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);
}
private IDbCommand CreateLinqDbCommand(DataConnection connection, LinqCommand linqCommand, TranslatedLinqCommand translatedCommand)
{
var cmd = connection.DbConnection.CreateCommand();
cmd.CommandType = CommandType.Text;
cmd.CommandText = translatedCommand.Sql;
foreach (var qParam in translatedCommand.Parameters)
{
var value = qParam.ReadValue(linqCommand.ParameterValues) ?? DBNull.Value;
var dbParam = cmd.CreateParameter(); //DbModel.Driver.AddParameter(cmd, //
dbParam.ParameterName = qParam.Name;
//Value and parameter may need some tweaking, depending on server type
DbModel.LinqSqlProvider.SetDbParameterValue(dbParam, qParam.Type, value);
cmd.Parameters.Add(dbParam);
}
return(cmd);
}
