Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Map / ViewGeneration / QueryRewriting / FragmentQueryProcessor.cs / 1305376 / FragmentQueryProcessor.cs
//---------------------------------------------------------------------- //// Copyright (c) Microsoft Corporation. All rights reserved. // // // @owner [....] // @backupOwner [....] //--------------------------------------------------------------------- using System; using System.Diagnostics; using System.Collections.Generic; using System.Text; using System.Data.Common.Utils; using System.Data.Common.Utils.Boolean; using System.Data.Mapping.ViewGeneration.Structures; using System.Data.Metadata.Edm; using System.Linq; using System.Globalization; namespace System.Data.Mapping.ViewGeneration.QueryRewriting { using BoolDomainConstraint = DomainConstraint; internal class FragmentQueryProcessor : TileQueryProcessor { private FragmentQueryKB _kb; public FragmentQueryProcessor(FragmentQueryKB kb) { _kb = kb; } internal static FragmentQueryProcessor Merge(FragmentQueryProcessor qp1, FragmentQueryProcessor qp2) { FragmentQueryKB mergedKB = new FragmentQueryKB(); mergedKB.AddKnowledgeBase(qp1.KnowledgeBase); mergedKB.AddKnowledgeBase(qp2.KnowledgeBase); return new FragmentQueryProcessor(mergedKB); } internal FragmentQueryKB KnowledgeBase { get { return _kb; } } // resulting query contains an intersection of attributes internal override FragmentQuery Union(FragmentQuery q1, FragmentQuery q2) { HashSet attributes = new HashSet (q1.Attributes); attributes.IntersectWith(q2.Attributes); BoolExpression condition = BoolExpression.CreateOr(q1.Condition, q2.Condition); return FragmentQuery.Create(attributes, condition); } internal bool IsDisjointFrom(FragmentQuery q1, FragmentQuery q2) { return !IsSatisfiable(Intersect(q1, q2)); } internal bool IsContainedIn(FragmentQuery q1, FragmentQuery q2) { return !IsSatisfiable(Difference(q1, q2)); } internal bool IsEquivalentTo(FragmentQuery q1, FragmentQuery q2) { return IsContainedIn(q1, q2) && IsContainedIn(q2, q1); } internal override FragmentQuery Intersect(FragmentQuery q1, FragmentQuery q2) { HashSet attributes = new HashSet (q1.Attributes); attributes.IntersectWith(q2.Attributes); BoolExpression condition = BoolExpression.CreateAnd(q1.Condition, q2.Condition); return FragmentQuery.Create(attributes, condition); } internal override FragmentQuery Difference(FragmentQuery qA, FragmentQuery qB) { return FragmentQuery.Create(qA.Attributes, BoolExpression.CreateAndNot(qA.Condition, qB.Condition)); } internal override bool IsSatisfiable(FragmentQuery query) { return IsSatisfiable(query.Condition); } private bool IsSatisfiable(BoolExpression condition) { // instantiate conversion context for each check - gives better performance BoolExpression conditionUnderKB = condition.Create( new AndExpr (_kb.KbExpression, condition.Tree)); var context = IdentifierService .Instance.CreateConversionContext(); var converter = new Converter (conditionUnderKB.Tree, context); bool isSatisfiable = converter.Vertex.IsZero() == false; return isSatisfiable; } // creates "derived" views that may be helpful for answering the query // for example, view = SELECT ID WHERE B=2, query = SELECT ID,B WHERE B=2 // Created derived view: SELECT ID,B WHERE B=2 by adding the attribute whose value is determined by the where clause to projected list internal override FragmentQuery CreateDerivedViewBySelectingConstantAttributes(FragmentQuery view) { HashSet newProjectedAttributes = new HashSet (); // collect all variables from the view IEnumerable > variables = view.Condition.Variables; foreach (DomainVariable var in variables) { MemberRestriction variableCondition = var.Identifier as MemberRestriction; if (variableCondition != null) { // Is this attribute not already projected? MemberPath conditionMember = variableCondition.RestrictedMemberSlot.MemberPath; // Iterating through the variable domain var.Domain could be wasteful // Instead, consider the actual condition values on the variable. Usually, they don't get repeated (if not, we could cache and check) Domain conditionValues = variableCondition.Domain; if ((false == view.Attributes.Contains(conditionMember)) && !(conditionValues.AllPossibleValues.Any(it => it.HasNotNull()))) //Don't add member to the projected list if the condition involves a { foreach (Constant value in conditionValues.Values) { // construct constraint: X = value DomainConstraint constraint = new DomainConstraint (var, new Set (new Constant[] { value }, Constant.EqualityComparer)); // is this constraint implied by the where clause? BoolExpression exclusion = view.Condition.Create( new AndExpr >(view.Condition.Tree, new NotExpr >(new TermExpr >(constraint)))); bool isImplied = false == IsSatisfiable(exclusion); if (isImplied) { // add this variable to the projection, if it is used in the query newProjectedAttributes.Add(conditionMember); } } } } } if (newProjectedAttributes.Count > 0) { newProjectedAttributes.UnionWith(view.Attributes); FragmentQuery derivedView = new FragmentQuery(String.Format(CultureInfo.InvariantCulture, "project({0})", view.Description), view.FromVariable, newProjectedAttributes, view.Condition); return derivedView; } return null; } public override string ToString() { return _kb.ToString(); } #region Private class AttributeSetComparator private class AttributeSetComparator : IEqualityComparer > { internal static readonly AttributeSetComparator DefaultInstance = new AttributeSetComparator(); #region IEqualityComparer > Members public bool Equals(HashSet x, HashSet y) { return x.SetEquals(y); } public int GetHashCode(HashSet attrs) { int hashCode = 123; foreach (MemberPath attr in attrs) { hashCode += MemberPath.EqualityComparer.GetHashCode(attr) * 7; } return hashCode; } #endregion } #endregion } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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