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using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
namespace System.Data.Linq.SqlClient {
using System.Data.Linq;
/// <summary>
/// Turn CROSS APPLY into CROSS JOIN when the right side
/// of the apply doesn't reference anything on the left side.
///
/// Any query which has a CROSS APPLY which cannot be converted to
/// a CROSS JOIN is annotated so that we can give a meaningful
/// error message later for SQL2K.
/// </summary>
internal class SqlCrossApplyToCrossJoin {
internal static SqlNode Reduce(SqlNode node, SqlNodeAnnotations annotations) {
Reducer r = new Reducer();
r.Annotations = annotations;
return r.Visit(node);
}
class Reducer : SqlVisitor {
internal SqlNodeAnnotations Annotations;
internal override SqlSource VisitJoin(SqlJoin join) {
if (join.JoinType == SqlJoinType.CrossApply) {
// Look down the left side to see what table aliases are produced.
HashSet<SqlAlias> p = SqlGatherProducedAliases.Gather(join.Left);
// Look down the right side to see what table aliases are consumed.
HashSet<SqlAlias> c = SqlGatherConsumedAliases.Gather(join.Right);
// Look at each consumed alias and see if they are mentioned in produced.
if (p.Overlaps(c)) {
Annotations.Add(join, new SqlServerCompatibilityAnnotation(Strings.SourceExpressionAnnotation(join.SourceExpression), SqlProvider.ProviderMode.Sql2000));
// Can't reduce because this consumed alias is produced on the left.
return base.VisitJoin(join);
}
// Can turn this into a CROSS JOIN
join.JoinType = SqlJoinType.Cross;
return VisitJoin(join);
}
return base.VisitJoin(join);
}
}
}
}
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