public static Remove ( ProjectionExpression projection ) : ProjectionExpression | ||
projection | ProjectionExpression | |
Результат | ProjectionExpression |
public static SelectExpression RemoveRedundantFrom(this SelectExpression select) { SelectExpression fromSelect = select.From as SelectExpression; if (fromSelect != null) { return(SubqueryRemover.Remove(select, fromSelect)); } return(select); }
protected override Expression VisitProjection(ProjectionExpression proj) { proj = (ProjectionExpression)base.VisitProjection(proj); if (proj.Select.From is SelectExpression) { List <SelectExpression> redundant = RedundantSubqueryGatherer.Gather(proj.Select); if (redundant != null) { proj = SubqueryRemover.Remove(proj, redundant); } } return(proj); }
protected override Expression VisitSelect(SelectExpression select) { select = (SelectExpression)base.VisitSelect(select); // first remove all purely redundant subqueries List <SelectExpression> redundant = RedundantSubqueryGatherer.Gather(select.From); if (redundant != null) { select = SubqueryRemover.Remove(select, redundant); } return(select); }
protected override Expression VisitSelect(SelectExpression select) { bool wasTopLevel = isTopLevel; isTopLevel = false; select = (SelectExpression)base.VisitSelect(select); // next attempt to merge subqueries that would have been removed by the above // logic except for the existence of a where clause while (CanMergeWithFrom(select, wasTopLevel)) { SelectExpression fromSelect = GetLeftMostSelect(select.From); // remove the redundant subquery select = SubqueryRemover.Remove(select, fromSelect); // merge where expressions Expression where = select.Where; if (fromSelect.Where != null) { if (where != null) { where = fromSelect.Where.And(where); } else { where = fromSelect.Where; } } var orderBy = select.OrderBy != null && select.OrderBy.Count > 0 ? select.OrderBy : fromSelect.OrderBy; var groupBy = select.GroupBy != null && select.GroupBy.Count > 0 ? select.GroupBy : fromSelect.GroupBy; Expression skip = select.Skip != null ? select.Skip : fromSelect.Skip; Expression take = select.Take != null ? select.Take : fromSelect.Take; bool isDistinct = select.IsDistinct | fromSelect.IsDistinct; if (where != select.Where || orderBy != select.OrderBy || groupBy != select.GroupBy || isDistinct != select.IsDistinct || skip != select.Skip || take != select.Take) { select = new SelectExpression(select.Alias, select.Columns, select.From, where, orderBy, groupBy, isDistinct, skip, take, select.IsReverse); } } return(select); }