1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
|
using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Data.Linq;
namespace System.Data.Linq.SqlClient {
// converts correlated scalar subqueries into outer-applies
// must be run after flattener.
internal class SqlRewriteScalarSubqueries {
Visitor visitor;
internal SqlRewriteScalarSubqueries(SqlFactory sqlFactory) {
this.visitor = new Visitor(sqlFactory);
}
internal SqlNode Rewrite(SqlNode node) {
return this.visitor.Visit(node);
}
class Visitor : SqlVisitor {
SqlFactory sql;
SqlSelect currentSelect;
SqlAggregateChecker aggregateChecker;
internal Visitor(SqlFactory sqlFactory) {
this.sql = sqlFactory;
this.aggregateChecker = new SqlAggregateChecker();
}
internal override SqlExpression VisitScalarSubSelect(SqlSubSelect ss) {
SqlSelect innerSelect = this.VisitSelect(ss.Select);
if (!this.aggregateChecker.HasAggregates(innerSelect)) {
innerSelect.Top = this.sql.ValueFromObject(1, ss.SourceExpression);
}
innerSelect.OrderingType = SqlOrderingType.Blocked;
SqlAlias alias = new SqlAlias(innerSelect);
this.currentSelect.From = new SqlJoin(SqlJoinType.OuterApply, this.currentSelect.From, alias, null, ss.SourceExpression);
return new SqlColumnRef(innerSelect.Row.Columns[0]);
}
internal override SqlSelect VisitSelect(SqlSelect select) {
SqlSelect save = this.currentSelect;
try {
this.currentSelect = select;
return base.VisitSelect(select);
}
finally {
this.currentSelect = save;
}
}
}
}
}
|
