69 lines
2.1 KiB
C#
69 lines
2.1 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Text;
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namespace System.Data.Linq.SqlClient
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{
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/// <summary>
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/// Find referenced Aliases within a node.
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/// </summary>
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internal static class SqlAliasesReferenced
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{
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/// <summary>
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/// Private visitor which walks the tree and looks for referenced aliases.
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/// </summary>
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private class Visitor : SqlVisitor {
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internal IEnumerable<SqlAlias> aliases;
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internal bool referencesAnyMatchingAliases = false;
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internal override SqlNode Visit(SqlNode node) {
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// Short-circuit when the answer is alreading known
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if (this.referencesAnyMatchingAliases) {
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return node;
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}
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return base.Visit(node);
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}
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internal SqlAlias VisitAliasConsumed(SqlAlias a) {
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if (a == null)
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return a;
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bool match = false;
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foreach (SqlAlias alias in aliases)
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if (alias == a) {
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match = true;
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break;
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}
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if (match) {
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this.referencesAnyMatchingAliases = true;
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}
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return a;
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}
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internal override SqlExpression VisitColumn(SqlColumn col) {
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VisitAliasConsumed(col.Alias);
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VisitExpression(col.Expression);
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return col;
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}
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internal override SqlExpression VisitColumnRef(SqlColumnRef cref) {
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VisitAliasConsumed(cref.Column.Alias);
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VisitExpression(cref.Column.Expression);
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return cref;
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}
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}
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/// <summary>
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/// Returns true iff the given node references any aliases the list of 'aliases'.
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/// </summary>
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internal static bool ReferencesAny(SqlNode node, IEnumerable<SqlAlias> aliases) {
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Visitor visitor = new Visitor();
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visitor.aliases = aliases;
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visitor.Visit(node);
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return visitor.referencesAnyMatchingAliases;
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}
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}
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}
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