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