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Imported Upstream version 4.6.0.125

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2016-08-03 10:59:49 +00:00
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mcs/class/referencesource/System.Data.Entity/System/Data/SqlClient/SqlGen/Sql8ExpressionRewriter.cs Normal file
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//---------------------------------------------------------------------
// <copyright file="Sql8ExpressionRewriter.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//
// @owner [....]
// @backupOwner [....]
//---------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.Data.Common;
using System.Data.Common.CommandTrees;
using System.Data.Common.CommandTrees.Internal;
using System.Data.Metadata.Edm;
using System.Data.Common.CommandTrees.ExpressionBuilder;
namespace System.Data.SqlClient.SqlGen
{
/// <summary>
/// Rewrites an expression tree to make it suitable for translation to SQL appropriate for SQL Server 2000
/// In particular, it replaces expressions that are not directly supported on SQL Server 2000
/// with alternative translations. The following expressions are translated:
/// <list type="bullet">
/// <item><see cref="DbExceptExpression"/></item>
/// <item><see cref="DbIntersectExpression"/></item>
/// <item><see cref="DbSkipExpression"/></item>
/// </list>
///
/// The other expressions are copied unmodified.
/// The new expression belongs to a new query command tree.
/// </summary>
internal class Sql8ExpressionRewriter : DbExpressionRebinder
{
#region Entry Point
/// <summary>
/// The only entry point.
/// Rewrites the given tree by replacing expressions that are not directly supported on SQL Server 2000
/// with alterntive translations.
/// </summary>
/// <param name="originalTree">The tree to rewrite</param>
/// <returns>The new tree</returns>
internal static DbQueryCommandTree Rewrite(DbQueryCommandTree originalTree)
{
Debug.Assert(originalTree != null, "OriginalTree is null");
Sql8ExpressionRewriter rewriter = new Sql8ExpressionRewriter(originalTree.MetadataWorkspace);
DbExpression newQuery = rewriter.VisitExpression(originalTree.Query);
return DbQueryCommandTree.FromValidExpression(originalTree.MetadataWorkspace, originalTree.DataSpace, newQuery);
}
#endregion
#region Constructor
/// <summary>
/// Private Constructor.
/// </summary>
/// <param name="metadata"></param>
private Sql8ExpressionRewriter(MetadataWorkspace metadata)
:base(metadata)
{
}
#endregion
#region DbExpressionVisitor<DbExpression> Members
/// <summary>
/// <see cref="TransformIntersectOrExcept(DbExpression left, DbExpression right, DbExpressionKind expressionKind, IList<DbPropertyExpression> sortExpressionsOverLeft, string sortExpressionsBindingVariableName)"/>
/// </summary>
/// <param name="e"></param>
/// <returns></returns>
public override DbExpression Visit(DbExceptExpression e)
{
return TransformIntersectOrExcept(VisitExpression(e.Left), VisitExpression(e.Right), DbExpressionKind.Except);
}
/// <summary>
/// <see cref="TransformIntersectOrExcept(DbExpression left, DbExpression right, DbExpressionKind expressionKind, IList<DbPropertyExpression> sortExpressionsOverLeft, string sortExpressionsBindingVariableName)"/>
/// </summary>
/// <param name="e"></param>
/// <returns></returns>
public override DbExpression Visit(DbIntersectExpression e)
{
return TransformIntersectOrExcept(VisitExpression(e.Left), VisitExpression(e.Right), DbExpressionKind.Intersect);
}
/// <summary>
/// Logicaly, <see cref="DbSkipExpression"/> translates to:
/// SELECT Y.x1, Y.x2, ..., Y.xn
/// FROM (
/// SELECT X.x1, X.x2, ..., X.xn,
/// FROM input AS X
/// EXCEPT
/// SELECT TOP(count) Z.x1, Z.x2, ..., Z.xn
/// FROM input AS Z
/// ORDER BY sk1, sk2, ...
/// ) AS Y
/// ORDER BY sk1, sk2, ...
///
/// Here, input refers to the input of the <see cref="DbSkipExpression"/>, and count to the count property of the <see cref="DbSkipExpression"/>.
/// The implementation of EXCEPT is non-duplicate eliminating, and does equality comparison only over the
/// equality comparable columns of the input.
///
/// This corresponds to the following expression tree:
///
/// SORT
/// |
/// NON-DISTINCT EXCEPT (specially translated, <see cref="TransformIntersectOrExcept(DbExpression left, DbExpression right, DbExpressionKind expressionKind, IList<DbPropertyExpression> sortExpressionsOverLeft, string sortExpressionsBindingVariableName)"/>
/// |
/// | - Left: clone of input
/// | - Right:
/// |
/// Limit
/// |
/// | - Limit: Count
/// | - Input
/// |
/// Sort
/// |
/// input
///
/// </summary>
/// <param name="e"></param>
/// <returns></returns>
public override DbExpression Visit(DbSkipExpression e)
{
//Build the right input of the except
DbExpression rightInput = VisitExpressionBinding(e.Input).Sort(VisitSortOrder(e.SortOrder)).Limit(VisitExpression(e.Count));
//Build the left input for the except
DbExpression leftInput = VisitExpression(e.Input.Expression); //Another copy of the input
IList<DbSortClause> sortOrder = VisitSortOrder(e.SortOrder); //Another copy of the sort order
// Create a list of the sort expressions to be used for translating except
IList<DbPropertyExpression> sortExpressions = new List<DbPropertyExpression>(e.SortOrder.Count);
foreach (DbSortClause sortClause in sortOrder)
{
//We only care about property expressions, not about constants
if (sortClause.Expression.ExpressionKind == DbExpressionKind.Property)
{
sortExpressions.Add((DbPropertyExpression)sortClause.Expression);
}
}
DbExpression exceptExpression = TransformIntersectOrExcept(leftInput, rightInput, DbExpressionKind.Skip, sortExpressions, e.Input.VariableName);
DbExpression result = exceptExpression.BindAs(e.Input.VariableName).Sort(sortOrder);
return result;
}
#endregion
#region DbExpressionVisitor<DbExpression> Member Helpers
/// <summary>
/// This method is invoked when tranforming <see cref="DbIntersectExpression"/> and <see cref="DbExceptExpression"/> by doing comparison over all input columns.
/// <see cref="TransformIntersectOrExcept(DbExpression left, DbExpression right, DbExpressionKind expressionKind, IList<DbPropertyExpression> sortExpressionsOverLeft, string sortExpressionsBindingVariableName)"/>
/// </summary>
/// <param name="left"></param>
/// <param name="right"></param>
/// <param name="expressionKind"></param>
/// <returns></returns>
private DbExpression TransformIntersectOrExcept(DbExpression left, DbExpression right, DbExpressionKind expressionKind)
{
return TransformIntersectOrExcept( left, right, expressionKind, null, null);
}
/// <summary>
/// This method is used for translating <see cref="DbIntersectExpression"/> and <see cref="DbExceptExpression"/>,
/// and for translating the "Except" part of <see cref="DbSkipExpression"/>.
/// into the follwoing expression:
///
/// A INTERSECT B, A EXCEPT B
///
/// (DISTINCT)
/// |
/// FILTER
/// |
/// | - Input: A
/// | - Predicate:(NOT)
/// |
/// ANY
/// |
/// | - Input: B
/// | - Predicate: (B.b1 = A.a1 or (B.b1 is null and A.a1 is null))
/// AND (B.b2 = A.a2 or (B.b2 is null and A.a2 is null))
/// AND ...
/// AND (B.bn = A.an or (B.bn is null and A.an is null)))
///
/// Here, A corresponds to right and B to left.
/// (NOT) is present when transforming Except
/// for the purpose of translating <see cref="DbExceptExpression"/> or <see cref="DbSkipExpression"/>.
/// (DISTINCT) is present when transforming for the purpose of translating
/// <see cref="DbExceptExpression"/> or <see cref="DbIntersectExpression"/>.
///
/// For <see cref="DbSkipExpression"/>, the input to ANY is caped with project which projects out only
/// the columns represented in the sortExpressionsOverLeft list and only these are used in the predicate.
/// This is because we want to support skip over input with non-equal comarable columns and we have no way to recognize these.
/// </summary>
/// <param name="left"></param>
/// <param name="right"></param>
/// <param name="expressionKind"></param>
/// <param name="sortExpressionsOverLeft">note that this list gets destroyed by this method</param>
/// <param name="sortExpressionsBindingVariableName"></param>
/// <returns></returns>
private DbExpression TransformIntersectOrExcept(DbExpression left, DbExpression right, DbExpressionKind expressionKind, IList<DbPropertyExpression> sortExpressionsOverLeft, string sortExpressionsBindingVariableName)
{
bool negate = (expressionKind == DbExpressionKind.Except) || (expressionKind == DbExpressionKind.Skip);
bool distinct = (expressionKind == DbExpressionKind.Except) || (expressionKind == DbExpressionKind.Intersect);
DbExpressionBinding leftInputBinding = left.Bind();
DbExpressionBinding rightInputBinding = right.Bind();
IList<DbPropertyExpression> leftFlattenedProperties = new List<DbPropertyExpression>();
IList<DbPropertyExpression> rightFlattenedProperties = new List<DbPropertyExpression>();
FlattenProperties(leftInputBinding.Variable, leftFlattenedProperties);
FlattenProperties(rightInputBinding.Variable, rightFlattenedProperties);
//For Skip, we need to ignore any columns that are not in the original sort list. We can recognize these by comparing the left flattened properties and
// the properties in the list sortExpressionsOverLeft
// If any such columns exist, we need to add an additional project, to keep the rest of the columns from being projected, as if any among these
// are non equal comparable, SQL Server 2000 throws.
if (expressionKind == DbExpressionKind.Skip)
{
if (RemoveNonSortProperties(leftFlattenedProperties, rightFlattenedProperties, sortExpressionsOverLeft, leftInputBinding.VariableName, sortExpressionsBindingVariableName))
{
rightInputBinding = CapWithProject(rightInputBinding, rightFlattenedProperties);
}
}
Debug.Assert(leftFlattenedProperties.Count == rightFlattenedProperties.Count, "The left and the right input to INTERSECT or EXCEPT have a different number of properties");
Debug.Assert(leftFlattenedProperties.Count != 0, "The inputs to INTERSECT or EXCEPT have no properties");
//Build the predicate for the quantifier:
// (B.b1 = A.a1 or (B.b1 is null and A.a1 is null))
// AND (B.b2 = A.a2 or (B.b2 is null and A.a2 is null))
// AND ...
// AND (B.bn = A.an or (B.bn is null and A.an is null)))
DbExpression existsPredicate = null;
for (int i = 0; i < leftFlattenedProperties.Count; i++)
{
//A.ai == B.bi
DbExpression equalsExpression = leftFlattenedProperties[i].Equal(rightFlattenedProperties[i]);
//A.ai is null AND B.bi is null
DbExpression leftIsNullExpression = leftFlattenedProperties[i].IsNull();
DbExpression rightIsNullExpression = rightFlattenedProperties[i].IsNull();
DbExpression bothNullExpression = leftIsNullExpression.And(rightIsNullExpression);
DbExpression orExpression = equalsExpression.Or(bothNullExpression);
if (i == 0)
{
existsPredicate = orExpression;
}
else
{
existsPredicate = existsPredicate.And(orExpression);
}
}
//Build the quantifier
DbExpression quantifierExpression = rightInputBinding.Any(existsPredicate);
DbExpression filterPredicate;
//Negate if needed
if (negate)
{
filterPredicate = quantifierExpression.Not();
}
else
{
filterPredicate = quantifierExpression;
}
//Build the filter
DbExpression result = leftInputBinding.Filter(filterPredicate);
//Apply distinct in needed
if (distinct)
{
result = result.Distinct();
}
return result;
}
/// <summary>
/// Adds the flattened properties on the input to the flattenedProperties list.
/// </summary>
/// <param name="input"></param>
/// <param name="flattenedProperties"></param>
private void FlattenProperties(DbExpression input, IList<DbPropertyExpression> flattenedProperties)
{
IList<EdmProperty> properties = TypeHelpers.GetProperties(input.ResultType);
Debug.Assert(properties.Count != 0, "No nested properties when FlattenProperties called?");
for (int i = 0; i < properties.Count; i++)
{
DbExpression propertyInput = input;
DbPropertyExpression propertyExpression = propertyInput.Property(properties[i]);
if (TypeSemantics.IsPrimitiveType(properties[i].TypeUsage))
{
flattenedProperties.Add(propertyExpression);
}
else
{
Debug.Assert(TypeSemantics.IsEntityType(properties[i].TypeUsage) || TypeSemantics.IsRowType(properties[i].TypeUsage),
"The input to FlattenProperties is not of EntityType or RowType?");
FlattenProperties(propertyExpression, flattenedProperties);
}
}
}
/// <summary>
/// Helper method for <see cref="TransformIntersectOrExcept(DbExpression left, DbExpression right, DbExpressionKind expressionKind, IList<DbPropertyExpression> sortExpressionsOverLeft, string sortExpressionsBindingVariableName)"/>
/// Removes all pairs of property expressions from list1 and list2, for which the property expression in list1
/// does not have a 'matching' property expression in list2.
/// The lists list1 and list2 are known to not create duplicate, and the purpose of the sortList is just for this method.
/// Thus, to optimize the match process, we remove the seen property expressions from the sort list in <see cref="HasMatchInList"/>
/// when iterating both list simultaneously.
/// </summary>
/// <param name="list1"></param>
/// <param name="list2"></param>
/// <param name="sortList"></param>
/// <param name="list1BindingVariableName"></param>
/// <param name="sortExpressionsBindingVariableName"></param>
/// <returns></returns>
private static bool RemoveNonSortProperties(IList<DbPropertyExpression> list1, IList<DbPropertyExpression> list2, IList<DbPropertyExpression> sortList, string list1BindingVariableName, string sortExpressionsBindingVariableName)
{
bool result = false;
for (int i = list1.Count - 1; i >= 0; i--)
{
if (!HasMatchInList(list1[i], sortList, list1BindingVariableName, sortExpressionsBindingVariableName))
{
list1.RemoveAt(i);
list2.RemoveAt(i);
result = true;
}
}
return result;
}
/// <summary>
/// Helper method for <see cref="RemoveNonSortProperties"/>
/// Checks whether expr has a 'match' in the given list of property expressions.
/// If it does, the matching expression is removed form the list, to speed up future matching.
/// </summary>
/// <param name="expr"></param>
/// <param name="sortList"></param>
/// <param name="exprBindingVariableName"></param>
/// <param name="sortExpressionsBindingVariableName"></param>
/// <returns></returns>
private static bool HasMatchInList(DbPropertyExpression expr, IList<DbPropertyExpression> list, string exprBindingVariableName, string listExpressionsBindingVariableName)
{
for (int i=0; i<list.Count; i++)
{
if (AreMatching(expr, list[i], exprBindingVariableName, listExpressionsBindingVariableName))
{
// This method is used for matching element of two list without duplicates,
// thus if match is found, remove it from the list, to speed up future matching.
list.RemoveAt(i);
return true;
}
}
return false;
}
/// <summary>
/// Determines whether two expressions match.
/// They match if they are of the shape
/// expr1 -> DbPropertyExpression(... (DbPropertyExpression(DbVariableReferenceExpression(expr1BindingVariableName), nameX), ..., name1)
/// expr1 -> DbPropertyExpression(... (DbPropertyExpression(DbVariableReferenceExpression(expr2BindingVariableName), nameX), ..., name1),
///
/// i.e. if they only differ in the name of the binding.
/// </summary>
/// <param name="expr1"></param>
/// <param name="expr2"></param>
/// <param name="expr1BindingVariableName"></param>
/// <param name="expr2BindingVariableName"></param>
/// <returns></returns>
private static bool AreMatching(DbPropertyExpression expr1, DbPropertyExpression expr2, string expr1BindingVariableName, string expr2BindingVariableName)
{
if (expr1.Property.Name != expr2.Property.Name)
{
return false;
}
if (expr1.Instance.ExpressionKind != expr2.Instance.ExpressionKind)
{
return false;
}
if (expr1.Instance.ExpressionKind == DbExpressionKind.Property)
{
return AreMatching((DbPropertyExpression)expr1.Instance, (DbPropertyExpression)expr2.Instance, expr1BindingVariableName, expr2BindingVariableName);
}
DbVariableReferenceExpression instance1 = (DbVariableReferenceExpression)expr1.Instance;
DbVariableReferenceExpression instance2 = (DbVariableReferenceExpression)expr2.Instance;
return (String.Equals(instance1.VariableName, expr1BindingVariableName, StringComparison.Ordinal)
&& String.Equals(instance2.VariableName, expr2BindingVariableName, StringComparison.Ordinal));
}
/// <summary>
/// Helper method for <see cref="TransformIntersectOrExcept(DbExpression left, DbExpression right, DbExpressionKind expressionKind, IList<DbPropertyExpression> sortExpressionsOverLeft, string sortExpressionsBindingVariableName)"/>
/// Creates a <see cref="DbProjectExpression"/> over the given inputBinding that projects out the given flattenedProperties.
/// and updates the flattenedProperties to be over the newly created project.
/// </summary>
/// <param name="inputBinding"></param>
/// <param name="flattenedProperties"></param>
/// <returns>An <see cref="DbExpressionBinding"/> over the newly created <see cref="DbProjectExpression"/></returns>
private DbExpressionBinding CapWithProject(DbExpressionBinding inputBinding, IList<DbPropertyExpression> flattenedProperties)
{
List<KeyValuePair<string, DbExpression>> projectColumns = new List<KeyValuePair<string, DbExpression>>(flattenedProperties.Count);
//List of all the columnNames used in the projection.
Dictionary<string, int> columnNames = new Dictionary<string, int>(flattenedProperties.Count);
foreach (DbPropertyExpression pe in flattenedProperties)
{
//There may be conflicting property names, thus we may need to rename.
string name = pe.Property.Name;
int i;
if (columnNames.TryGetValue(name, out i))
{
string newName;
do
{
++i;
newName = name + i.ToString(System.Globalization.CultureInfo.InvariantCulture);
} while (columnNames.ContainsKey(newName));
columnNames[name] = i;
name = newName;
}
// Add this column name to list of known names so that there are no subsequent
// collisions
columnNames[name] = 0;
projectColumns.Add(new KeyValuePair<string, DbExpression>(name, pe));
}
//Build the project
DbExpression rowExpr = DbExpressionBuilder.NewRow(projectColumns);
DbProjectExpression projectExpression = inputBinding.Project(rowExpr);
//Create the new inputBinding
DbExpressionBinding resultBinding = projectExpression.Bind();
//Create the list of flattenedProperties over the new project
flattenedProperties.Clear();
RowType rowExprType = (RowType)rowExpr.ResultType.EdmType;
foreach (KeyValuePair<string, DbExpression> column in projectColumns)
{
EdmProperty prop = rowExprType.Properties[column.Key];
flattenedProperties.Add(resultBinding.Variable.Property(prop));
}
return resultBinding;
}
#endregion
}
}