Пример #1
0
        protected override Expression VisitSelect(SelectExpression select)
        {
            bool saveIsOuterMostSelect = this.isOuterMostSelect;

            try
            {
                this.isOuterMostSelect = false;
                select = (SelectExpression)base.VisitSelect(select);

                bool hasOrderBy          = select.OrderBy != null && select.OrderBy.Count > 0;
                bool hasGroupBy          = select.GroupBy != null && select.GroupBy.Count > 0;
                bool canHaveOrderBy      = saveIsOuterMostSelect || select.Take != null || select.Skip != null;
                bool canReceiveOrderings = canHaveOrderBy && !hasGroupBy && !select.IsDistinct;

                if (hasOrderBy)
                {
                    this.PrependOrderings(select.OrderBy);
                }

                IEnumerable <OrderExpression> orderings = null;
                if (canReceiveOrderings)
                {
                    orderings = this.gatheredOrderings;
                }
                else if (canHaveOrderBy)
                {
                    orderings = select.OrderBy;
                }
                bool canPassOnOrderings = !saveIsOuterMostSelect && !hasGroupBy && !select.IsDistinct;
                ReadOnlyCollection <ColumnDeclaration> columns = select.Columns;
                if (this.gatheredOrderings != null)
                {
                    if (canPassOnOrderings)
                    {
                        var producedAliases = DeclaredAliasGatherer.Gather(select.From);
                        // reproject order expressions using this select's alias so the outer select will have properly formed expressions
                        BindResult project = this.RebindOrderings(this.gatheredOrderings, select.Alias, producedAliases, select.Columns);
                        this.gatheredOrderings = null;
                        this.PrependOrderings(project.Orderings);
                        columns = project.Columns;
                    }
                    else
                    {
                        this.gatheredOrderings = null;
                    }
                }
                if (orderings != select.OrderBy || columns != select.Columns)
                {
                    select = new SelectExpression(select.Alias, columns, select.From, select.Where, orderings, select.GroupBy, select.IsDistinct, select.Skip, select.Take);
                }
                return(select);
            }
            finally
            {
                this.isOuterMostSelect = saveIsOuterMostSelect;
            }
        }
Пример #2
0
        protected override Expression VisitJoin(JoinExpression join)
        {
            join = (JoinExpression)base.VisitJoin(join);

            if (join.Join == JoinType.CrossApply || join.Join == JoinType.OuterApply)
            {
                if (join.Right is TableExpression)
                {
                    return(new JoinExpression(JoinType.CrossJoin, join.Left, join.Right, null));
                }
                else
                {
                    SelectExpression select = join.Right as SelectExpression;
                    // Only consider rewriting cross apply if
                    //   1) right side is a select
                    //   2) other than in the where clause in the right-side select, no left-side declared aliases are referenced
                    //   3) and has no behavior that would change semantics if the where clause is removed (like groups, aggregates, take, skip, etc).
                    // Note: it is best to attempt this after redundant subqueries have been removed.
                    if (select != null &&
                        select.Take == null &&
                        select.Skip == null &&
                        !AggregateChecker.HasAggregates(select) &&
                        (select.GroupBy == null || select.GroupBy.Count == 0))
                    {
                        SelectExpression     selectWithoutWhere = select.SetWhere(null);
                        HashSet <TableAlias> referencedAliases  = ReferencedAliasGatherer.Gather(selectWithoutWhere);
                        HashSet <TableAlias> declaredAliases    = DeclaredAliasGatherer.Gather(join.Left);
                        referencedAliases.IntersectWith(declaredAliases);
                        if (referencedAliases.Count == 0)
                        {
                            Expression where = select.Where;
                            select           = selectWithoutWhere;
                            var pc = ColumnProjector.ProjectColumns(this.CanBeColumn, where, select.Columns, select.Alias, DeclaredAliasGatherer.Gather(select.From));
                            select = select.SetColumns(pc.Columns);
                            where  = pc.Projector;
                            JoinType jt = (where == null) ? JoinType.CrossJoin : (join.Join == JoinType.CrossApply ? JoinType.InnerJoin : JoinType.LeftOuter);
                            return(new JoinExpression(jt, join.Left, select, where));
                        }
                    }
                }
            }

            return(join);
        }