EntitySqlQueryState.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Objects / Internal / EntitySqlQueryState.cs / 1305376 / EntitySqlQueryState.cs
                        
                        
                            //---------------------------------------------------------------------- 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// 
// @owner  [....]
//--------------------------------------------------------------------- 
 
using System.Collections.Generic;
using System.Data.Common; 
using System.Data.Common.CommandTrees;
using System.Data.Common.CommandTrees.ExpressionBuilder;
using System.Data.Common.EntitySql;
using System.Data.Common.QueryCache; 
using System.Data.Common.Utils;
using System.Data.EntityClient; 
using System.Data.Metadata.Edm; 
using System.Data.Objects.Internal;
using System.Diagnostics; 

namespace System.Data.Objects
{
    ///  
    /// ObjectQueryState based on Entity-SQL query text.
    ///  
    internal sealed class EntitySqlQueryState : ObjectQueryState 
    {
        ///  
        ///     The Entity-SQL text that defines the query.
        /// 
        private readonly string _queryText;
 
        /// 
        ///     Can a Limit subclause be appended to the text of this query? 
        ///  
        private readonly bool _allowsLimit;
 
        /// 
        /// Initializes a new query EntitySqlQueryState instance.
        /// 
        ///  
        ///     The ObjectContext containing the metadata workspace the query was
        ///     built against, the connection on which to execute the query, and the 
        ///     cache to store the results in. Must not be null. 
        /// 
        ///  
        ///     The Entity-SQL text of the query
        /// 
        /// 
        ///     The merge option to use when retrieving results if an explicit merge option is not specified 
        /// 
        internal EntitySqlQueryState(Type elementType, string commandText, bool allowsLimit, ObjectContext context, ObjectParameterCollection parameters, Span span) 
            : base(elementType, context, parameters, span) 
        {
            EntityUtil.CheckArgumentNull(commandText, "commandText"); 
            if (string.IsNullOrEmpty(commandText))
            {
                throw EntityUtil.Argument(System.Data.Entity.Strings.ObjectQuery_InvalidEmptyQuery, "commandText");
            } 

            _queryText = commandText; 
            _allowsLimit = allowsLimit; 
        }
 
        /// 
        ///     Determines whether or not the current query is a 'Skip' or 'Sort' operation
        ///     and so would allow a 'Limit' clause to be appended to the current query text.
        ///  
        /// 
        ///     True if the current query is a Skip or Sort expression, or a 
        ///     Project expression with a Skip or Sort expression input. 
        /// 
        internal bool AllowsLimitSubclause { get { return _allowsLimit; } } 

        /// 
        /// Always returns the Entity-SQL text of the implemented ObjectQuery.
        ///  
        /// Always set to the Entity-SQL text of this ObjectQuery.
        /// Always returns true. 
        internal override bool TryGetCommandText(out string commandText) 
        {
            commandText = this._queryText; 
            return true;
        }

        internal override bool TryGetExpression(out System.Linq.Expressions.Expression expression) 
        {
            expression = null; 
            return false; 
        }
 
        protected override TypeUsage GetResultType()
        {
            DbExpression query = this.Parse();
            return query.ResultType; 
        }
 
        internal override ObjectQueryState Include(ObjectQuery sourceQuery, string includePath) 
        {
            ObjectQueryState retState = new EntitySqlQueryState(this.ElementType, _queryText, _allowsLimit, this.ObjectContext, ObjectParameterCollection.DeepCopy(this.Parameters), Span.IncludeIn(this.Span, includePath)); 
            this.ApplySettingsTo(retState);
            return retState;
        }
 
        internal override ObjectQueryExecutionPlan GetExecutionPlan(MergeOption? forMergeOption)
        { 
            // Metadata is required to generate the execution plan or to retrieve it from the cache. 
            this.ObjectContext.EnsureMetadata();
 
            // Determine the required merge option, with the following precedence:
            // 1. The merge option specified to Execute(MergeOption) as forMergeOption.
            // 2. The merge option set via ObjectQuery.MergeOption.
            // 3. The global default merge option. 
            MergeOption mergeOption = EnsureMergeOption(forMergeOption, this.UserSpecifiedMergeOption);
 
            // If a cached plan is present, then it can be reused if it has the required merge option 
            // (since span and parameters cannot change between executions). However, if the cached
            // plan does not have the required merge option we proceed as if it were not present. 
            ObjectQueryExecutionPlan plan = this._cachedPlan;
            if (plan != null)
            {
                if (plan.MergeOption == mergeOption) 
                {
                    return plan; 
                } 
                else
                { 
                    plan = null;
                }
            }
 
            // There is no cached plan (or it was cleared), so the execution plan must be retrieved from
            // the global query cache (if plan caching is enabled) or rebuilt for the required merge option. 
            QueryCacheManager cacheManager = null; 
            EntitySqlQueryCacheKey cacheKey = null;
            if (this.PlanCachingEnabled) 
            {
                // Create a new cache key that reflects the current state of the Parameters collection
                // and the Span object (if any), and uses the specified merge option.
                cacheKey = new EntitySqlQueryCacheKey( 
                                   this.ObjectContext.DefaultContainerName,
                                   _queryText, 
                                   (null == this.Parameters ? 0 : this.Parameters.Count), 
                                   (null == this.Parameters ? null : this.Parameters.GetCacheKey()),
                                   (null == this.Span ? null : this.Span.GetCacheKey()), 
                                   mergeOption,
                                   this.ElementType);

                cacheManager = this.ObjectContext.MetadataWorkspace.GetQueryCacheManager(); 
                ObjectQueryExecutionPlan executionPlan = null;
                if (cacheManager.TryCacheLookup(cacheKey, out executionPlan)) 
                { 
                    plan = executionPlan;
                } 
            }

            if (plan == null)
            { 
                // Either caching is not enabled or the execution plan was not found in the cache
                DbExpression queryExpression = this.Parse(); 
                Debug.Assert(queryExpression != null, "EntitySqlQueryState.Parse returned null expression?"); 
                DbQueryCommandTree tree = DbQueryCommandTree.FromValidExpression(this.ObjectContext.MetadataWorkspace, DataSpace.CSpace, queryExpression);
                plan = ObjectQueryExecutionPlan.Prepare(this.ObjectContext, tree, this.ElementType, mergeOption, this.Span, null); 

                // If caching is enabled then update the cache now
                if (cacheKey != null)
                { 
                    EntitySqlQueryCacheEntry newEntry = new EntitySqlQueryCacheEntry(cacheKey, plan);
                    QueryCacheEntry foundEntry = null; 
                    if (cacheManager.TryLookupAndAdd(newEntry, out foundEntry)) 
                    {
                        // If TryLookupAndAdd returns 'true' then the entry was already present in the cache when the attempt to add was made. 
                        // In this case the existing execution plan should be used.
                        plan = ((EntitySqlQueryCacheEntry)foundEntry).ExecutionPlan;
                    }
                } 
            }
 
            if (this.Parameters != null) 
            {
                this.Parameters.SetReadOnly(true); 
            }

            // Update the cached plan with the newly retrieved/prepared plan
            this._cachedPlan = plan; 

            // Return the execution plan 
            return plan; 
        }
 
        internal DbExpression Parse()
        {
            List parameters = null;
            if (this.Parameters != null) 
            {
                parameters = new List(this.Parameters.Count); 
                foreach (ObjectParameter parameter in this.Parameters) 
                {
                    TypeUsage typeUsage = parameter.TypeUsage; 
                    if (null == typeUsage)
                    {
                        // Since ObjectParameters do not allow users to specify 'facets', make
                        // sure that the parameter TypeUsage is not populated with the provider 
                        // default facet values.
                        this.ObjectContext.Perspective.TryGetTypeByName( 
                                        parameter.MappableType.FullName, 
                                        false /* bIgnoreCase */,
                                        out typeUsage); 
                    }

                    Debug.Assert(typeUsage != null, "typeUsage != null");
 
                    parameters.Add(typeUsage.Parameter(parameter.Name));
                } 
            } 

            DbLambda lambda = 
                CqlQuery.CompileQueryCommandLambda(
                    _queryText,                     // Command Text
                    this.ObjectContext.Perspective, // Perspective
                    null,                           // Parser options - null indicates 'use default' 
                    parameters,                     // Parameters
                    null                            // Variables 
                ); 

            Debug.Assert(lambda.Variables == null || lambda.Variables.Count == 0, "lambda.Variables must be empty"); 

            return lambda.Body;
        }
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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EntitySqlQueryState.cs source code in C# .NET

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