ResultsProcessor, resultListCreator);
return(sqlQuery);
}