64 lines
2.8 KiB
C#
64 lines
2.8 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Text;
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using System.Diagnostics.CodeAnalysis;
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namespace System.Data.Linq.SqlClient {
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internal class SqlUnionizer {
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internal static SqlNode Unionize(SqlNode node) {
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return new Visitor().Visit(node);
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}
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class Visitor : SqlVisitor {
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internal override SqlSelect VisitSelect(SqlSelect select) {
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base.VisitSelect(select);
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// enforce exact ordering of columns in union selects
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SqlUnion union = this.GetUnion(select.From);
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if (union != null) {
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SqlSelect sleft = union.Left as SqlSelect;
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SqlSelect sright = union.Right as SqlSelect;
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if (sleft != null & sright != null) {
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// preset ordinals to high values (so any unreachable column definition is ordered last)
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for (int i = 0, n = sleft.Row.Columns.Count; i < n; i++) {
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sleft.Row.Columns[i].Ordinal = select.Row.Columns.Count + i;
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}
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for (int i = 0, n = sright.Row.Columns.Count; i < n; i++) {
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sright.Row.Columns[i].Ordinal = select.Row.Columns.Count + i;
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}
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// next assign ordinals to all direct columns in subselects
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for (int i = 0, n = select.Row.Columns.Count; i < n; i++) {
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SqlExprSet es = select.Row.Columns[i].Expression as SqlExprSet;
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if (es != null) {
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for (int e = 0, en = es.Expressions.Count; e < en; e++) {
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SqlColumnRef cr = es.Expressions[e] as SqlColumnRef;
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if (cr != null && e >= select.Row.Columns.Count) {
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cr.Column.Ordinal = i;
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}
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}
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}
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}
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// next sort columns in left & right subselects
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Comparison<SqlColumn> comp = (x,y) => x.Ordinal - y.Ordinal;
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sleft.Row.Columns.Sort(comp);
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sright.Row.Columns.Sort(comp);
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}
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}
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return select;
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}
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[SuppressMessage("Microsoft.Performance", "CA1822:MarkMembersAsStatic", Justification="Unknown reason.")]
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private SqlUnion GetUnion(SqlSource source) {
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SqlAlias alias = source as SqlAlias;
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if (alias != null) {
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SqlUnion union = alias.Node as SqlUnion;
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if (union != null)
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return union;
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}
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return null;
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}
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}
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}
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}
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