protected virtual EntityRecordReader CreateEntityReader(TableExpression tableExpression,
TranslationContext context)
{
// Note: we have to create EntityRecordReader each time, because column indexes in output can change from query to query
var reader = new EntityRecordReader(tableExpression.TableInfo);
var allColExprs = RegisterAllColumns(tableExpression, context);
foreach (var col in allColExprs)
{
var colIndex = RegisterOutputValue(col, context);
reader.AddColumn(col.ColumnInfo, colIndex);
}
return(reader);
}
public virtual void BuildSelectResultReaderAndCutOutSql(Expression forExpr, TranslationContext context, Type expectedResultType)
{
// collect columns, split Expression in
// - things we will do in CLR
// - things we will do in SQL
LambdaExpression readerLambda; //do not try to get rid of this var; context.CurrentSelect can change by the end of the method
EntityRecordReader entReader = null;
var dataRecordParameter = Expression.Parameter(typeof(IDataRecord), "dataRecord");
var sessionParameter = Expression.Parameter(typeof(Entities.Runtime.EntitySession), "session");
// This is special optimization case for reading entities, to avoid Lambda.Compile, we use
// instance of EntityRecordReader directly. DO NOT try to optimize or improve it!!! (talking to you, Roman)
bool isSelectOp = context.Command.Operation == LinqOperation.Select;
if (isSelectOp && forExpr is TableExpression tableExpr)
{
entReader = CreateEntityReader(tableExpr, context);
readerLambda = null;
}
// 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
else if (forExpr is GroupExpression groupExpression)
{
var sqlOutExpr = CutOutSqlTierLambda(groupExpression.GroupedExpression, dataRecordParameter, sessionParameter, null, context);
var selectKeyExpr = CutOutSqlTierLambda(groupExpression.KeyExpression, dataRecordParameter, sessionParameter, null, context);
readerLambda = sqlOutExpr;
if (groupExpression.UseClrGrouping)
{
readerLambda = BuildGroupByPairsReader(sqlOutExpr, selectKeyExpr, dataRecordParameter, sessionParameter, context);
var grouper = RowListProcessor.CreateGroupBy(selectKeyExpr.Body.Type, sqlOutExpr.Body.Type);
context.CurrentSelect.RowListProcessor = grouper;
context.CurrentSelect.Group.Remove(groupExpression);
}
}
else
{
readerLambda = CutOutSqlTierLambda(forExpr, dataRecordParameter, sessionParameter, expectedResultType, context);
}
// wait until the end to assign these, CurrentSelect might have changed
context.CurrentSelect.EntityReader = entReader;
context.CurrentSelect.RowReaderLambda = readerLambda;
}
