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using System;
using System.Collections.Generic;
using System.Text;
using System.Data.Linq.Mapping;
using System.Data.Linq.Provider;
namespace System.Data.Linq.SqlClient {
/// <summary>
/// Hoist WHERE clauses as close to the root as possible.
/// </summary>
class SqlLiftWhereClauses {
internal static SqlNode Lift(SqlNode node, TypeSystemProvider typeProvider, MetaModel model) {
return new Lifter(typeProvider, model).Visit(node);
}
class Lifter : SqlVisitor {
private class Scope {
internal Scope Parent;
internal SqlExpression Where;
internal Scope(SqlExpression where, Scope parent) {
this.Where = where;
this.Parent = parent;
}
};
Scope current;
SqlFactory sql;
SqlAggregateChecker aggregateChecker;
SqlRowNumberChecker rowNumberChecker;
internal Lifter(TypeSystemProvider typeProvider, MetaModel model) {
this.sql = new SqlFactory(typeProvider, model);
this.aggregateChecker = new SqlAggregateChecker();
this.rowNumberChecker = new SqlRowNumberChecker();
}
internal override SqlSelect VisitSelect(SqlSelect select) {
Scope save = this.current;
this.current = new Scope(select.Where, this.current);
SqlSelect result = base.VisitSelect(select);
bool stopHoisting =
select.IsDistinct ||
select.GroupBy.Count > 0 ||
this.aggregateChecker.HasAggregates(select) ||
select.Top != null ||
this.rowNumberChecker.HasRowNumber(select);
// Shift as much of the current WHERE to the parent as possible.
if (this.current != null) {
if (this.current.Parent != null && !stopHoisting) {
this.current.Parent.Where = sql.AndAccumulate(this.current.Parent.Where, this.current.Where);
this.current.Where = null;
}
select.Where = this.current.Where;
}
this.current = save;
return result;
}
internal override SqlNode VisitUnion(SqlUnion su) {
Scope save = this.current;
this.current = null;
SqlNode result = base.VisitUnion(su);
this.current = save;
return result;
}
internal override SqlSource VisitJoin(SqlJoin join) {
// block where clauses from being lifted out of the cardinality-dependent
// side of an outer join.
Scope save = this.current;
try {
switch (join.JoinType) {
case SqlJoinType.Cross:
case SqlJoinType.CrossApply:
case SqlJoinType.Inner:
return base.VisitJoin(join);
case SqlJoinType.LeftOuter:
case SqlJoinType.OuterApply: {
join.Left = this.VisitSource(join.Left);
this.current = null;
join.Right = this.VisitSource(join.Right);
join.Condition = this.VisitExpression(join.Condition);
return join;
}
default:
this.current = null;
return base.VisitJoin(join);
}
}
finally {
this.current = save;
}
}
internal override SqlExpression VisitSubSelect(SqlSubSelect ss) {
// block where clauses from being lifted out of a sub-query
Scope save = this.current;
this.current = null;
SqlExpression result = base.VisitSubSelect(ss);
this.current = save;
return result;
}
internal override SqlExpression VisitClientQuery(SqlClientQuery cq) {
// block where clauses from being lifted out of a client-materialized sub-query
Scope save = this.current;
this.current = null;
SqlExpression result = base.VisitClientQuery(cq);
this.current = save;
return result;
}
}
}
}
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