Imported Upstream version 3.6.0

Former-commit-id: da6be194a6b1221998fc28233f2503bd61dd9d14

external/entityframework/samples/Provider/SampleEntityFrameworkProvider/SqlGeneration/ISqlFragment.cs

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+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+using System.Data.SqlClient;
+using System.Data.Metadata.Edm;
+using System.Data.Common.CommandTrees;
+
+namespace SampleEntityFrameworkProvider
+{
+    /// <summary>
+    /// Represents the sql fragment for any node in the query tree.
+    /// </summary>
+    /// <remarks>
+    /// The nodes in a query tree produce various kinds of sql
+    /// <list type="bullet">
+    /// <item>A select statement.</item>
+    /// <item>A reference to an extent. (symbol)</item>
+    /// <item>A raw string.</item>
+    /// </list>
+    /// We have this interface to allow for a common return type for the methods
+    /// in the expression visitor <see cref="DbExpressionVisitor{T}"/>
+    /// 
+    /// At the end of translation, the sql fragments are converted into real strings.
+    /// </remarks>
+    internal interface ISqlFragment
+    {
+        /// <summary>
+        /// Write the string represented by this fragment into the stream.
+        /// </summary>
+        /// <param name="writer">The stream that collects the strings.</param>
+        /// <param name="sqlGenerator">Context information used for renaming.
+        /// The global lists are used to generated new names without collisions.</param>
+        void WriteSql(SqlWriter writer, SqlGenerator sqlGenerator);
+    }
+}

external/entityframework/samples/Provider/SampleEntityFrameworkProvider/SqlGeneration/JoinSymbol.cs

@@ -0,0 +1,93 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+using System.Data.SqlClient;
+using System.Data.Metadata.Edm;
+using System.Data.Common.CommandTrees;
+
+namespace SampleEntityFrameworkProvider
+{
+    /// <summary>
+    /// A Join symbol is a special kind of Symbol.
+    /// It has to carry additional information
+    /// <list type="bullet">
+    /// <item>ColumnList for the list of columns in the select clause if this
+    /// symbol represents a sql select statement.  This is set by <see cref="SqlGenerator.AddDefaultColumns"/>. </item>
+    /// <item>ExtentList is the list of extents in the select clause.</item>
+    /// <item>FlattenedExtentList - if the Join has multiple extents flattened at the 
+    /// top level, we need this information to ensure that extent aliases are renamed
+    /// correctly in <see cref="SqlSelectStatement.WriteSql"/></item>
+    /// <item>NameToExtent has all the extents in ExtentList as a dictionary.
+    /// This is used by <see cref="SqlGenerator.Visit(DbPropertyExpression)"/> to flatten
+    /// record accesses.</item>
+    /// <item>IsNestedJoin - is used to determine whether a JoinSymbol is an 
+    /// ordinary join symbol, or one that has a corresponding SqlSelectStatement.</item>
+    /// </list>
+    /// 
+    /// All the lists are set exactly once, and then used for lookups/enumerated.
+    /// </summary>
+    internal sealed class JoinSymbol : Symbol
+    {
+        private List<Symbol> columnList;
+        internal List<Symbol> ColumnList
+        {
+            get
+            {
+                if (null == columnList)
+                {
+                    columnList = new List<Symbol>();
+                }
+                return columnList;
+            }
+            set { columnList = value; }
+        }
+
+        private List<Symbol> extentList;
+        internal List<Symbol> ExtentList
+        {
+            get { return extentList; }
+        }
+
+        private List<Symbol> flattenedExtentList;
+        internal List<Symbol> FlattenedExtentList
+        {
+            get
+            {
+                if (null == flattenedExtentList)
+                {
+                    flattenedExtentList = new List<Symbol>();
+                }
+                return flattenedExtentList;
+            }
+            set { flattenedExtentList = value; }
+        }
+
+        private Dictionary<string, Symbol> nameToExtent;
+        internal Dictionary<string, Symbol> NameToExtent
+        {
+            get { return nameToExtent; }
+        }
+
+        private bool isNestedJoin;
+        internal bool IsNestedJoin
+        {
+            get { return isNestedJoin; }
+            set { isNestedJoin = value; }
+        }
+
+        public JoinSymbol(string name, TypeUsage type, List<Symbol> extents)
+            : base(name, type)
+        {
+            extentList = new List<Symbol>(extents.Count);
+            nameToExtent = new Dictionary<string, Symbol>(extents.Count, StringComparer.OrdinalIgnoreCase);
+            foreach (Symbol symbol in extents)
+            {
+                this.nameToExtent[symbol.Name] = symbol;
+                this.ExtentList.Add(symbol);
+            }
+        }
+    }
+}

external/entityframework/samples/Provider/SampleEntityFrameworkProvider/SqlGeneration/SqlBuilder.cs

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+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+using System.Data.SqlClient;
+using System.Data.Metadata.Edm;
+using System.Data.Common.CommandTrees;
+
+namespace SampleEntityFrameworkProvider
+{
+    /// <summary>
+    /// This class is like StringBuilder.  While traversing the tree for the first time, 
+    /// we do not know all the strings that need to be appended e.g. things that need to be
+    /// renamed, nested select statements etc.  So, we use a builder that can collect
+    /// all kinds of sql fragments.
+    /// </summary>
+    internal sealed class SqlBuilder : ISqlFragment
+    {
+        private List<object> _sqlFragments;
+        private List<object> sqlFragments
+        {
+            get
+            {
+                if (null == _sqlFragments)
+                {
+                    _sqlFragments = new List<object>();
+                }
+                return _sqlFragments;
+            }
+        }
+
+
+        /// <summary>
+        /// Add an object to the list - we do not verify that it is a proper sql fragment
+        /// since this is an internal method.
+        /// </summary>
+        /// <param name="s"></param>
+        public void Append(object s)
+        {
+            Debug.Assert(s != null);
+            sqlFragments.Add(s);
+        }
+
+        /// <summary>
+        /// This is to pretty print the SQL.  The writer <see cref="SqlWriter.Write"/>
+        /// needs to know about new lines so that it can add the right amount of 
+        /// indentation at the beginning of lines.
+        /// </summary>
+        public void AppendLine()
+        {
+            sqlFragments.Add("\r\n");
+        }
+
+        /// <summary>
+        /// Whether the builder is empty.  This is used by the <see cref="SqlGenerator.Visit(DbProjectExpression)"/>
+        /// to determine whether a sql statement can be reused.
+        /// </summary>
+        public bool IsEmpty
+        {
+            get { return ((null == _sqlFragments) || (0 == _sqlFragments.Count)); }
+        }
+
+        #region ISqlFragment Members
+
+        /// <summary>
+        /// We delegate the writing of the fragment to the appropriate type.
+        /// </summary>
+        /// <param name="writer"></param>
+        /// <param name="sqlGenerator"></param>
+        public void WriteSql(SqlWriter writer, SqlGenerator sqlGenerator)
+        {
+            if (null != _sqlFragments)
+            {
+                foreach (object o in _sqlFragments)
+                {
+                    string str = (o as String);
+                    if (null != str)
+                    {
+                        writer.Write(str);
+                    }
+                    else
+                    {
+                        ISqlFragment sqlFragment = (o as ISqlFragment);
+                        if (null != sqlFragment)
+                        {
+                            sqlFragment.WriteSql(writer, sqlGenerator);
+                        }
+                        else
+                        {
+                            throw new InvalidOperationException();
+                        }
+                    }
+                }
+            }
+        }
+
+        #endregion
+    }
+}

external/entityframework/samples/Provider/SampleEntityFrameworkProvider/SqlGeneration/SqlGenerator.cs.REMOVED.git-id

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+004b900742bebae9f8e3fdc3c947da685939f397

external/entityframework/samples/Provider/SampleEntityFrameworkProvider/SqlGeneration/SqlSelectStatement.cs

@@ -0,0 +1,308 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+using System.Data.SqlClient;
+using System.Data.Metadata.Edm;
+using System.Data.Common.CommandTrees;
+
+namespace SampleEntityFrameworkProvider
+{
+    /// <summary>
+    /// A SqlSelectStatement represents a canonical SQL SELECT statement.
+    /// It has fields for the 5 main clauses
+    /// <list type="number">
+    /// <item>SELECT</item>
+    /// <item>FROM</item>
+    /// <item>WHERE</item>
+    /// <item>GROUP BY</item>
+    /// <item>ORDER BY</item>
+    /// </list>
+    /// We do not have HAVING, since it does not correspond to anything in the DbCommandTree.
+    /// Each of the fields is a SqlBuilder, so we can keep appending SQL strings
+    /// or other fragments to build up the clause.
+    ///
+    /// We have a IsDistinct property to indicate that we want distict columns.
+    /// This is given out of band, since the input expression to the select clause
+    /// may already have some columns projected out, and we use append-only SqlBuilders.
+    /// The DISTINCT is inserted when we finally write the object into a string.
+    /// 
+    /// Also, we have a Top property, which is non-null if the number of results should
+    /// be limited to certain number. It is given out of band for the same reasons as DISTINCT.
+    ///
+    /// The FromExtents contains the list of inputs in use for the select statement.
+    /// There is usually just one element in this - Select statements for joins may
+    /// temporarily have more than one.
+    ///
+    /// If the select statement is created by a Join node, we maintain a list of
+    /// all the extents that have been flattened in the join in AllJoinExtents
+    /// <example>
+    /// in J(j1= J(a,b), c)
+    /// FromExtents has 2 nodes JoinSymbol(name=j1, ...) and Symbol(name=c)
+    /// AllJoinExtents has 3 nodes Symbol(name=a), Symbol(name=b), Symbol(name=c)
+    /// </example>
+    ///
+    /// If any expression in the non-FROM clause refers to an extent in a higher scope,
+    /// we add that extent to the OuterExtents list.  This list denotes the list
+    /// of extent aliases that may collide with the aliases used in this select statement.
+    /// It is set by <see cref="SqlGenerator.Visit(DbVariableReferenceExpression)"/>.
+    /// An extent is an outer extent if it is not one of the FromExtents.
+    ///
+    ///
+    /// </summary>
+    internal sealed class SqlSelectStatement : ISqlFragment
+    {
+        private bool isDistinct;
+
+        /// <summary>
+        /// Do we need to add a DISTINCT at the beginning of the SELECT
+        /// </summary>
+        internal bool IsDistinct
+        {
+            get { return isDistinct; }
+            set { isDistinct = value; }
+        }
+
+        private List<Symbol> allJoinExtents;
+        internal List<Symbol> AllJoinExtents
+        {
+            get { return allJoinExtents; }
+            // We have a setter as well, even though this is a list,
+            // since we use this field only in special cases.
+            set { allJoinExtents = value; }
+        }
+
+        private List<Symbol> fromExtents;
+        internal List<Symbol> FromExtents
+        {
+            get
+            {
+                if (null == fromExtents)
+                {
+                    fromExtents = new List<Symbol>();
+                }
+                return fromExtents;
+            }
+        }
+
+        private Dictionary<Symbol, bool> outerExtents;
+        internal Dictionary<Symbol, bool> OuterExtents
+        {
+            get
+            {
+                if (null == outerExtents)
+                {
+                    outerExtents = new Dictionary<Symbol, bool>();
+                }
+                return outerExtents;
+            }
+        }
+
+        private TopClause top;
+        internal TopClause Top
+        {
+            get { return top; }
+            set 
+            {
+                Debug.Assert(top == null, "SqlSelectStatement.Top has already been set");
+                top = value; 
+            }
+        }
+
+        private SqlBuilder select = new SqlBuilder();
+        internal SqlBuilder Select
+        {
+            get { return select; }
+        }
+
+        private SqlBuilder from = new SqlBuilder();
+        internal SqlBuilder From
+        {
+            get { return from; }
+        }
+
+
+        private SqlBuilder where;
+        internal SqlBuilder Where
+        {
+            get
+            {
+                if (null == where)
+                {
+                    where = new SqlBuilder();
+                }
+                return where;
+            }
+        }
+
+        private SqlBuilder groupBy;
+        internal SqlBuilder GroupBy
+        {
+            get
+            {
+                if (null == groupBy)
+                {
+                    groupBy = new SqlBuilder();
+                }
+                return groupBy;
+            }
+        }
+
+        private SqlBuilder orderBy;
+        public SqlBuilder OrderBy
+        {
+            get
+            {
+                if (null == orderBy)
+                {
+                    orderBy = new SqlBuilder();
+                }
+                return orderBy;
+            }
+        }
+
+        //indicates whether it is the top most select statement, 
+        // if not Order By should be omitted unless there is a corresponding TOP
+        private bool isTopMost;
+        internal bool IsTopMost
+        {
+            get { return this.isTopMost; }
+            set { this.isTopMost = value; }
+        }
+
+        #region ISqlFragment Members
+
+        /// <summary>
+        /// Write out a SQL select statement as a string.
+        /// We have to
+        /// <list type="number">
+        /// <item>Check whether the aliases extents we use in this statement have
+        /// to be renamed.
+        /// We first create a list of all the aliases used by the outer extents.
+        /// For each of the FromExtents( or AllJoinExtents if it is non-null),
+        /// rename it if it collides with the previous list.
+        /// </item>
+        /// <item>Write each of the clauses (if it exists) as a string</item>
+        /// </list>
+        /// </summary>
+        /// <param name="writer"></param>
+        /// <param name="sqlGenerator"></param>
+        public void WriteSql(SqlWriter writer, SqlGenerator sqlGenerator)
+        {
+            #region Check if FROM aliases need to be renamed
+
+            // Create a list of the aliases used by the outer extents
+            // JoinSymbols have to be treated specially.
+            List<string> outerExtentAliases = null;
+            if ((null != outerExtents) && (0 < outerExtents.Count))
+            {
+                foreach (Symbol outerExtent in outerExtents.Keys)
+                {
+                    JoinSymbol joinSymbol = outerExtent as JoinSymbol;
+                    if (joinSymbol != null)
+                    {
+                        foreach (Symbol symbol in joinSymbol.FlattenedExtentList)
+                        {
+                            if (null == outerExtentAliases) { outerExtentAliases = new List<string>(); }
+                            outerExtentAliases.Add(symbol.NewName);
+                        }
+                    }
+                    else
+                    {
+                        if (null == outerExtentAliases) { outerExtentAliases = new List<string>(); }
+                        outerExtentAliases.Add(outerExtent.NewName);
+                    }
+                }
+            }        
+
+            // An then rename each of the FromExtents we have
+            // If AllJoinExtents is non-null - it has precedence.
+            // The new name is derived from the old name - we append an increasing int.
+            List<Symbol> extentList = this.AllJoinExtents ?? this.fromExtents;
+            if (null != extentList)
+            {
+                foreach (Symbol fromAlias in extentList)
+                {
+                    if ((null != outerExtentAliases) && outerExtentAliases.Contains(fromAlias.Name))
+                    {
+                        int i = sqlGenerator.AllExtentNames[fromAlias.Name];
+                        string newName;
+                        do
+                        {
+                            ++i;
+                            newName = fromAlias.Name + i.ToString(System.Globalization.CultureInfo.InvariantCulture);
+                        }
+                        while (sqlGenerator.AllExtentNames.ContainsKey(newName));
+                        sqlGenerator.AllExtentNames[fromAlias.Name] = i;
+                        fromAlias.NewName = newName;
+
+                        // Add extent to list of known names (although i is always incrementing, "prefix11" can
+                        // eventually collide with "prefix1" when it is extended)
+                        sqlGenerator.AllExtentNames[newName] = 0;
+                    }
+
+                    // Add the current alias to the list, so that the extents
+                    // that follow do not collide with me.
+                    if (null == outerExtentAliases) { outerExtentAliases = new List<string>(); }
+                    outerExtentAliases.Add(fromAlias.NewName);
+                }
+            }
+            #endregion
+
+            // Increase the indent, so that the Sql statement is nested by one tab.
+            writer.Indent += 1; // ++ can be confusing in this context
+
+            writer.Write("SELECT ");
+            if (IsDistinct)
+            {
+                writer.Write("DISTINCT ");
+            }
+
+            if (this.Top != null)
+            {
+                this.Top.WriteSql(writer, sqlGenerator);
+            }
+
+            if ((null == this.select) || this.Select.IsEmpty)
+            {
+                Debug.Assert(false);  // we have removed all possibilities of SELECT *.
+                writer.Write("*");
+            }
+            else
+            {
+                this.Select.WriteSql(writer, sqlGenerator);
+            }
+
+            writer.WriteLine();
+            writer.Write("FROM ");
+            this.From.WriteSql(writer, sqlGenerator);
+
+            if ((null != this.where) && !this.Where.IsEmpty)
+            {
+                writer.WriteLine();
+                writer.Write("WHERE ");
+                this.Where.WriteSql(writer, sqlGenerator);
+            }
+
+            if ((null != this.groupBy) && !this.GroupBy.IsEmpty)
+            {
+                writer.WriteLine();
+                writer.Write("GROUP BY ");
+                this.GroupBy.WriteSql(writer, sqlGenerator);
+            }
+
+            if ((null != this.orderBy) && !this.OrderBy.IsEmpty && (this.IsTopMost || this.Top != null))
+            {
+                writer.WriteLine();
+                writer.Write("ORDER BY ");
+                this.OrderBy.WriteSql(writer, sqlGenerator);
+            }
+
+            --writer.Indent;
+        }
+
+        #endregion
+    }
+}

external/entityframework/samples/Provider/SampleEntityFrameworkProvider/SqlGeneration/SqlWriter.cs

@@ -0,0 +1,78 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+using System.Data.SqlClient;
+using System.Data.Metadata.Edm;
+using System.Data.Common.CommandTrees;
+
+namespace SampleEntityFrameworkProvider
+{
+    /// <summary>
+    /// This extends StringWriter primarily to add the ability to add an indent
+    /// to each line that is written out.
+    /// </summary>
+    class SqlWriter : StringWriter
+    {
+        // We start at -1, since the first select statement will increment it to 0.
+        int indent = -1;
+        /// <summary>
+        /// The number of tabs to be added at the beginning of each new line.
+        /// </summary>
+        internal int Indent
+        {
+            get { return indent; }
+            set { indent = value; }
+        }
+
+        bool atBeginningOfLine = true;
+
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="b"></param>
+        public SqlWriter(StringBuilder b)
+            : base(b, System.Globalization.CultureInfo.InvariantCulture)
+        {
+        }
+
+        /// <summary>
+        /// Reset atBeginningofLine if we detect the newline string.
+        /// <see cref="SqlBuilder.AppendLine"/>
+        /// Add as many tabs as the value of indent if we are at the 
+        /// beginning of a line.
+        /// </summary>
+        /// <param name="value"></param>
+        public override void Write(string value)
+        {
+            if (value == "\r\n")
+            {
+                base.WriteLine();
+                atBeginningOfLine = true;
+            }
+            else
+            {
+                if (atBeginningOfLine)
+                {
+                    if (indent > 0)
+                    {
+                        base.Write(new string('\t', indent));
+                    }
+                    atBeginningOfLine = false;
+                }
+                base.Write(value);
+            }
+        }
+
+        /// <summary>
+        /// 
+        /// </summary>
+        public override void WriteLine()
+        {
+            base.WriteLine();
+            atBeginningOfLine = true;
+        }
+    }
+}

external/entityframework/samples/Provider/SampleEntityFrameworkProvider/SqlGeneration/Symbol.cs

@@ -0,0 +1,116 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+using System.Data.SqlClient;
+using System.Data.Metadata.Edm;
+using System.Data.Common.CommandTrees;
+
+namespace SampleEntityFrameworkProvider
+{
+    /// <summary>
+    /// <see cref="SymbolTable"/>
+    /// This class represents an extent/nested select statement,
+    /// or a column.
+    ///
+    /// The important fields are Name, Type and NewName.
+    /// NewName starts off the same as Name, and is then modified as necessary.
+    ///
+    ///
+    /// The rest are used by special symbols.
+    /// e.g. NeedsRenaming is used by columns to indicate that a new name must
+    /// be picked for the column in the second phase of translation.
+    ///
+    /// IsUnnest is used by symbols for a collection expression used as a from clause.
+    /// This allows <see cref="SqlGenerator.AddFromSymbol(SqlSelectStatement, string, Symbol, bool)"/> to add the column list
+    /// after the alias.
+    ///
+    /// </summary>
+    class Symbol : ISqlFragment
+    {
+        private Dictionary<string, Symbol> columns = new Dictionary<string, Symbol>(StringComparer.CurrentCultureIgnoreCase);
+        internal Dictionary<string, Symbol> Columns
+        {
+            get { return columns; }
+        }
+
+        private bool needsRenaming = false;
+        internal bool NeedsRenaming
+        {
+            get { return needsRenaming; }
+            set { needsRenaming = value; }
+        }
+
+        bool isUnnest = false;
+        internal bool IsUnnest
+        {
+            get { return isUnnest; }
+            set { isUnnest = value; }
+        }
+
+        string name;
+        public string Name
+        {
+            get { return name; }
+        }
+
+        string newName;
+        public string NewName
+        {
+            get { return newName; }
+            set { newName = value; }
+        }
+
+        private TypeUsage type;
+        internal TypeUsage Type
+        {
+            get { return type; }
+            set { type = value; }
+        }
+
+        public Symbol(string name, TypeUsage type)
+        {
+            this.name = name;
+            this.newName = name;
+            this.Type = type;
+        }
+
+        #region ISqlFragment Members
+
+        /// <summary>
+        /// Write this symbol out as a string for sql.  This is just
+        /// the new name of the symbol (which could be the same as the old name).
+        ///
+        /// We rename columns here if necessary.
+        /// </summary>
+        /// <param name="writer"></param>
+        /// <param name="sqlGenerator"></param>
+        public void WriteSql(SqlWriter writer, SqlGenerator sqlGenerator)
+        {
+            if (this.NeedsRenaming)
+            {
+                string newName;
+                int i = sqlGenerator.AllColumnNames[this.NewName];
+                do
+                {
+                    ++i;
+                    newName = this.Name + i.ToString(System.Globalization.CultureInfo.InvariantCulture);
+                } while (sqlGenerator.AllColumnNames.ContainsKey(newName));
+                sqlGenerator.AllColumnNames[this.NewName] = i;
+
+                // Prevent it from being renamed repeatedly.
+                this.NeedsRenaming = false;
+                this.NewName = newName;
+
+                // Add this column name to list of known names so that there are no subsequent
+                // collisions
+                sqlGenerator.AllColumnNames[newName] = 0;
+            }
+            writer.Write(SqlGenerator.QuoteIdentifier(this.NewName));
+        }
+
+        #endregion
+    }
+}

external/entityframework/samples/Provider/SampleEntityFrameworkProvider/SqlGeneration/SymbolPair.cs

@@ -0,0 +1,50 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+using System.Data.SqlClient;
+using System.Data.Metadata.Edm;
+using System.Data.Common.CommandTrees;
+
+namespace SampleEntityFrameworkProvider
+{
+    /// <summary>
+    /// The SymbolPair exists to solve the record flattening problem.
+    /// <see cref="SqlGenerator.Visit(DbPropertyExpression)"/>
+    /// Consider a property expression D(v, "j3.j2.j1.a.x")
+    /// where v is a VarRef, j1, j2, j3 are joins, a is an extent and x is a columns.
+    /// This has to be translated eventually into {j'}.{x'}
+    /// 
+    /// The source field represents the outermost SqlStatement representing a join
+    /// expression (say j2) - this is always a Join symbol.
+    /// 
+    /// The column field keeps moving from one join symbol to the next, until it
+    /// stops at a non-join symbol.
+    /// 
+    /// This is returned by <see cref="SqlGenerator.Visit(DbPropertyExpression)"/>,
+    /// but never makes it into a SqlBuilder.
+    /// </summary>
+    class SymbolPair : ISqlFragment
+    {
+        public Symbol Source;
+        public Symbol Column;
+
+        public SymbolPair(Symbol source, Symbol column)
+        {
+            this.Source = source;
+            this.Column = column;
+        }
+
+        #region ISqlFragment Members
+
+        public void WriteSql(SqlWriter writer, SqlGenerator sqlGenerator)
+        {
+            // Symbol pair should never be part of a SqlBuilder.
+            Debug.Assert(false);
+        }
+
+        #endregion
+    }
+}

external/entityframework/samples/Provider/SampleEntityFrameworkProvider/SqlGeneration/SymbolTable.cs

@@ -0,0 +1,60 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+using System.Data.SqlClient;
+using System.Data.Metadata.Edm;
+using System.Data.Common.CommandTrees;
+
+namespace SampleEntityFrameworkProvider
+{
+    /// <summary>
+    /// The symbol table is quite primitive - it is a stack with a new entry for
+    /// each scope.  Lookups search from the top of the stack to the bottom, until
+    /// an entry is found.
+    /// 
+    /// The symbols are of the following kinds
+    /// <list type="bullet">
+    /// <item><see cref="Symbol"/> represents tables (extents/nested selects/unnests)</item>
+    /// <item><see cref="JoinSymbol"/> represents Join nodes</item>
+    /// <item><see cref="Symbol"/> columns.</item>
+    /// </list>
+    /// 
+    /// Symbols represent names <see cref="SqlGenerator.Visit(DbVariableReferenceExpression)"/> to be resolved, 
+    /// or things to be renamed.
+    /// </summary>
+    internal sealed class SymbolTable
+    {
+        private List<Dictionary<string, Symbol>> symbols = new List<Dictionary<string, Symbol>>();
+
+        internal void EnterScope()
+        {
+            symbols.Add(new Dictionary<string, Symbol>(StringComparer.OrdinalIgnoreCase));
+        }
+
+        internal void ExitScope()
+        {
+            symbols.RemoveAt(symbols.Count - 1);
+        }
+
+        internal void Add(string name, Symbol value)
+        {
+            symbols[symbols.Count - 1][name] = value;
+        }
+
+        internal Symbol Lookup(string name)
+        {
+            for (int i = symbols.Count - 1; i >= 0; --i)
+            {
+                if (symbols[i].ContainsKey(name))
+                {
+                    return symbols[i][name];
+                }
+            }
+
+            return null;
+        }
+    }
+}

external/entityframework/samples/Provider/SampleEntityFrameworkProvider/SqlGeneration/TopClause.cs

@@ -0,0 +1,88 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Globalization;
+using System.IO;
+using System.Text;
+using System.Data.SqlClient;
+using System.Data.Metadata.Edm;
+using System.Data.Common.CommandTrees;
+
+namespace SampleEntityFrameworkProvider
+{
+    /// <summary>
+    /// TopClause represents the a TOP expression in a SqlSelectStatement. 
+    /// It has a count property, which indicates how many TOP rows should be selected and a 
+    /// boolen WithTies property.
+    /// </summary>
+    class TopClause : ISqlFragment
+    {
+        ISqlFragment topCount;
+        bool withTies;
+
+        /// <summary>
+        /// Do we need to add a WITH_TIES to the top statement
+        /// </summary>
+        internal bool WithTies
+        {
+            get { return withTies; }
+        }
+
+        /// <summary>
+        /// How many top rows should be selected.
+        /// </summary>
+        internal ISqlFragment TopCount
+        {
+            get { return topCount; }
+        }
+
+        /// <summary>
+        /// Creates a TopClause with the given topCount and withTies.
+        /// </summary>
+        /// <param name="topCount"></param>
+        /// <param name="withTies"></param>
+        internal TopClause(ISqlFragment topCount, bool withTies)
+        {
+            this.topCount = topCount;
+            this.withTies = withTies;
+        }
+
+        /// <summary>
+        /// Creates a TopClause with the given topCount and withTies.
+        /// </summary>
+        /// <param name="topCount"></param>
+        /// <param name="withTies"></param>
+        internal TopClause(int topCount, bool withTies)
+        {
+            SqlBuilder sqlBuilder = new SqlBuilder();
+            sqlBuilder.Append(topCount.ToString(CultureInfo.InvariantCulture));
+            this.topCount = sqlBuilder;
+            this.withTies = withTies;
+        }
+
+        #region ISqlFragment Members
+
+        /// <summary>
+        /// Write out the TOP part of sql select statement 
+        /// It basically writes TOP (X) [WITH TIES].
+        /// </summary>
+        /// <param name="writer"></param>
+        /// <param name="sqlGenerator"></param>
+        public void WriteSql(SqlWriter writer, SqlGenerator sqlGenerator)
+        {
+            writer.Write("TOP (");
+            this.TopCount.WriteSql(writer, sqlGenerator);
+            writer.Write(")");
+
+            writer.Write(" ");
+
+            if (this.WithTies)
+            {
+                writer.Write("WITH TIES ");
+            }
+        }
+
+        #endregion
+    }
+}